毕业设计冷凝器外文翻译
模具毕业设计外文翻译(英文+译文)
Injection MoldingThe basic concept of injection molding revolves around the ability of a thermoplastic material to be softened by heat and to harden when cooled .In most operations ,granular material (the plastic resin) is fed into one end of the cylinder (usually through a feeding device known as a hopper ),heated, and softened(plasticized or plasticized),forced out the other end of the cylinder, while it is still in the form of a melt, through a nozzle into a relatively cool mold held closed under pressure.Here,the melt cools and hardens until fully set-up. The mold is then opened, the piece ejected, and the sequence repeated.Thus, the significant elements of an injection molding machine become: 1) the way in which the melt is plasticized (softened) and forced into the mold (called the injection unit);2) the system for opening the mold and closing it under pressure (called the clamping unit);3) the type of mold used;4) the machine controls.The part of an injection-molding machine, which converts a plastic material from a sold phase to homogeneous seni-liguid phase by raising its temperature .This unit maintains the material at a present temperature and force it through the injection unit nozzle into a mold .The plunger is a combination of the injection and plasticizing device in which a heating chamber is mounted between the plunger and mold. This chamber heats the plastic material by conduction .The plunger, on each stroke; pushes unbelted plastic material into the chamber, which in turn forces plastic melt at the front of the chamber out through the nozzleThe part of an injection molding machine in which the mold is mounted, and which provides the motion and force to open and close the mold and to hold the mold close with force during injection .This unit can also provide other features necessary for the effective functioning of the molding operation .Movingplate is the member of the clamping unit, which is moved toward a stationary member. the moving section of the mold is bolted to this moving plate .This member usually includes the ejector holes and mold mounting pattern of blot holes or “T” slots .Stationary plate is the fixed member of the clamping unit on which the stationary section of the mold is bolted .This member usually includes a mold-mounting pattern of boles or “T” slots. Tie rods are member of the clamping force actuating mechanism that serve as the tension member of the clamp when it is holding the mold closed. They also serve as a gutted member for the movable plate .Ejector is a provision in the clamping unit that actuates a mechanism within the mold to eject the molded part(s) from the mold .The ejection actuating force may be applied hydraulically or pneumatically by a cylinder(s) attached to the moving plate, or mechanically by the opening stroke of the moving plate.Methods of melting and injecting the plastic differ from one machine to another and are constantly being implored .conventional machines use a cylinder and piston to do both jobs .This method simplifies machine construction but makes control of injection temperatures and pressures an inherently difficult problem .Other machines use a plasticizing extruder to melt the plastic and piston to inject it while some hare been designed to use a screw for both jobs :Nowadays, sixty percent of the machines use a reciprocating screw,35% a plunger (concentrated in the smaller machine size),and 5%a screw pot.Many of the problems connected with in ejection molding arise because the densities of polymers change so markedly with temperature and pressure. thigh temperatures, the density of a polymer is considerably cower than at room temperature, provided the pressure is the same.Therefore,if molds were filled at atmospheric pressure, “shrinkage” would make the molding deviate form the shape of the mold.To compensate for this poor effect, molds are filled at high pressure. The pressure compresses the polymer and allows more materials to flow into the mold, shrinkage is reduced and better quality moldings are produced.Cludes a mold-mounting pattern of bolt holes or “T” slots. Tie rods are members of the clamping force actuating mechanism that serve as the tension members of clamp when it is holding the mold closed. Ejector is a provision in the calming unit that actuates a mechanism within the mold to eject the molded part(s) form the mold. The ejection actuating force may be applied hydraulically or pneumatically by a cylinder(s) attached to the moving plate, or mechanically by the opening stroke of the moving plate.The function of a mold is twofold: imparting the desired shape to the plasticized polymer and cooling the injection molded part. It is basically made up of two sets of components: the cavities and cores and the base in which the cavities and cores are mounted. The mold ,which contains one or more cavities, consists of two basic parts :(1) a stationary molds half one the side where the plastic is injected,(2)Moving half on the closing or ejector side of the machine. The separation between the two mold halves is called the parting line. In some cases the cavity is partly in the stationary and partly in the moving section. The size and weight of the molded parts limit the number of cavities in the mold and also determine the machinery capacity required. The mold components and their functions are as following:(1)Mold Base-Hold cavity (cavities) in fixed, correctposition relative to machine nozzle.(2)Guide Pins-Maintain Proper alignment of entry into moldinterior.(3)Spree Bushing (spree)-Provide means of entry into moldinterior.(4)Runners-Conroy molten plastic from spree to cavities.(5)Gates-Control flow into cavities.(6)Cavity (female) and Force (male)-Control the size,shape and surface of mold article.(7)Water Channels-Control the temperature of mold surfacesto chill plastic to rigid state.(8)Side (actuated by came, gears or hydrauliccylinders)-Form side holes, slots, undercuts and threaded sections.(9)Vent-Allow the escape of trapped air and gas.(10)Ejector Mechanism (pins, blades, stripper plate)-Ejectrigid molded article form cavity or force.(11)Ejector Return Pins-Return ejector pins to retractedposition as mold closes for next cycle.The distance between the outer cavities and the primary spree must not be so long that the molten plastic loses too much heat in the runner to fill the outer cavities properly. The cavities should be so arranged around the primary spree that each receives its full and equal share of the total pressure available, through its own runner system (or the so-called balanced runner system).The requires the shortest possible distance between cavities and primary sprue, equal runner and gate dimension, and uniform culling.注射成型注射成型的基本概念是使热塑性材料在受热时熔融，冷却时硬化，在大部分加工中，粒状材料（即塑料树脂）从料筒的一端（通常通过一个叫做“料斗”的进料装置）送进，受热并熔融（即塑化或增塑），然后当材料还是溶体时，通过一个喷嘴从料筒的另一端挤到一个相对较冷的压和封闭的模子里。
电气自动化专业毕业设计外文翻译(中英文对照翻译)-制冷压缩机速度的模糊控制
毕业设计（论文）外文翻译Fuzzy Control of The Compressor Speed in aRefrigeration plant制冷压缩机速度的模糊控制制冷压缩机速度的模糊控制摘要在这篇文章里，所提到的是在通常应用于商业上的蒸汽压缩制冷装之中，用模糊控制算法控制制冷压缩机的速度使之达到最有效的速度来控制冷气的温度。
它主要的目标是根据模糊控制算法，通过变换器对压缩机速度进行连续调控，并估算节能效果；不同于传统恒温控制，这里通过控制压缩机冷藏容量，施加给控制压缩机50Hz的开关运转频率。
通过控制压缩机的电动机的供电电流达到的速度变化范围是30-50Hz，由于转动频率过低会有因飞溅系统而出现的润滑问题，现今所提供的压缩机转动频率一般不考虑小于30Hz的。
在这个范围，在二个最适当的工作流体之中，可以代替R22有很多，例如R407C (R32/R125/R134a 23/25/52%组)和R507 (R125/R143A 50/50%组)比较好。
压缩机速度模糊控制与传统的温度控制相比，更多的用于冷藏和其他制冷系统。
实验结果表明，当R407C 作为工作流体时，可以达到显著的节能效果，( 13%)。
值得注意的是，从节能观点看，当压缩机速度变化时可以达到的最佳的效果。
另外，考虑到变换器费用问题，回收期要比可接受的产品型号更具有决定性。
关键词：压缩系统; 冷室; 活塞式压缩机; 易变的速度; 章程; 模糊逻辑;R407C; R5071引言蒸气压缩冷却装置，虽则被设计满足最大载荷，但为了延长寿命，通常在部分装载下工作，并通过开关周期调控，在50 Hz的频率下运作，这样就决定了高能消耗量的恒温控制。
而且，制冷时耗电量低被认为间接的释放了温室气体; 改进上述的系统的能量转换效率可以减少这种排放物。
各种各样的冷藏容量控制方法和部分装载理论表明压缩机速度变异是最高效率的技术。
[1,2]。
冷藏容量控制这个方法在最近3–10年已经被分析研究，包括提高压缩机的速度以不断的达到制冷效果。
暖通空调专业-毕业设计外文翻译
Refrigeration System Performance using Liquid-Suction Heat ExchangersS. A. Klein, D. T. Reindl, and K. BroWnellCollege of EngineeringUniversity of Wisconsin - MadisonAbstractHeat transfer devices are provided in many refrigeration systems to exchange energy betWeen the cool gaseous refrigerant leaving the evaporator and Warm liquid refrigerant exiting the condenser. These liquid-suction or suction-line heat exchangers can, in some cases, yield improved system performance While in other cases they degrade system performance. Although previous researchers have investigated performance of liquid-suction heat exchangers, this study can be distinguished from the previous studies in three Ways. First, this paper identifies a neW dimensionless group to correlate performance impacts attributable to liquid-suction heat exchangers. Second, the paper extends previous analyses to include neW refrigerants. Third, the analysis includes the impact of pressure drops through the liquid-suction heat exchanger on system performance. It is shoWn that reliance on simplified analysis techniques can lead to inaccurate conclusions regarding the impact of liquid-suction heat exchangers on refrigeration system performance. From detailed analyses, it can be concluded that liquid-suction heat exchangers that have a minimal pressure loss on the loW pressure side are useful for systems using R507A, R134a, R12, R404A, R290, R407C, R600, and R410A. The liquid-suction heat exchanger is detrimental to system performance in systems using R22, R32, and R717.IntroductionLiquid-suction heat exchangers are commonly installed in refrigeration systems With the intent of ensuring proper system operation and increasing system performance.Specifically, ASHRAE(1998) states that liquid-suction heat exchangers are effective in:1) increasing the system performance2) subcooling liquid refrigerant to prevent flash gas formation at inlets to expansion devices3) fully evaporating any residual liquid that may remain in the liquid-suction prior to reaching the compressor(s)Figure 1 illustrates a simple direct-expansion vapor compression refrigeration system utilizing a liquid-suction heat exchanger. In this configuration, high temperature liquid leaving the heat rejection device (an evaporative condenser in this case) is subcooled prior to being throttled to the evaporator pressure by an expansion device such as a thermostatic expansion valve. The sink for subcoolingthe liquid is loW temperature refrigerant vapor leaving the evaporator. Thus, the liquid-suction heat exchanger is an indirect liquid-to-vapor heat transfer device. The vapor-side of the heat exchanger (betWeen the evaporator outlet and the compressor suction) is often configured to serve as an accumulator thereby further minimizing the risk of liquid refrigerant carrying-over to the compressor suction. In cases Where the evaporator alloWs liquid carry-over, the accumulator portion of the heat exchanger Will trap and, over time, vaporize the liquid carryover by absorbing heat during the process of subcooling high-side liquid.BackgroundStoecker and Walukas (1981) focused on the influence of liquid-suction heat exchangers in both single temperature evaporator and dual temperature evaporator systems utilizing refrigerant mixtures. Their analysis indicated that liquid-suction heat exchangers yielded greater performance improvements When nonazeotropic mixtures Were used compared With systems utilizing single component refrigerants or azeoptropic mixtures. McLinden (1990) used the principle of corresponding states to evaluate the anticipated effects of neW refrigerants. He shoWed that the performance of a system using a liquid-suction heat exchanger increases as the ideal gas specific heat (related to the molecular complexity of the refrigerant) increases. Domanski and Didion (1993) evaluated the performance of nine alternatives to R22 including the impact of liquid-suction heat exchangers. Domanski et al. (1994) later extended the analysis by evaluating the influence of liquid-suction heat exchangers installed in vapor compression refrigeration systems considering 29 different refrigerants in a theoretical analysis. Bivens et al. (1994) evaluated a proposed mixture to substitute for R22 in air conditioners and heat pumps. Their analysis indicated a 6-7% improvement for the alternative refrigerant system When system modifications included a liquid-suction heat exchanger and counterfloW system heat exchangers (evaporator and condenser). Bittle et al. (1995a) conducted an experimental evaluation of a liquid-suction heat exchanger applied in a domestic refrigerator using R152a. The authors compared the system performance With that of a traditional R12-based system. Bittle et al. (1995b) also compared the ASHRAE method for predicting capillary tube performance (including the effects of liquid-suction heat exchangers) With experimental data. Predicted capillary tube mass floW rates Were Within 10% of predicted values and subcooling levels Were Within 1.7 C (3F) of actual measurements.This paper analyzes the liquid-suction heat exchanger to quantify its impact on system capacity and performance (expressed in terms of a system coefficient of performance, COP). The influence of liquid-suction heat exchanger size over a range of operating conditions (evaporating and condensing) is illustrated and quantified using a number of alternative refrigerants. Refrigerants included in the present analysis are R507A, R404A, R600, R290,R134a, R407C, R410A, R12, R22, R32, and R717. This paper extends the results presented in previous studies in that it considers neW refrigerants, it specifically considers the effects of the pressure drops,and it presents general relations for estimating the effect of liquid-suction heat exchangers for any refrigerant.Heat Exchanger EffectivenessThe ability of a liquid-suction heat exchanger to transfer energy from the Warm liquid to the cool vapor at steady-state conditions is dependent on the size and configuration of the heat transfer device. The liquid-suction heat exchanger performance, expressed in terms of an effectiveness, is a parameter in the analysis. The effectiveness of the liquid-suction heat exchanger is defined in equation (1):Where the numeric subscripted temperature (T) values correspond to locations depicted in Figure 1. The effectiveness is the ratio of the actual to maximum possible heat transfer rates. It is related to the surface area of the heat exchanger. A zero surface area represents a system Without a liquid-suction heat exchanger Whereas a system having an infinite heat exchanger area corresponds to an effectiveness of unity.The liquid-suction heat exchanger effects the performance of a refrigeration system by in fluencing both the high and loW pressure sides of a system. Figure 2 shoWs the key state points for a vapor compression cycle utilizing an idealized liquid-suction heat exchanger on a pressure-enthalpy diagram. The enthalpy of the refrigerant leaving the condenser (state 3) is decreased prior to entering the expansion device (state 4) by rejecting energy to the vapor refrigerant leaving the evaporator (state 1) prior to entering the compressor (state 2). Pressure losses are not shoWn. The cooling of the condensate that occurs on the high pressure side serves to increase the refrigeration capacity and reduce the likelihood of liquid refrigerant flashing prior to reaching the expansion device. On the loW pressure side, the liquid-suction heat exchanger increases the temperature of the vapor entering the compressor and reduces the refrigerant pressure, both of Which increase the specific volume of the refr igerant and thereby decrease the mass floW rate and capacity. A major benefit of the liquid-suction heat exchanger is that it reduces the possibility of liquid carry-over from the evaporator Which could harm the compressor. Liquid carryover can be readily caused by a number of factors that may include Wide fluctuations in evaporator load and poorly maintained expansiondevices (especially problematic for thermostatic expansion valves used in ammonia service).（翻译）冷却系统利用流体吸热交换器克来因教授,布兰顿教授, , 布朗教授威斯康辛州的大学–麦迪逊摘录加热装置在许多冷却系统中被用到，用以制冷时遗留在蒸发器中的冷却气体和离开冷凝器发热流体之间的能量的热交换.这些流体吸收或吸收热交换器,在一些情形中，他们降低了系统性能, 然而系统的某些地方却得到了改善. 虽然以前研究员已经调查了流体吸热交换器的性能, 但是这项研究可能从早先研究的三种方式被加以区别. 首先，这份研究开辟了一个无限的崭新的与流体吸热交换器有关联的群体.其次，这份研究拓宽了早先的分析包括新型制冷剂。
暖通空调专业 毕业设计外文翻译3
外文翻译（1）Refrigeration System Performance using Liquid-Suction Heat ExchangersS. A. Klein, D. T. Reindl, and K. BroWnellCollege of EngineeringUniversity of Wisconsin - MadisonAbstractHeat transfer devices are provided in many refrigeration systems to e xchange energy betWeen the cool gaseous refrigerant leaving the evaporator and Warm liquid refrigerant exiting the condenser. These liquid-suction or suction-line heat exchangers can, in some cases, yield improved system performance While in other cases they degrade system performance. Although previous researchers have investigated performance of liquid-suction heat exchangers, this study can be distinguished from the previous studies in three Ways. First, this paper identifies a neW dimensionless group to correlate performance impacts attributable to liquid-suction heat exchangers. Second, the paper extends previous analyses to include neW refrigerants. Third, the analysis includes the impact of pressure drops through the liquid-suction heat exchanger on system performance. It is shoWn that reliance on simplified analysis techniques can lead to inaccurate conclusions regarding the impact of liquid-suction heat exchangers on refrigeration system performance. From detailed analyses, it can be concluded that liquid-suction heat exchangers that have a minimal pressure loss on the loW pressure side are useful for systems using R507A, R134a, R12, R404A, R290, R407C, R600, and R410A. The liquid-suction heat exchanger is detrimental to system performance in systems using R22, R32, and R717.IntroductionLiquid-suction heat exchangers are commonly installed in refrigeration systems With the intent of ensuring proper system operation and increasing system performance.Specifically, ASHRAE(1998) states that liquid-suction heat exchangers are effective in:1) increasing the system performance2) subcooling liquid refrigerant to prevent flash gas formation at inlets to expansion devices3) fully evaporating any residual liquid that may remain in the liquid-suction prior to reaching the compressor(s)Figure 1 illustrates a simple direct-expansion vapor compression refrigeration system utilizing a liquid-suction heat exchanger. In this configuration, high temperature liquid leaving the heat rejection device (an evaporative con denser in this case) is subcooled prior to being throttled to the evaporator pressure by an expansion device such as a thermostatic expansion valve. The sink for subcoolingthe liquid is loW temperature refrigerant vapor leaving the evaporator. Thus, the liquid-suction heat exchanger is an indirect liquid-to-vapor heat transfer device. The vapor-side of the heat exchanger (betWeen the evaporator outlet and the compressor suction) is often configured to serve as an accumulator thereby further minimizing the risk of liquid refrigerant carrying-over to the compressor suction. In cases Where the evaporator alloWs liquid carry-over, the accumulator portion of the heat exchanger Will trap and, over time, vaporize the liquid carryover by absorbing heat during the process of subcooling high-side liquid.BackgroundStoecker and Walukas (1981) focused on the influence of liquid-suction heat exchangers in both single temperature evaporator and dual temperature evaporator systems utilizing refrigerant mixtures. Their analysis indicated that liquid-suction heat exchangers yielded greater performance improvements When nonazeotropic mixtures Were used compared With systems utilizing single component refrigerants or azeoptropic mixtures. McLinden (1990) used the principle of corresponding states to evaluate the anticipated effects of neW refrigerants. He shoWed that the performance of a system using a liquid-suction heat exchanger increases as the ideal gas specific heat (related to the molecular complexity of the refrigerant) increases. Domanski and Didion (1993) evaluated the performance of nine alternatives to R22 including the impact of liquid-suction heat exchangers. Domanski et al. (1994) later extended the analysis by evaluating the influence of liquid-suction heat exchangers installed in vapor compression refrigeration systems considering 29 different refrigerants in a theoretical analysis. Bivens et al. (1994) evaluated a proposed mixture to substitute for R22 in air conditioners and heat pumps. Their analysis indicated a 6-7% improvement for the alternative refrigerant system When system modifications included a liquid-suction heat exchanger and counterfloW system heat exchangers (evaporator and condenser). Bittle et al. (1995a) conducted an experimental evaluation of a liquid-suction heat exchanger applied in a domestic refrigerator using R152a. The authors compared the system performance With that of a traditional R12-based system. Bittle et al. (1995b) also compared the ASHRAE method for predicting capillary tube performance (including the effects of liquid-suction heat exchangers) With experimental data. Predicted capillary tube mass floW rates Were Within 10% of predicted values and subcooling levels Were Within 1.7 C (3F) of actual measurements.This paper analyzes the liquid-suction heat exchanger to quantify its impact on system capacity and performance (expressed in terms of a system coefficient of performance, COP). The influence of liquid-suction heat exchanger size over a range of operating conditions (evaporating and condensing) is illustrated and quantified using a number of alternative refrigerants. Refrigerants included in the present analysis are R507A, R404A, R600, R290,R134a, R407C, R410A, R12, R22, R32, and R717. This paper extends the results presented in previous studies in that it considers neW refrigerants, it specifically considers the effects of the pressure drops,and it presents general relations for estimating the effect of liquid-suction heat exchangers for any refrigerant.Heat Exchanger EffectivenessThe ability of a liquid-suction heat exchanger to transfer energy from the Warm liquid to the cool vapor at steady-state conditions is dependent on the size and configuration of the heat transfer device. The liquid-suction heat exchanger performance, expressed in terms of an effectiveness, is a parameter in the analysis. The effectiveness of the liquid-suction heat exchanger is defined in equation (1):Where the numeric subscripted temperature (T) values correspond to locations depicted in Figure 1. The effectiveness is the ratio of the actual to maximum possible heat transfer rates. It is related to the surface area of the heat exchanger. A zero surface area represents a system Without a liquid-suction heat exchanger Whereas a system having an infinite heat exchanger area corresponds to an effectiveness of unity.The liquid-suction heat exchanger effects the performance of a refrigeration system by in fluencing both the high and loW pressure sides of a system. Figure 2 shoWs the key state points for a vapor compression cycle utilizing an idealized liquid-suction heat exchanger on a pressure-enthalpy diagram. The enthalpy of the refrigerant leaving the condenser (state 3) is decreased prior to entering the expansion device (state 4) by rejecting energy to the vapor refrigerant leaving the evaporator (state 1) prior to entering the compressor (state 2). Pressure losses are not shoWn. The cooling of the condensate that occurs on the high pressure side serves to increase the refrigeration capacity and reduce the likelihood of liquid refrigerant flashing prior to reaching the expansion device. On the loW pressure side, the liquid-suction heat exchanger increases the temperature of the vapor entering the compressor and reduces the refrigerant pressure, both of Which increase the specific volume of the refr igerant and thereby decrease the mass floW rate and capacity. A major benefit of the liquid-suction heat exchanger is that it reduces the possibility of liquid carry-over from the evaporator Which could harm the compressor. Liquid carryover can be readily caused by a number of factors that may include Wide fluctuations in evaporator load and poorly maintained expansiondevices (especially problematic for thermostatic expansion valves used in ammonia service).（翻译）冷却系统利用流体吸热交换器克来因教授,布兰顿教授, , 布朗教授威斯康辛州的大学–麦迪逊摘录加热装置在许多冷却系统中被用到，用以制冷时遗留在蒸发器中的冷却气体和离开冷凝器发热流体之间的能量的热交换.这些流体吸收或吸收热交换器,在一些情形中，他们降低了系统性能, 然而系统的某些地方却得到了改善. 虽然以前研究员已经调查了流体吸热交换器的性能, 但是这项研究可能从早先研究的三种方式被加以区别. 首先，这份研究开辟了一个无限的崭新的与流体吸热交换器有关联的群体.其次，这份研究拓宽了早先的分析包括新型制冷剂。
冷水机组 毕业设计外文翻译
英文翻译Chilled Water Systems[1]Chilled water systems were used in less than 4% of commercial buildings in the U.S. in 1995. However, because chillers are usually installed in larger buildings, chillers cooled over 28% of the U.S. commercial building floor space that same year (DOE, 1998). Five types of chillers are commonly applied to commercial buildings: reciprocating, screw, scroll, centrifugal, and absorption. The first four utilize the vapor compression cycle to produce chilled water. They differ primarily in the type of compressor used. Absorption chillers utilize thermal energy (typically steam or combustion source) in an absorption cycle with either an ammonia-water or water-lithium bromide solution to produce chilled water.Overall SystemFigure 4.2.2 shows a simple representation of a dual chiller application with all the major auxiliary equipment. An estimated 86% of chillers are applied in multiple chiller arrangements like that shown in the figure (Bitondo and Tozzi, 1999). In chilled water systems, return water from the building is circulated through each chiller evaporator where it is cooled to an acceptable temperature (typically 4 to 7°C) (39 to 45°F). The chilled water is then distributed to water-to-air heat exchangers spread throughout the facility. In these heat exchangers, air is cooled and dehumidified by the cold water. During the process, the chilled water increases in temperature and must be returned to the chiller(s).The chillers shown in Figure 4.2.2 are water-cooled chillers. Water is circulated through the condenser of each chiller where it absorbs heat energy rejected from the high pressure refrigerant. The water is then pumped to a cooling tower where the water is cooled through an evaporation process. Cooling towers are described in a later section. Chillers can also be air cooled. In this configuration, the condenserwould be a refrigerant-to-air heat exchanger with air absorbing the heat energy rejected by the high pressure refrigerant.Chillers nominally range in capacities from 30 to 18,000 kW (8 to 5100 ton). Most chillers sold in the U.S. are electric and utilize vapor compression refrigeration to produce chilled water. Compressors for these systems are either reciprocating, screw, scroll, or centrifugal in design. A small number of centrifugal chillers are sold that use either an internal combustion engine or steam drive instead of an electric motor to drive the compressor.[1]节选自James B. Bradford et al. “HVAC Equipment and Systems”.Handbook of Heating, Ventilation, and Air-Conditioning.Ed. Jan F. Kreider.Boca Raton, CRC Press LLC. 2001FIGURE 4.2.2 A dual chiller application with major auxiliary systems (courtesy of Carrier Corporation).The type of chiller used in a building depends on the application. For large office buildings or in chiller plants serving multiple buildings, centrifugal compressors are often used. In applications under 1000 kW (280 tons) cooling capacities, reciprocating or screw chillers may be more appropriate. In smaller applications, below 100 kW (30 tons), reciprocating or scroll chillers are typically used.Vapor Compression ChillersTable 4.2.5 shows the nominal capacity ranges for the four types of electrically driven vapor compression chillers. Each chiller derives its name from the type of compressor used in the chiller. The systems range in capacities from the smallest scroll (30 kW; 8 tons) to the largest centrifugal (18,000 kW; 5000 tons).Chillers can utilize either an HCFC (R-22 andR-123) or HFC (R-134a) refrigerant. The steady state efficiency of chillers is often stated as a ratio of the power input (in kW) to the chilling capacity (in tons). A capacity rating of one ton is equal to 3.52 kW or 12,000 btu/h. With this measure of efficiency, the smaller number is better. As seen in Table 4.2.5, centrifugal chillers are the most efficient; whereas, reciprocating chillers have the worst efficiency of the four types. The efficiency numbers provided in the table are the steady state full-load efficiency determined in accordance to ASHRAE Standard 30 (ASHRAE, 1995). These efficiency numbers do not include the auxiliary equipment, such as pumps and cooling tower fans that can add from 0.06 to 0.31 kW/ton to the numbers shown (Smit et al., 1996).Chillers run at part load capacity most of the time. Only during the highest thermal loadsin the building will a chiller operate near its rated capacity. As a consequence, it is important to know how the efficiency of the chiller varies with part load capacity. Figure 4.2.3 shows a representative data for the efficiency (in kW/ton) as a function of percentage full load capacity for a reciprocating, screw, and scroll chiller plus a centrifugal chiller with inlet vane control and one with variable frequency drive (VFD) for the compressor. The reciprocating chiller increases in efficiency as it operates at a smaller percentage of full load. In contrast, the efficiency of a centrifugal with inlet vane control is relatively constant until theload falls to about 60% of its rated capacity and its kW/ton increases to almost twice its fully loaded value.FIGURE 4.2.3 Chiller efficiency as a function of percentage of full load capacity.In 1998, the Air Conditioning and Refrigeration Institute (ARI) developed a new standard that incorporates into their ratings part load performance of chillers (ARI 1998c). Part load efficiency is expressed by a single number called the integrated part load value (IPLV). The IPLV takes data similar to that in Figure 4.2.3 and weights it at the 25%, 50%,75%, and 100% loads to produce a single integrated efficiency number. The weighting factors at these loads are 0.12, 0.45, 0.42, and 0.01, respectively. The equation to determine IPLV is:Most of the IPLV is determined by the efficiency at the 50% and 75% part load values. Manufacturers will provide, on request, IPLVs as well as part load efficiencies such as those shown in Figure 4.2.3.FIGURE 4.2.4 Volume-pressure relationships for a reciprocating compressor.The four compressors used in vapor compression chillers are each briefly described below. While centrifugal and screw compressors are primarily used in chiller applications, reciprocating and scroll compressors are also used in smaller unitary packaged air conditioners and heat pumps.Reciprocating CompressorsThe reciprocating compressor is a positive displacement compressor. On the intake stroke of the piston, a fixed amount of gas is pulled into the cylinder. On the compressionstroke, the gas is compressed until the discharge valve opens. The quantity of gas compressed on each stroke is equal to the displacement of the cylinder. Compressors used in chillers have multiple cylinders, depending on the capacity of the compressor. Reciprocating compressors use refrigerants with low specific volumes and relatively high pressures. Most reciprocating chillers used in building applications currently employ R-22.Modern high-speed reciprocating compressors are generally limited to a pressure ratio of approximately nine. The reciprocating compressor is basically a constant-volumevariable-head machine. It handles variousdischarge pressures with relatively small changes in inlet-volume flow rate as shown by the heavy line (labeled 16 cylinders) in Figure 4.2.4. Condenser operation in many chillers is related to ambient conditions, for example, through cooling towers, so that on cooler days the condenser pressure can be reduced. When the air conditioning load is lowered, less refrigerant circulation is required. The resulting load characteristic is represented by the solid line that runs from the upper right to lower left of Figure 4.2.4.The compressor must be capable of matching the pressure and flow requirements imposed by the system. The reciprocating compressor matches the imposed discharge pressure at any level up to its limiting pressure ratio. Varying capacity requirements can be met by providing devices that unloadindividual or multiple cylinders. This unloading is accomplished by blocking the suction or discharge valves that open either manually or automatically. Capacity can also be controlled through the use of variable speed or multi-speed motors. When capacity control is implemented on a compressor, other factors at part-load conditions need to considered, such as (a) effect on compressor vibration and sound when unloaders are used, (b) the need for good oil return because of lower refrigerant velocities, and (c) proper functioning of expansion devices at the lower capacities.With most reciprocating compressors, oil is pumped into the refrigeration system from the compressor during normal operation. Systems must be designed carefully to return oil to the compressor crankcase to provide for continuous lubrication and also to avoid contaminating heat-exchanger surfaces.Reciprocating compressors usually are arranged to start unloaded so that normal torque motors are adequate for starting. When gas engines are used for reciprocating compressor drives, careful matching of the torque requirements of the compressor and engine must be considered.FIGURE 4.2.5 Illustration of a twin-screw compressor design (courtesy of CarrierCorporation).Screw CompressorsScrew compressors, first introduced in 1958 (Thevenot, 1979), are positive displacement compressors. They are available in the capacity ranges that overlap with reciprocating compressors and small centrifugal compressors. Both twin-screw and single-screw compressors are used in chillers. The twin-screw compressor is also called the helical rotary compressor. Figure 4.2.5 shows a cutaway of a twin-screw compressor design. There are two main rotors (screws). One is designated male (4 in the figure) and the other female (6 in the figure).The compression process is accomplished by reducing the volume of the refrigerant with the rotary motion of screws. At the low pressure side of the compressor, a void is created when the rotors begin to unmesh. Low pressure gas is drawn into the void between the rotors. As the rotors continue to turn, the gas is progressively compressed as it moves toward the discharge port. Once reaching a predetermined volume ratio, the discharge port is uncovered and the gas is discharged into the high pressure side of the system. At a rotation speed of 3600 rpm, a screw compressor has over 14,000 discharges per minute (ASHRAE, 1996).Fixed suction and discharge ports are used with screw compressors instead of valves, as used in reciprocating compressors. These set the built-in volume ratio — the ratio of the volume of fluid space in the meshing rotors at the beginning of the compression process to the volume in the rotors as the discharge port is first exposed. Associated with the built-in volume ratio is a pressure ratio that depends on the properties of the refrigerant being compressed. Screw compressors have the capability to operate at pressure ratios of above 20:1 (ASHRAE, 1996). Peak efficiency is obtained if the discharge pressure imposed by the system matchesthe pressure developed by the rotors when the discharge port is exposed. If the interlobe pressure in the screws is greater or less than discharge pressure, energy losses occur but no harm is done to the compressor.Capacity modulation is accomplished by slide valves that provide a variable suction bypass or delayed suction port closing, reducing the volume of refrigerant compressed. Continuously variable capacity control is most common, but stepped capacity control is offered in some manufacturers’ machines. Variable discharge porting is available on some machines to allow control of the built-in volume ratio during operation.Oil is used in screw compressors to seal the extensive clearance spaces between the rotors, to cool the machines, to provide lubrication, and to serve as hydraulic fluid for the capacity controls. An oil separator is required for the compressor discharge flow to remove the oil from the high-pressure refrigerant so that performance of system heat exchangers will not be penalized and the oil can be returned for reinjection in the compressor.Screw compressors can be direct driven at two-pole motor speeds (50 or 60 Hz). Their rotary motion makes these machines smooth running and quiet. Reliability is high when the machines are applied properly. Screw compressors are compact so they can be changed out readily for replacement or maintenance. The efficiency of the best screw compressors matches or exceeds that of the best reciprocating compressors at full load. High isentropic and volumetric efficiencies can be achieved with screw compressors because there are no suction or discharge valves and small clearance volumes. Screw compressors for building applications generally use either R-134a or R-22.译文冷水机组1995年，在美国，冷水机组应用在至少4％的商用建筑中。
空调专业毕业设计外文翻译--工程热力学和制冷循环
附录B 英文翻译THERMODYNAMICS AND REFRIGERATION CYCLES THERMODYNAMICS is the study of energy, its transformations, and its relation to states of matter. This chapter covers the application of thermodynamics to refrigeration cycles. The first part reviews the first and second laws of thermodynamics and presents methods for calculating thermodynamic properties. The second and third parts address compression and absorption refrigeration cycles, two common methods of thermal energy transfer.THERMODYNAMICSA thermodynamic system is a region in space or a quantity of matter bounded by a closed surface. The surroundings include everything external to the system, and the system is separated from the surroundings by the system boundaries. These boundaries can be movable or fixed, real or imaginary. Entropy and energy are important in any thermodynamic system. Entropy measures the molecular disorder of a system. The more mixed a system, the greater its entropy; an orderly or unmixed configuration is one of low entropy. Energy has the capacity for producing an effect and can be categorized into either stored or transient forms.Stored EnergyThermal (internal) energy is caused by the motion of molecules and/or intermolecular forces.Potential energy (PE) is caused by attractive forces existing between molecules, or the elevation of the system.mgzPE=(1)wherem =massg = local acceleration of gravityz = elevation above horizontal reference planeKinetic energy (KE) is the energy caused by the velocity of molecules and is expressed as22m VKE=(2)whereV is the velocity of a fluid stream crossing the system boundary.Chemical energy is caused by the arrangement of atoms composing the molecules.Nuclear (atomic) energy derives from the cohesive forces holding protons and neutrons together as the atom’s nucleus.Energy in TransitionHeat Q is the mechanism that transfers energy across the boundaries of systems with differing temperatures, always toward the lower temperature. Heat is positive when energy is added to the system (see Figure 1).Work is the mechanism that transfers energy across the boundaries of systems with differing pressures (or force of any kind),always toward the lower pressure. If the total effect produced in the system can be reduced to the raising of a weight, then nothing but work has crossed the boundary. Workis positive when energy is removed from the system (see Figure 1).Mechanical or shaft work W is the energy delivered or absorbed by a mechanism, such as a turbine, air compressor, or internal combustion engine.Flow work is energy carried into or transmitted across the system boundary because a pumping process occurs somewhere outside the system, causing fluid to enter the system. It can bemore easily understood as the work done by the fluid just outside the system on the adjacent fluid entering the system to force or push it into the system. Flow work also occurs as fluid leaves the system.Flow work =pv (3)where p is the pressure and v is the specific volume, or the volume displaced per unit mass evaluated at the inlet or exit.A property of a system is any observable characteristic of the system. The state of a system is defined by specifying the minimum set of independent properties. The most common thermodynamic properties are temperature T, pressure p, and specific volume v or density ρ. Additional thermodynamic properties include entropy, stored forms of energy, and enthalpy.Frequently, thermodynamic properties combine to form other properties. Enthalpy h is an important property that includes internal energy and flow work and is defined as≡(4) pvh+uwhere u is the internal energy per unit mass.Each property in a given state has only one definite value, and any property always has the same value for a given state, regardless of how the substance arrived at that state.A process is a change in state that can be defined as any change in the properties of a system. A process is described by specifying the initial and final equilibrium states, the path (if identifiable), and the interactions that take place across system boundaries during theprocess.A cycle is a process or a series of processes wherein the initial and final states of the system are identical. Therefore, at the conclusion of a cycle, all the properties have the same value they had at the beginning. Refrigerant circulating in a closed system undergoes acycle.A pure substance has a homogeneous and invariable chemical composition. It can exist in more than one phase, but the chemical composition is the same in all phases.If a substance is liquid at the saturation temperature and pressure,it is called a saturated liquid. If the temperature of the liquid is lower than the saturation temperature for the existing pressure, it is called either a subcooled liquid (the temperature is lower than the saturation temperature for the given pressure) or a compressed liquid (the pressure is greater than the saturation pressure for the given temperature).When a substance exists as part liquid and part vapor at the saturation temperature, its quality is defined as the ratio of the mass of vapor to the total mass. Quality has meaning only when the substance is saturated (i.e., at saturation pressure and temperature).Pressure and temperature of saturated substances are not independent properties.If a substance exists as a vapor at saturation temperature and pressure, it is called a saturated vapor. (Sometimes the term dry saturated vapor is used to emphasize that the quality is 100%.)When the vapor is at a temperature greater than the saturation temperature, it is a superheated vapor. Pressure and temperature of a superheated vapor are independent properties, because the temperature can increase while pressure remains constant. Gases such as air at room temperature and pressure are highly superheated vapors.FIRST LAW OF THERMODYNAMICSThe first law of thermodynamics is often called the law of conservation of energy. The following form of the first-law equation is valid only in the absence of a nuclear or chemical reaction.Based on the first law or the law of conservation of energy for any system, open or closed, there is an energy balance asNet amount of energy Net increase of stored=added to system energy in systemor[Energy in] – [Energy out] = [Increase of stored energy in system]Figure 1 illustrates energy flows into and out of a thermodynamic system. For the general case of multiple mass flows with uniform properties in and out of the system, the energy balance can be written=-++++-+++∑∑W Q gz V pv u m gz V pv u m out out in in )2()2(22 []system i i f f gz V pv u m gz V pv u m )2()2(22++-++ (5)where subscripts i and f refer to the initial and final states,respectively.Nearly all important engineering processes are commonly modeled as steady-flow processes. Steady flow signifies that all quantities associated with the system do not vary with time. Consequently,0)2()2(22=-+++-++∑∑W Q gz V h m gz V h m leavingstream all entering stream all (6)where h = u + pv as described in Equation (4).A second common application is the closed stationary system for which the first law equation reduces to[]system i f u u m W Q )(-=- (7)SECOND LAW OF THERMODYNAMICSThe second law of thermodynamics differentiates and quantifies processes that only proceed in a certain direction (irreversible) from those that are reversible. The second law may be described in several ways. One method uses the concept of entropy flow in an open system and the irreversibility associated with the process. The concept of irreversibility provides added insight into the operation of cycles. For example, the larger the irreversibility in a refrigeration cycle operating with a given refrigeration load between two fixed temperature levels, the larger the amount of work required tooperate the cycle. Irreversibilities include pressure drops in lines andheat exchangers, heat transfer between fluids of different temperature, and mechanical friction. Reducing total irreversibility in a cycle improves cycle performance. In the limit of no irreversibilities, a cycle attains its maximum ideal efficiency. In an open system, the second law of thermodynamics can be described in terms of entropy asdI s m s m dS e e i i T Q system +-+=δδδ(8)wheredS = total change within system in time dt during process systemδm s = entropy increase caused by mass entering (incoming)δm s = entropy decrease caused by mass leaving (exiting)δQ/T = entropy change caused by reversible heat transfer between system and surroundings at temperature TdI = entropy caused by irreversibilities (always positive)Equation (8) accounts for all entropy changes in the system. Rearranged, this equation becomes []I d dS s m s m T Q sys i i e e -+-=)(δδδ (9)In integrated form, if inlet and outlet properties, mass flow, and interactions with the surroundings do not vary with time, the general equation for the second law isI ms ms T Q S S out in revsystem i f +-+=-∑∑⎰)()(/)(δ (10)In many applications, the process can be considered to operate steadily with no change in time. The change in entropy of the system is therefore zero. The irreversibility rate, which is the rate of entropy production caused by irreversibilities in the process, can be determined by rearranging Equation (10):∑∑∑--=surrin out T Q ms ms I )()( (11) Equation (6) can be used to replace the heat transfer quantity.Note that the absolute temperature of the surroundings with which the system is exchanging heat is used in the last term. If the temper-ature of the surroundings is equal to the system temperature, heat istransferred reversibly and the last term in Equation (11) equals zero.Equation (11) is commonly applied to a system with one mass flow in, the same mass flow out, no work, and negligible kinetic or potential energy flows. Combining Equations (6) and (11) yields []surr inout in out T h h s s m I ---=)( (12)In a cycle, the reduction of work produced by a power cycle (or the increase in work required by a refrigeration cycle) equals the absolute ambient temperature multiplied by the sum of irreversibilities in all processes in the cycle. Thus, the difference in reversible and actual work for any refrigeration cycle, theoretical or real, operating under the same conditions, becomes∑+=I T W W reversible actual 0 (13)THERMODYNAMIC ANAL YSIS OFREFRIGERATION CYCLESRefrigeration cycles transfer thermal energy from a region of low temperature T to one of higher temperature. Usually the higher-T R temperature heat sink is the ambient air or cooling water, at temperature T 0, the temperature of the surroundings.The first and second laws of thermodynamics can be applied to individual components to determine mass and energy balances and the irreversibility of the components. This procedure is illustrated in later sections in this chapter.Performance of a refrigeration cycle is usually described by a coefficient of performance (COP), defined as the benefit of the cycle (amount of heat removed) divided by the required energy input to operate the cycle:Useful refrigerating effectCOP ≡Useful refrigeration effect/Net energy supplied from external sources (14)Net energy supplied from external sources For a mechanical vapor compression system, the net energy supplied is usually in the form of work, mechanical or electrical, and may include work to the compressor and fans or pumps. Thus,net evapW Q COP = (15)In an absorption refrigeration cycle, the net energy supplied is usually in the form of heat into the generator and work into the pumps and fans, ornet gen evapW Q Q COP += (16)In many cases, work supplied to an absorption system is very small compared to the amount of heat supplied to the generator, so the work term is often neglected.Applying the second law to an entire refrigeration cycle shows that a completely reversible cycle operating under the same conditions has the maximum possible COP. Departure of the actual cycle from an ideal reversible cycle is given by the refrigerating efficiency:tev R COP COP)(=η (17)The Carnot cycle usually serves as the ideal reversible refrigeration cycle. For multistage cycles, each stage is described by a reversible cycle.工程热力学和制冷循环工程热力学是研究能量及其转换和能量与物质状态之间的关系。
毕业设计蒸发式冷凝器
摘要本课程设计是关于蒸发式冷凝器的设计，针对蒸发式冷凝器的换热过程同时存在显热和潜热交换，计算过程比较复杂且方法较多的情况，采用一种简单的蒸发式冷凝器的设计计算方法，通过基本参数确定、盘管设计、水系统设计和风系统设计，进行系统设计计算，得出换热量、传热面积、淋水量、水泵功率和风机功率等设计参数，该方法适用于常规蒸发式冷凝器的设计计算。
关键词：蒸发式冷凝器；盘管；水系统；风系统。
AbstractThe evaporative condenser is designed. For the heat transfer process of evaporative condenser with latent heat exchange and sensible heat exchange, the calculation method is complex. It has a lot of method for evaporative condenser and a simple practical design calculation method of evaporative condenser is used for the design and calculations of the conventional evaporative condenser.Through the calculation of basic parameters, coil design, water system design and air system design, system design calculations were completed. The quantity of heat transfer, the area of heat transfer, the quantity of spray water, pump power and fan power were calculated. This method is applicable to the conventional design and calculation of the evaporative condenser.Keywords ：evaporative condenser; coil ; water system ; air system目录绪论 (1)第1章冷凝器的种类 (2)1.1水冷式冷凝器 (2)1.1.1立式壳管式冷凝器 (2)1.1.2卧式壳管式冷凝器 (3)1.1.3套管式冷凝器 (3)1.2空气冷却式冷凝器 (4)1.3淋水式式冷凝器 ................. 错误！未定义书签。
毕业设计_BJS1200浮头式冷凝器设计
2、本课题研究的主要内容： （1）完成冷凝器（管程设计压力为 2.5MPa，壳程设计压力为 1.0MPa,壳程介质 R113 即三氯三氟乙烷进出口温度 65ºC/40ºC，管程介质自来水进出口温度 18ºC/34ºC，公称 换热面积 610m2）整体结构及零部件设计计算。 （2）进行冷凝器的热力过程分析，完成换热器受压元件的强度计算，完成传热面 积及换热量的计算。 3、提交的成果： （1）毕业设计（论文）正文； （2）A1 图纸 1 张，A2 图纸 1 张，A3 图纸 1 张； （3）至少一篇引用的外文文献及其译文； （4）附不少于 10 篇主要参考文献的题录及摘要。
指导教师（签字） 教研室主任（签字） 批准日期 接受任务书日期
完成日期 接受任务书学生（签字）
BJS1200 浮头式冷凝器设计
摘要
换热器是国民经济和工业生产领域中应用十分广泛的热量交换设备。 随着现 代新 工艺、新技术、新材料的不断开发和能源问题的日趋严重，世界各国已普遍 把石油化 工深度加工和能源综合利用摆到十分重要的位置。换热器因而面临着新 的挑战。换热 器的性能对产品质量、能量利用率以及系统运行的经济性和可靠性 起着重要的作用， 有时甚至是决定性的作用。目前在发达的工业国家热回收率已 达 96%。换热设备在现 代装置中约占设备总重的 30%左右，其中管壳式换热器仍然占绝对的优势，约 70%。其 余 30%为各类高效紧凑式换热器、新型热管热泵和蓄热器等设备，其中板式、螺旋板式、 板翅式以及各类高效传热元件的发展十分迅速。 在继续提高设备热效率的同时，促进 换热设备的结构紧凑性，产品系列化、标准化和专业化，并朝大型化的方向发展。本设 计旨在本课题研究的主要内容： （1）完成冷凝器整体结构及零部件设计计算。 （2）进行传热面积及 换热量的计算。
毕业设计冷凝器[管理资料]
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本科毕业设计说明书乙烯塔回流过冷器改进设计ETHYLENE TOWER REFLUX COOLING DEVICE IMPROVEMENT DESIGN学院（部）：机械工程学院专业班级：过控学生姓名：vvvvv指导教师：vvvvvvvvv2012 年 6 月15 日乙烯塔回流过冷器改进设计摘要该设计为大庆石化60万吨/年乙烯装置设计乙烯塔回流过冷器。
作为石油化工基础性原料，乙烯是石油化工的“龙头”，其生产的乙烯、丙烯、丁二烯和芳烃是所有化工产品的最基础原料。
乙烯塔回流过冷器是一种换热器，通常采用釜式换热器，也是一种管壳式换热器。
在乙烯塔装置中占有较重要的地位，它直接影响产品的质量和产量。
本次设计的乙烯塔回流过冷器的型号为BKU。
由于设计温度极低，对材料的要求较高。
本次设计主要是根据给定的设计条件，依据GB150-1998《钢制压力容器》和GB151-1999《管壳式换热器》等标准，对换热器进行了结构和强度的设计。
关键词：过冷器，釜式重沸器，换热器，乙烯ETHYLENE TOWER REFLUX COOLING DEVICEIMPROVEMENT DESIGNABSTRACTThe design for the Daqing Petrochemical 600,000 tons / year ethylene plant ethylene tower reflux cooling device design As the basic petrochemical raw materials, petrochemical ethylene is "bibcock", its production of ethylene, propylene, butadiene and aromatic hydrocarbons are all the basic raw materials of chemical products.Ethylene tower reflux cooling device is a heat exchanger, usually in a kettle type heat exchanger, which is also a kind of shell and tube heat exchanger. It occupies an important position in the ethylene tower unit and directly affects the product quality and yield.The model of the ethylene tower reflux cooler designed is BKU.Because the design temperature is very low, the requirements of the material are high.The design is based on the given design conditions, basis of GB150-1998 steel pressure vessel and GB151-1999 shell and tube heat exchanger and other standards, the design of the structure and intensity of the heat exchanger.KEYWARDS：Supercooling apparatus,kettle-type reboiler, heat exchanger, ethylene目录摘要 (I)ABSTRACT (II)1绪论 (1)引言 (1)换热器的基本要求及选型时需要考虑的因素 (1)管壳式换热器的研究现状 (2)釜式重沸器 (3)2换热器材料选择 (3) (4)3 换热器主要部件设计 (4)换热管设计 (4) (4) (5) (5) (5) (6) (6) (6) (6) (7) (7) (7) (8) (8) (8)管板设计 (9) (9) (10) (13) (13) (14) (15) (15) (16) (17) (17) (18)接管法兰的选取 (19)垫片的选取 (21)紧固件的选用 (21)设备法兰设计 (22)法兰的选取 (22) (24) (24)支持板 (25)支持板的尺寸 (25) (26) (27)拉杆与定距管 (28)拉杆的结构形式 (28) (28)拉杆的尺寸 (28) (29)定距管尺寸 (29)滑道结构 (29)鞍座的选取 (30)5换热器的制造、检验、安装与维修 (30)、检验与验收 (30) (30) (31) (31) (31) (31) (31) (32) (32) (32) (32)总结 (33)参考文献 (34)致谢 (35)1绪论引言化工生产中，绝大多数的工艺过程都有加热、冷却、汽化和冷凝的过程，这些过程总称为传热过程。
毕业设计(论文)外文资料翻译-空冷热交换器和空冷塔[管理资料]
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（二 〇 〇 七 年 六 月本科毕业论文 外文翻译 题 目：空冷热交换器和空冷塔 学生姓名： 学 院：电力学院 系 别：能源与动力工程 专 业：热能与动力工程 班 级：动本2003② 指导教师：学校代码： 10128学 号： 031203060Air-cooled Heat Exchangers and Cooling Towers. (MIT)(This text is a part of MR KROGER's book. include , , )RECIRCULATIONHeated plume air may recirculate in an air-cooled heat exchanger, thereby reducingthe cooling effectiveness of the system. Figure depicts, schematically, a cross-section of an air-cooled heat exchanger. In the absence of wind, the buoyant jet or plume rises vertically above the heat exchanger. A part of the warm plume air may however be drawn back into the inlet of the tower. This phenomenon is known as "recirculation". Plume recirculation is usually a variable phenomenon influenced by many factors, including heat exchanger configuration and orientation, surrounding structures and prevailing weather conditions. Because of higher discharge velocities, recirculation is usually less in induced draft than in forced draft designs.Figure : Air-flow pattern about forced draft air-cooled heat exchanger.Lichtenstein [51LI1] defines a recirculation factor asm m m m m r r r a r /)/(=+= ()where mr is the recirculating air mass flow rate, while ma is the ambient air flow rateinto the heat exchanger.Although the results of numerous studies on recirculation do appear in the literature,most are experimental investigations performed on heat exchangers having specific geometries and operating under prescribed conditions . [74KE1, 81SL1]. Gunter and Shipes [72GUll define certain recirculation flow limits and present the results of field tests performed on air-cooled heat exchangers. Problems associated with solving recirculating flow patterns numerically have been reported [81EP1]. Kroger et al. investigated theproblem analytically, experimentally and numerically and recommend a specific equationwith which the performance effectiveness of essentially two-dimensional mechanical draftheat exchangers experiencing recirculation, can be predicted [88KR1, 89KR1, 91DU1,93DU1, 95DU1].RECIRCULATION ANALYSISConsider one half of a two-dimensional mechanical draft air-cooled heat exchanger inwhich recirculation occurs. For purposes of analysis, the heat exchanger is represented by astraight line at an elevation Hi above ground level as shown in figure (a).Figure : Flow pattern about heat exchanger.It is assumed that the velocity of the air entering the heat exchanger along itsperiphery is in the horizontal direction and has a mean value, vi (the actual inlet velocity ishighest at the edge of the fan platform and decreases towards ground level). The outletvelocity, vo, is assumed to be uniform and in the vertical direction.Consider the particular streamline at the outlet of the heat exchanger that divergesfrom the plume at 1 and forms the outer "boundary" of the recirculating air stream. Thisstreamline will enter the platform at 2, some distance Hr below the heat exchanger. Forpurposes of analysis it will be assumed that the elevation of 1 is approximately Hr abovethe heat exchanger. If viscous effects, mixing and heat transfer to the ambient air areneglected, Bernoulli's equation can be applied between 1 and 2 to give)(2/)(2/222211r i o o r i o o H H g v p H H g v p -++=+++ρρρρ ()It is reasonable to assume that the total pressure at I is approximately equal to thestagnation pressure of the ambient air at that elevation .12112/a o p v p =+ρ ()At2 the static pressure can be expressed as2/2222v p p a a ρ-= ()Furthermore, for the ambient air far from the heat exchanger212a r a a p gH p =+ρ ()Substitute equations (), () and () into equation () and findg v H r 4/22= ()Due to viscous effects the velocity at the inlet at elevation Hi is in practice equal tozero. The Velocity gradient in this immediate region is however very steep and the velocitypeaks at a value that is higher than the mean inlet velocity. Examples of numericallydetermined inlet velocity distributions for different outlet velocities and heat exchangergeometries are shown in figure [95DU1]. Since most of the recirculation occurs in thisregion the velocity v2 is of importance but difficult to quantify analytically. For 1)2/(≤i i H W it will be assumed that v2 can be replaced approximately by the mean inletvelocity, vi, in equation (). Thus g v H i r 4/2= () Figure : Two-dimensional inlet velocity distribution for Wi/2 = m.According to the equation of mass conservation, the flow per unit depth of the towercan be expressed as)2/(2/)(i a i o o i i o o i r i a i r o H W v v or W v v H H v H ρρρρρ≈=-+ ()if the amount of recirculation is small.According to equations () and () the recirculation factor isia r o i o o r i o r H H W v H v m m r ρρρρ===2 () Substitute equations () and () into equation () and findFr H W gW v H W r ia i o i o i a i o 323)(321)(161ρρρρ== () where )/(22i o gW v Fr =is the Froude number based on the width of the heatexchanger.The influence of a wind wall or deep plenum can be determined approximately by considering flow conditions between the top of the wind wall, (Hi + Hw), as shown in figure (b) and elevation Hi. Consider the extreme case when Hw is so large (Hw = Hwo) that no recirculation takes place and the ambient air velocity near the top of the wind wall is zero. In this particular case the static pressure at the tower exit is essentially equal to the ambient stagnation pressure. With these assumptions, apply Bernoulli's equation between the tower outlet at the top of the wind wall and the elevation Hi.2212/a wo o o o a p gH v p =++ρρ ()But wo a a a gH p p ρ=-12 () Substitute equation () into equation () and find])(2[2g v H o a o o wo ρρρ-= ()If it is assumed that the recirculation decreases approximately linearly with increasing wind wall height, equation (8,) may be extended as follows:)1()(3213wow i a i o H H a Fr H W r -=ρρ () Since the recirculation is assumed to be essentially zero at Hw = Hwo, find a = 1. Substitute equation () into equation () and find]21[)(321])(21[)(1613223w i a i o oo w o a i o i a i o FrD Fr H W v gH gW v H W r -=--=ρρρρρρρ () where ])/[(2w o a o o w gH v FrD ρρρ-= is the densimetric Froude number based on the wind wall height.It is important to determine the effectiveness of the system when recirculation occurs. Effectiveness in this case, is defined asQ Q e r r ==ion recirculat no fer with heat trans ion recirculat fer with heat trans () The interrelation between the recirculation and the effectiveness is complex in a real heat exchanger. Two extremes can however be evaluated analytically .1. No mixingThe warm recirculating air does not mix at all with the cold ambient inflow, resulting in a temperature distribution as shown in figure (a). The recirculating stream assumes thetemperature of the heat exchanger fluid he T .Figure : Recirculation flow patterns.This in effect means that the part of the heat exchanger where recirculation occurs, transfers no heat. The actual heat transfer rate is thus given by)(a o p a r T T c m Q -= ()resulting in an effectiveness due to recirculation ofr m m m T T c m m T T c m e r a o p r a a o p a r -=-=-+-=1)()()()( () Substitute equation () into equation () and find ])(21[)(1611223oo w o a i o i a i o r v gH gW v H W e ρρρρρ---= () 2. Perfect mixingThe recirculating air mixes perfectly with the inflowing ambient air, resulting in a uniform increase in both the effective inlet air temperature and the outlet air temperature as shown in figure (b).If for purpose of illustration, it is assumed that the temperature of the heatexchanger,he T ,is constant, it follows from equation () that the effectiveness under cross-flow conditions is)/exp(1)()()()(p ir he ir or ir he p ir or p mc UA T T T T T T mc T T mc e --=--=--= () or )/exp()(p ir he he or mc UA T T T T ---= () Furthermore the enthalpy entering the heat exchanger isor p r a p a ir p T c m T c m T mc += or or a or r a r ir rT T r mT m m T m m T +-=+-=)1()( () Substitute equation () into equation () and find)/exp(1)/exp(])1([)/exp(])1([p p a he he p or a he he or mc UA r mc UA T r T T mc UA rT T r T T T ------=-----=() In this case the effectiveness due to recircuiation is given byao ir or a o p ir or p r T T T T T T mc T T mc e --=--=)()( From equation () and (), substitute the values of Tir and Tor into this equation, to find the effectiveness of the heat exchanger.])/exp(1)/exp(})1({[)()1(a p p a he he ar or r T mc UA r ms UA T r T T T T r e ---------= () In practice the effectiveness will be some value between that given by equation () and equation (). Actual measurements conducted on air-cooled heat exchangers appear to suggest that relatively little mixing occurs. This tendency is confirmed by numerical analysis of the problem [89KR1, 95DU1].Figure : Heat exchanger effectiveness.Duvenhage and Kroger [95DU1] solved the recirculation problem numerically and correlated their results over a wide range of operating conditions and heat exchanger geometries by means of the following empirical equation:])/2()/2(006027.0[1755515.044641.01352.1D i w i i r Fr W H W H e ---= ()This equation is valid in the 79.0/2049.0,75.2/249.0≤≤≤≤i w i i W H W H and3.14175.0≤≤D Fr where ])/[(22i o a o a D gW v Fr ρρρ-=. In this equation w H represents the effective height above the inlet to the fan platform and includes the plenum height in addition to any wind wall height.Equation （) is shown graphically in figure . For values of 265.0/2Di i Fr W H ≥ ,equation () is in good agreement with equation(). MEASURING RECIRCULATIONIn the absence of wind walls, recirculation can be significant resulting in acorresponding reduction in heat transfer effectiveness. As shown in figure , smokegenerated at the lower end outlet of an A-frame type forced draft air-cooled heat exchanger without wind walls, is drawn directly downwards into the low pressure region created by the fans. The results of recirculation tests conducted at the Marimba power plant are reported by Conradie and Kroger [89CO1]. They actually measured the verticaltemperature distribution of the air entering the heat exchanger and observed a relatively higher temperature in the vicinity of the fan platform. As shown by the smoke trail in figure recirculation of the plume air occurs in this region Because of the approximately 10 m high wind wall surrounding the array of A-frame heat exchanger bundles, a reduction in effectiveness of less that one percent is experienced under normal operating conditions in the absence of wind. The effectiveness can be determined according to equation ().: Plume air recirculating in air-cooled steam condenser.: Visualization of recirculation with smoke at the Matimba power plant.Generally less recirculation occurs in induced draft cooling systems due to the relatively high fan outlet velocity and height of diffuser if one is present.There are numerous situations where a minimum tube wall temperature must be maintained. For example to avoid plugging during cooling of heavy crude stocks with high pour points or in the case where there is a danger of solidification fouling due to the deposition of ammonium salts when tube wall temperatures fall below 70~ C in an overhead condenser for a sour water stripper etc. air temperature control is essential. In such situations recirculation is employed in a system incorporating automatically controlled louvers that cause more or less of the hot plume air to mix with the ambient cooling air as shown in figure . Other arrangements are also possible [80RU1].Figure : Louver controlled plume air recirculation in air-cooled heat exchanger.Steam coils located immediately below the tube bundles may be required to preheat the air during startup in winter.OF WIND ON AIR-COOLED HEAT EXCIHANGERSIn general winds have a negative effect on the performance of mechanical draft heat exchangers. Plume air recirculation tends to increase while fan performance is usually reduced during windy periods.Laboratory studies and field tests have shown that the output of dry-cooled power stations may be significantly reduced by winds. As shown in figure the wind speed and direction significantly influences the turbine output at the Wydok power plant [76SC1].Figure : Reduction in turbine output due to wind at the Wyodak power plant.Before the 160 MWe power plant at Utrillas in Spain was built, extensive model tests (scale 1:150) were conducted to determine the optimum position of the air-cooled condenser and power plant orientation, taking into consideration local wind patterns. The results of the tests are shown in figure .Goldshagg [93GO1] reports that turbine performance at the Matimba power plant was reduced measurably during certain windy periods and that occasional turbine trips had occurred under extremely gusty conditions. After extensive experimental and numerical investigations modifications to the wind walls and cladding were implemented as shown in figure . Due to the resultant improved air flow pattern into the air-cooled condenser during periods of westerly winds, no further trips were experienced and performance was significantly improved [97GO1].Figure : Reduction in turbine output at the Utrillas power plant due to wind.Figure : Modifications at the Matimba power plant.From the case studies listed above it is clear that the interaction between the air cooled heat exchanger and adjacent buildings or structures can significantly complicate flow patterns and consequently reduce plant performance.Kennedy and Fordyce [74KE1] report the results of model studies to determine downwind temperature distribution, recirculation and interference (ingestion of an adjacent tower's effluent plume) characteristics.Slawson and Sullivan [81SL1] conducted experiments in a water plume to recirculation and interference for two conceptual configurations of forced draft dry-cooling towers, a rectangular array and a multiple round tower arrangement. The objective of the study was to investigate and make recommendations on the design and arrangement ofcooling towers in order to provide optimum ambient air distribution to the heat transfer surfaces. Optimum air distribution is maintained by minimizing recirculation and interference. Recirculation and interference measurements of 40 to 70 percent were found to exits for the rectangular array concept, while values of 20 to 30 percent were measured for the round tower arrangement.Field tests conducted by the Cooling Tower Institute (CTI) on induced mechanical draft cooling towers, clearly show a measurable increase of plume recirculation with an increase in wind speed when the wind blows in the longitudinal direction of the cooling, tower bank [58CT1,77CT1]. The results of numerous other experimental studies on recirculation have been reported [71GU1, 72GU1, 74KE1, 76ON1, 81SL1, 88t).11].In addition to the effect of recirculation, the performance of the funs, especially in forced draft systems, are influenced during windy periods due to inlet air flow distortions.Duvenhage and Krosger [96DU1] numerically modelled the air flow patterns about and through, an air-cooled heat exchanger during windy conditions, taking into consideration the coupled effects of both recirculation and fan performance. They consider a long heat exchanger bank as shown schematically in figure consisting of bays, each bay having two 6-blade m diameter fans. The heat exchanger is subjected to winds blowing across or parallel to the longitudinal axis and having a velocity distribution as given by equation () with b = as recommended by VDI 2049 [78VDI] .: Schematic of air cooled heat exchanger.Figure : Details of bay geometry.A more detailed cross-section of the bay is shown in figure . Each bay has an effective bundle frontal area of m x m - m2 and a tube bundle height of m. The fans have cylindrical inlet shrouds. The fan platform or inlet height Hi = m and the plenum chamber is 3 m high. They find that with increasing wind speed the air volume flow rate through the upwind fans (Fup) is reduced due to flow distortions while the flow through the downwind fans (Fdo) may actually increase slightly as shown ill figure , due to the increased kinetic energy in the air stream. The air-cooled heat exchanger performance is however reduced due to a net decrease in mean air volume flow rate through the fans (Fro) during windy periods.Figure : Fan air flow rate during crosswinds for an inlet height Hi = m.The influence on performance of recirculating hot plume air in this installation is relatively small. As shown in figure the effectiveness of the heat exchanger actually increases slightly for a light wind when compared to windless conditions. This is due to the fact that recirculation at the downwind side of the heat exchanger is eliminated. At higherwind speed recirculation gradually increases. This trend is in agreement with results observed by DU Toit et al. [93D153].To evaluate the influence of the inlet height on air flow rate through the particular heat exchanger, Hi was varied in the numerical model while a fixed wind profile was retained with a reference velocity of Vwr - 3 m/s at a reference height of zr = m. The corresponding changes in fan air volume flow rate and effectiveness are shown in figures and respectively. By increasing the height of the fan platform, the performance of the heat exchanger is improved due to the corresponding increasing air flow rate. The change in recirculation is small.Figure : Effectiveness due to recirculation during crosswinds for an inlet height Hi= .Figure : Fan air flow rate during crosswind for different fan platform heights.Figure : Effectiveness due to recirculation during crosswinds for different fan platform height.Figure : Recirculation for winds blowing in the direction of the longitudinal axis.The influence on performance of winds blowing in the direction of the longitudinal axis are evaluated numerical/y for a fan platform height of m with wind reference velocities of 3 m/s and 5 m/s at a reference height of m Heat exchanger banks consisting of up to 6 bays are evaluated. In the numerical model the crosswind solutions are applied to the two fans in the first two up-wind bays while the remaining fans are assumed to operate ideally. The resultant recirculation is shown in figure . The corresponding heat exchanger effectiveness is given by er = I - r.Recirculation clearly increases with increasing heat exchanger length and wind speed. For purposes of comparing trends, a correlation for recirculation recommended by the CTI [58CT1, 77CT1] is also shown in figure . It should be noted that this correlation isapplicable to induced draft cooling towers although the authors do state that they expect the recirculation of a forced draft system to be double the value of the correlation shown. Duvenhage et al. [96DU2] show that the addition of a solid walkway along the periphery of the air-cooled heat exchanger (at the fan platform elevation) tends to improve the mean flow rate through the fans (see figure ).Figure : Walkway effectAccording to the abovementioned findings the reduction of performance in a long forced draft air-cooled heat exchanger may generally be ascribed primarily to a reduction in air flow through the fans along the windward side of the bank when crosswinds prevail as shown in figure (a), and to recirculation of hot plume air as shown in figure (b) when the winds blow in the direction of the major axis of the heat exchanger. Fahlsing [95FAll observed reverse rotation of out of service fans on the windward side of a large air-cooled condenser when crosswinds prevailed.Figure : Flow patterns reducing performance. RECIRCULATION AND INTERFERENCEAs in the case of banks of air-cooled heat exchangers，recirculation of hot，moist plume air is known reduce the performance of rows of cooling tower units or cells [77CI1，88BS1].Furthermore, when several banks of air-cooled heat exchangers or rows of cooling tower cell are located next to each other，the plume of one bank or row may be drawn into an adjacent one．This phenomenon is referred to as interference.Ribier [88RI1] conducted recirculation tests on models of induced draft cooling towers cells similar to the types shown in figure , but without a diffuser. Initial tests were conducted on a row consisting of three cells with fills in counterflow and crossflow respectively. The results of these tests are shown respectively in figures (a) and (b) as a function of different wind directions and ratios of wind speed(measured 10 m aboveground level)to plume exhaust speed Vw/Vp．The percentage recirculation is less for the counterflow arrangement than for the crossflow arrangement．When a diffuser was added to the counterflow unit a reduction in recirculation was observed．Figure : Recirculation in three-cell counterflow and crossflow cooling tower.A further set of tests was conducted by Ribier in which two rows of counterflow cooling towers each consisting of three ceils were first arranged end to end (six ceils) and then systematically spaced one, two and three cells apart. Of these tests the continuous row of six cells experienced most recirculation with results as shown in figure . Recirculation appears to be a maximum at Vw/Vp ＝.Figure : Recirculation in six-cell cooling tower.Figure : Recirculation in a counterflow cooling tower consisting of two three-cell rows, two cellsapart.As shown in figure recirculation is considerably reduced when the two rows of three cells each are separated by a distance of two cells. Further separation does not reduce recirculation much.By placing two rows of three cells each side by side, recirculation is relatively high as shown in figure .Figure : Recirculation in cooling tower consisting of two rows of three cells located side by side.If the two rows of three cells are separated by one cell width only a relatively small reduction in maximum recirculation is experienced as is shown in figure .Based on these results it may be concluded that a row of induced draft cooling tower cells should be arranged in-line with the prevailing wind direction. A high air outlet velocity and the addition of a diffuser will also tend to reduce recirculation.Bender et al. [97BE1] numerically analyzed the air flow into a counterflow induced draft cooling tower consisting of two adjacent cells of the type shown in figure (b) with a view to reducing or eliminating ice formation at the tower inlet during windy periods in winter. The dimensions of the tower they studied were m (width), m (length) and m (height) with an intake height of m. The stack or diffuser diameter was m and its height was m.Ice build-up tends to be most prevelant at the windward facing intake where the entering air flow rate is higher than on the leeward intake. By placing a 10 percent porous wall m in height, m in front of the cooling tower inlet, the air flow entering on either intake was found to be essentially the same.Tesche [96TEl] conducted model tests to determine the effect of recirculation and interference on the performance of rows of induced draft hybrid cooling tower cells (similar to the unit or cell shown in figure ). His results are applicable in cases where the wind velocity distribution is given by Vw/Vwr = (Z/Zr). It is found that the recirculation of individual cells in a row consisting of twelve ceils varies as shown in figure . All wind speeds are specified at 10 m above ground level.Figure : Recirculation in cooling tower consisting of two rows of three cells separated by one cellwidth.Figure : Re, circulation in a row consisting of twelve hybrid cooling tower cells.The lowest recirculation is observed when the wind blows in the direction of the major axis of the cell row. The influence of the number of cells under these conditions is shown in figure .Figure : Recirculation as a function of number of cells in row.The influence of the ratio of wind speed to plume exhaust speed Vw/Vp on recirculation is shown in figure . A maximum recirculation occurs at a wind speed of 5 m/s.Figure : Recirculation as function of speed ratio.When two rows of six ceils each are placed next to each other with their major axes in parallel, the resultant average interference for different spacings between them is shown in figure . The interference for rows of twelve cells are shown in figure .Figure : Interference for two rows of six cells at different spacings.Figure : Interference for two rows of twelve ceils at different spacings.Recirculating plume air increases the effective wetbulb temperature at the inlet to the cooling tower as shown in figure . Since this increase is not only a function of the wetbulb temperature of the ambient air, but also of the thermodynamic state of the plume air, figure is at best an indication of the trend in wetbulb temperature change.Figure : Increase in wetbulb temperature due to recirculation.空冷热交换器和空冷塔(本文译自MR KROGER 的空冷热交换器和空冷塔一书 ，，）：热空气在空冷换热器中会出现回流现象，因此，会降低冷却效率，，为一个“X ”型空冷热交换器，在无风的情况下，有浮力的水蒸气在换热器中垂直上升。
外文及翻译---换热器的优化选型
毕业设计(论文)外文翻译外文题目New plate heat exchanger optimization Sel ection译文题目新型板式换热器的优化选型系部机械工程系换热器的优化选型W. Lub 和 S.A. Tassoub英国米德尔塞克斯，布鲁内尔大学机械设计工程部【摘要】板式换热器的优化选型是根据换热器的用途和工艺过程中的参数和NTU＝KA／MC＝△t／△tm，即传热单元数NTU和温差比（对数平均温差—换热的动力）选择板片形状、板式换热器的类型和结构。
【关键词】平均温差 NTU 板式蒸发器冷凝器1 平均温差△tm从公式Q＝K△tmA，△tm＝1／A ∫A（t1－t2）dA中可知，平均温差△tm是传热的驱动力，对于各种流动形式，如能求出平均温差，即板面两侧流体间温差对面积的平均值，就能出换热器的传热量。
平均温差是一个较为直观的概念，也是评价板式换热器性能的一项重要指标。
1.1 对数平均温差的计算当换热器传热量为dQ，温度上升为dt时，则C＝dQ／dt，将C定义为热容量，它表示单位时间通过单位面积交换的热量，即dQ＝K（th －tc）dA＝K△tdA，两种流体产生的温度变化分别为dth ＝－dQ／Ch，dtc＝－dQ／Cc，d△t＝d（th－tc）＝dQ（1／Cc －1／Ch）,则dA＝[1／k（1／Cc－1／Ch）]·（d△t／△t），当从A＝0积分至A＝A0时，A＝[1／k（1／Cc－1／Ch）]·㏑[（tho－tci）／（thi－tco）]，由于两种流体间交换的热量相等，即Q＝Ch （thi－tho）＝Cc（tco－tci），经简化后可知，Q＝KA0｛[（tho－tci）－（thi－tco）]／㏑[（tho－tci）／（thi－tco）]｝，若△t1＝t hi －tco，△t2＝tho－tci，则Q＝KA[（△t1－△t2）／㏑（△t1／△t2）]＝KA△tm，式中的△tm＝（△t1－△t2）／㏑（△t1／△t2）。
外文翻译及外文原文(参考格式)
外文翻译要求：1、外文资料与毕业设计（论文）选题密切相关，译文准确、质量好。
2、阅读2篇幅以上（10000字符左右）的外文资料，完成2篇不同文章的共2000汉字以上的英译汉翻译3、外文资料可以由指导教师提供，外文资料原则上应是外国作者。
严禁采用专业外语教材文章。
4、排序：“一篇中文译文、一篇外文原文、一篇中文译文、一篇外文原文”。
插图内文字及图名也译成中文。
5、标题与译文格式（字体、字号、行距、页边距等）与论文格式要求相同。
下页附：外文翻译与原文参考格式2英文翻译 (黑体、四号、顶格)外文原文出处：(译文前列出外文原文出处、作者、国籍，译文后附上外文原文)《ASHRAE Handbook —Refrigeration 》.CHAPTER3 .SYSTEM Practices for ammonia 3.1 System Selection 3.2 Equipment3.10 Reciprocating Compressors第3章 氨制冷系统的实施3.1 系统选择在选择一个氨制冷系统设计时，须要考虑一些设计决策要素，包括是否采用（1）单级压缩（2）带经济器的压缩（3）多级压缩（4）直接蒸发（5）满液式（6）液体再循环（7）载冷剂。
单级压缩系统基本的单级压缩系统由蒸发器、压缩机、冷凝器、储液器（假如用的话）和制冷剂控制装置（膨胀阀、浮球阀等）。
1997 ASHRAE 手册——“原理篇”中的第一章讨论了压缩制冷循环。
图1.壳管式经济器的布置外文翻译的标题与译文中的字体、字号、行距、页边距等与论文格式相同。
英文原文(黑体、四号、顶格)英文翻译2（黑体，四号，顶格）外文原文出处：（黑体，四号，顶格）P. Fanning. Nonlinear Models of Reinforced and Post-tensioned Concrete Beams. Lecturer, Department of Civil Engineering, University College Dublin. Received 16 Jul 2001.非线形模型钢筋和后张法预应力混凝土梁摘要:商业有限元软件一般包括混凝土在荷载做用下非线性反应的专用数值模型。
冷凝器英语
冷凝器condenser冷凝液condensate空冷式冷凝器air-cooled condenser风冷式冷凝器air-cooled condenser自然对流空冷式冷凝器natural convecton air-cooled condenser 强制通风式冷凝器forced draught condenser冷凝风机condensate fan线绕式冷凝器wire and tube condenser水冷式冷凝器water-cooled condenser沉浸式盘管冷凝器submerged coil condenser套管式冷凝器double pipe condenser壳管式冷凝器shell and tube condenser组合式冷凝器multishell condenser卧式壳管式冷凝器closed shell and tube condenser卧式冷凝器closed condenser立式壳管式冷凝器open shell and tube condenser立式冷凝器open condenser，vertical condenser壳盘管式冷凝器shell and coil condenser分隔式冷凝器split condenser淋激式冷凝器atmospheric condenser溢流式冷凝器bleeder-type condenser蒸发式冷凝器evaporative condenser板式冷凝器plate-type condenser空冷板式冷凝器air-cooled plate-type condenser水冷板式冷凝器water-cooled plate-type condenser焊接板式冷凝器welded sheet condenser螺旋板式冷凝器spiral sheet condenser冷凝-贮液器condenser-receiver混合式冷凝器barometric condenser液化器liquefier冷凝水泵condensate pump冷凝器梳condensate comb预冷盘管desuperheating coil过冷器subcooler中间冷却器intercooler盐水冷却器brine cooler气-液回热器liquid or suction heat exchanger回热器superheater紊流器turbulator预冷器precooler级间冷却器interstage cooler饮水冷却器drinking-water cooler喷泉式饮水冷却器bubbler-type drinking water cooler 冷藏间冷却器cold-storage cooler盐水（水）冷却器brine（water）cooler空气冷却器air cooler，forced draught干式空气冷却器dry-type air cooler强制循环空气冷却器forced-circulation air cooler自然对流空气冷却器natural-convection air cooler空气冷却机组air-cooler unit蒸发盘管干燥盘管drier coil冷却盘管cooling coil蒸发盘管expansion coil蓄冷盘管hold-voer coil直接蒸发盘管direct expansion coil制冷剂分配器refrigerant distributor支承板tube support蓄冷板hold-over plate共晶混合物板eutectic plate折流板baffle滴水盘drip tray冷藏库排管冷却排管cooling coil，cooling grid冷却排管组cooling battery顶排管overhead coil墙排管wall coil，wall grid蓄冷排管hold-over coil，hold-over grid蓄冷板hold-over plate。
毕业设计英文 翻译(原文)
编号：毕业设计(论文)外文翻译（原文）院（系）：桂林电子科技大学专业：电子信息工程学生姓名： xx学号： xxxxxxxxxxxxx 指导教师单位：桂林电子科技大学姓名： xxxx职称： xx2014年x月xx日Timing on and off power supplyusesThe switching power supply products are widely used in industrial automation and control, military equipment, scientific equipment, LED lighting, industrial equipment,communications equipment,electrical equipment,instrumentation, medical equipment, semiconductor cooling and heating, air purifiers, electronic refrigerator, LCD monitor, LED lighting, communications equipment, audio-visual products, security, computer chassis, digital products and equipment and other fields.IntroductionWith the rapid development of power electronics technology, power electronics equipment and people's work, the relationship of life become increasingly close, and electronic equipment without reliable power, into the 1980s, computer power and the full realization of the switching power supply, the first to complete the computer Power new generation to enter the switching power supply in the 1990s have entered into a variety of electronic, electrical devices, program-controlled switchboards, communications, electronic testing equipment power control equipment, power supply, etc. have been widely used in switching power supply, but also to promote the rapid development of the switching power supply technology .Switching power supply is the use of modern power electronics technology to control the ratio of the switching transistor to turn on and off to maintain a stable output voltage power supply, switching power supply is generally controlled by pulse width modulation (PWM) ICs and switching devices (MOSFET, BJT) composition. Switching power supply and linear power compared to both the cost and growth with the increase of output power, but the two different growth rates. A power point, linear power supply costs, but higher than the switching power supply. With the development of power electronics technology and innovation, making the switching power supply technology to continue to innovate, the turning points of this cost is increasingly move to the low output power side, the switching power supply provides a broad space for development.The direction of its development is the high-frequency switching power supply, high frequency switching power supply miniaturization, and switching power supply into a wider range of application areas, especially in high-tech fields, and promote the miniaturization of high-tech products, light of. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.classificationModern switching power supply, there are two: one is the DC switching power supply; the other is the AC switching power supply. Introduces only DC switching power supply and its function is poor power quality of the original eco-power (coarse) - such as mains power or battery power, converted to meet the equipment requirements of high-quality DC voltage (Varitronix) . The core of the DC switching power supply DC / DC converter. DC switching power supply classification is dependent on the classification of DC / DC converter. In other words, the classification of the classification of the DC switching power supply and DC/DC converter is the classification of essentially the same, the DC / DC converter is basically a classification of the DC switching power supply.DC /DC converter between the input and output electrical isolation can be divided into two categories: one is isolated called isolated DC/DC converter; the other is not isolated as non-isolated DC / DC converter.Isolated DC / DC converter can also be classified by the number of active power devices. The single tube of DC / DC converter Forward (Forward), Feedback (Feedback) two. The double-barreled double-barreled DC/ DC converter Forward (Double Transistor Forward Converter), twin-tube feedback (Double Transistor Feedback Converter), Push-Pull (Push the Pull Converter) and half-bridge (Half-Bridge Converter) four. Four DC / DC converter is the full-bridge DC / DC converter (Full-Bridge Converter).Non-isolated DC / DC converter, according to the number of active power devices can be divided into single-tube, double pipe, and four three categories. Single tube to a total of six of the DC / DC converter, step-down (Buck) DC / DC converter, step-up (Boost) DC / DC converters, DC / DC converter, boost buck (Buck Boost) device of Cuk the DC / DC converter, the Zeta DC / DC converter and SEPIC, the DC / DC converter. DC / DC converters, the Buck and Boost type DC / DC converter is the basic buck-boost of Cuk, Zeta, SEPIC, type DC / DC converter is derived from a single tube in this six. The twin-tube cascaded double-barreled boost (buck-boost) DC / DC converter DC / DC converter. Four DC / DC converter is used, the full-bridge DC / DC converter (Full-Bridge Converter).Isolated DC / DC converter input and output electrical isolation is usually transformer to achieve the function of the transformer has a transformer, so conducive to the expansion of the converter output range of applications, but also easy to achieve different voltage output , or a variety of the same voltage output.Power switch voltage and current rating, the converter's output power is usually proportional to the number of switch. The more the number of switch, the greater the output power of the DC / DC converter, four type than the two output power is twice as large,single-tube output power of only four 1/4.A combination of non-isolated converters and isolated converters can be a single converter does not have their own characteristics. Energy transmission points, one-way transmission and two-way transmission of two DC / DC converter. DC / DC converter with bi-directional transmission function, either side of the transmission power from the power of lateral load power from the load-lateral side of the transmission power.DC / DC converter can be divided into self-excited and separately controlled. With the positive feedback signal converter to switch to self-sustaining periodic switching converter, called self-excited converter, such as the the Luo Yeer (Royer,) converter is a typical push-pull self-oscillating converter. Controlled DC / DC converter switching device control signal is generated by specialized external control circuit.the switching power supply.People in the field of switching power supply technology side of the development of power electronic devices, while the development of the switching inverter technology, the two promote each other to promote the switching power supply annual growth rate of more than two digits toward the light, small, thin, low-noise, high reliability, the direction of development of anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, AC / AC DC / AC, such as inverters, DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardization, and has been recognized by the user, but AC / DC modular, its own characteristics make the modular process, encounter more complex technology and manufacturing process. Hereinafter to illustrate the structure and characteristics of the two types of switching power supply.Self-excited: no external signal source can be self-oscillation, completely self-excited to see it as feedback oscillation circuit of a transformer.Separate excitation: entirely dependent on external sustain oscillations, excited used widely in practical applications. According to the excitation signal structure classification; can be divided into pulse-width-modulated and pulse amplitude modulated two pulse width modulated control the width of the signal is frequency, pulse amplitude modulation control signal amplitude between the same effect are the oscillation frequency to maintain within a certain range to achieve the effect of voltage stability. The winding of the transformer can generally be divided into three types, one group is involved in the oscillation of the primary winding, a group of sustained oscillations in the feedback winding, there is a group of load winding. Such as Shanghai is used in household appliances art technological production of switching power supply, 220V AC bridge rectifier, changing to about 300V DC filter added tothe collector of the switch into the transformer for high frequency oscillation, the feedback winding feedback to the base to maintain the circuit oscillating load winding induction signal, the DC voltage by the rectifier, filter, regulator to provide power to the load. Load winding to provide power at the same time, take up the ability to voltage stability, the principle is the voltage output circuit connected to a voltage sampling device to monitor the output voltage changes, and timely feedback to the oscillator circuit to adjust the oscillation frequency, so as to achieve stable voltage purposes, in order to avoid the interference of the circuit, the feedback voltage back to the oscillator circuit with optocoupler isolation.technology developmentsThe high-frequency switching power supply is the direction of its development, high-frequency switching power supply miniaturization, and switching power supply into the broader field of application, especially in high-tech fields, and promote the development and advancement of the switching power supply, an annual more than two-digit growth rate toward the light, small, thin, low noise, high reliability, the direction of the anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, the DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardized, and has been recognized by the user, but modular AC / DC, because of its own characteristics makes the modular process, encounter more complex technology and manufacturing process. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.The switching power supply applications in power electronic devices as diodes, IGBT and MOSFET.SCR switching power supply input rectifier circuit and soft start circuit, a small amount of applications, the GTR drive difficult, low switching frequency, gradually replace the IGBT and MOSFET.Direction of development of the switching power supply is a high-frequency, high reliability, low power, low noise, jamming and modular. Small, thin, and the key technology is the high frequency switching power supply light, so foreign major switching power supply manufacturers have committed to synchronize the development of new intelligent components, in particular, is to improve the secondary rectifier loss, and the power of iron Oxygen materials to increase scientific and technological innovation in order to improve the magnetic properties of high frequency and large magnetic flux density (Bs), and capacitor miniaturization is a key technology. SMT technology allows the switching power supply has made considerable progress, the arrangement of the components in the circuit board on bothsides, to ensure that the light of the switching power supply, a small, thin. High-frequency switching power supply is bound to the traditional PWM switching technology innovation, realization of ZVS, ZCS soft-switching technology has become the mainstream technology of the switching power supply, and a substantial increase in the efficiency of the switching power supply. Indicators for high reliability, switching power supply manufacturers in the United States by reducing the operating current, reducing the junction temperature and other measures to reduce the stress of the device, greatly improve the reliability of products.Modularity is the overall trend of switching power supply, distributed power systems can be composed of modular power supply, can be designed to N +1 redundant power system, and the parallel capacity expansion. For this shortcoming of the switching power supply running noise, separate the pursuit of high frequency noise will also increase, while the use of part of the resonant converter circuit technology to achieve high frequency, in theory, but also reduce noise, but some The practical application of the resonant converter technology, there are still technical problems, it is still a lot of work in this field, so that the technology to be practical.Power electronics technology innovation, switching power supply industry has broad prospects for development. To accelerate the pace of development of the switching power supply industry in China, it must take the road of technological innovation, out of joint production and research development path with Chinese characteristics and contribute to the rapid development of China's national economy.Developments and trends of the switching power supply1955 U.S. Royer (Roger) invented the self-oscillating push-pull transistor single-transformer DC-DC converter is the beginning of the high-frequency conversion control circuit 1957 check race Jen, Sen, invented a self-oscillating push-pull dual transformers, 1964, U.S. scientists canceled frequency transformer in series the idea of switching power supply, the power supply to the size and weight of the decline in a fundamental way. 1969 increased due to the pressure of the high-power silicon transistor, diode reverse recovery time shortened and other components to improve, and finally made a 25-kHz switching power supply.At present, the switching power supply to the small, lightweight and high efficiency characteristics are widely used in a variety of computer-oriented terminal equipment, communications equipment, etc. Almost all electronic equipment is indispensable for a rapid development of today's electronic information industry power mode. Bipolar transistor made of 100kHz, 500kHz power MOS-FET made, though already the practical switching power supply is currently available on the market, but its frequency to be further improved. Toimprove the switching frequency, it is necessary to reduce the switching losses, and to reduce the switching losses, the need for high-speed switch components. However, the switching speed will be affected by the distribution of the charge stored in the inductance and capacitance, or diode circuit to produce a surge or noise. This will not only affect the surrounding electronic equipment, but also greatly reduce the reliability of the power supply itself. Which, in order to prevent the switching Kai - closed the voltage surge, RC or LC buffers can be used, and the current surge can be caused by the diode stored charge of amorphous and other core made of magnetic buffer . However, the high frequency more than 1MHz, the resonant circuit to make the switch on the voltage or current through the switch was a sine wave, which can reduce switching losses, but also to control the occurrence of surges. This switch is called the resonant switch. Of this switching power supply is active, you can, in theory, because in this way do not need to greatly improve the switching speed of the switching losses reduced to zero, and the noise is expected to become one of the high-frequency switching power supply The main ways. At present, many countries in the world are committed to several trillion Hz converter utility.the principle of IntroductionThe switching power supply of the process is quite easy to understand, linear power supplies, power transistors operating in the linear mode and linear power, the PWM switching power supply to the power transistor turns on and off state, in both states, on the power transistor V - security product is very small (conduction, low voltage, large current; shutdown, voltage, current) V oltammetric product / power device is power semiconductor devices on the loss.Compared with the linear power supply, the PWM switching power supply more efficient process is achieved by "chopping", that is cut into the amplitude of the input DC voltage equal to the input voltage amplitude of the pulse voltage. The pulse duty cycle is adjusted by the switching power supply controller. Once the input voltage is cut into the AC square wave, its amplitude through the transformer to raise or lower. Number of groups of output voltage can be increased by increasing the number of primary and secondary windings of the transformer. After the last AC waveform after the rectifier filter the DC output voltage.The main purpose of the controller is to maintain the stability of the output voltage, the course of their work is very similar to the linear form of the controller. That is the function blocks of the controller, the voltage reference and error amplifier can be designed the same as the linear regulator. Their difference lies in the error amplifier output (error voltage) in the drive before the power tube to go through a voltage / pulse-width conversion unit.Switching power supply There are two main ways of working: Forward transformand boost transformation. Although they are all part of the layout difference is small, but the course of their work vary greatly, have advantages in specific applications.the circuit schematicThe so-called switching power supply, as the name implies, is a door, a door power through a closed power to stop by, then what is the door, the switching power supply using SCR, some switch, these two component performance is similar, are relying on the base switch control pole (SCR), coupled with the pulse signal to complete the on and off, the pulse signal is half attentive to control the pole voltage increases, the switch or transistor conduction, the filter output voltage of 300V, 220V rectifier conduction, transmitted through the switching transformer secondary through the transformer to the voltage increase or decrease for each circuit work. Oscillation pulse of negative semi-attentive to the power regulator, base, or SCR control voltage lower than the original set voltage power regulator cut-off, 300V power is off, switch the transformer secondary no voltage, then each circuit The required operating voltage, depends on this secondary road rectifier filter capacitor discharge to maintain. Repeat the process until the next pulse cycle is a half weeks when the signal arrival. This switch transformer is called the high-frequency transformer, because the operating frequency is higher than the 50HZ low frequency. Then promote the pulse of the switch or SCR, which requires the oscillator circuit, we know, the transistor has a characteristic, is the base-emitter voltage is 0.65-0.7V is the zoom state, 0.7V These are the saturated hydraulic conductivity state-0.1V-0.3V in the oscillatory state, then the operating point after a good tune, to rely on the deep negative feedback to generate a negative pressure, so that the oscillating tube onset, the frequency of the oscillating tube capacitor charging and discharging of the length of time from the base to determine the oscillation frequency of the output pulse amplitude, and vice versa on the small, which determines the size of the output voltage of the power regulator. Transformer secondary output voltage regulator, usually switching transformer, single around a set of coils, the voltage at its upper end, as the reference voltage after the rectifier filter, then through the optocoupler, this benchmark voltage return to the base of the oscillating tube pole to adjust the level of the oscillation frequency, if the transformer secondary voltage is increased, the sampling coil output voltage increases, the positive feedback voltage obtained through the optocoupler is also increased, this voltage is applied oscillating tube base, so that oscillation frequency is reduced, played a stable secondary output voltage stability, too small do not have to go into detail, nor it is necessary to understand the fine, such a high-power voltage transformer by switching transmission, separated and after the class returned by sampling the voltage from the opto-coupler pass separated after class, so before the mains voltage, and after the classseparation, which is called cold plate, it is safe, transformers before power is independent, which is called switching power supply.the DC / DC conversionDC / DC converter is a fixed DC voltage transformation into a variable DC voltage, also known as the DC chopper. There are two ways of working chopper, one Ts constant pulse width modulation mode, change the ton (General), the second is the frequency modulation, the same ton to change the Ts, (easy to produce interference). Circuit by the following categories:Buck circuit - the step-down chopper, the average output voltage U0 is less than the input voltage Ui, the same polarity.Boost Circuit - step-up chopper, the average output voltage switching power supply schematic U0 is greater than the input voltage Ui, the same polarity.Buck-Boost circuit - buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, the inductance transmission.Cuk circuit - a buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, capacitance transmission.The above-mentioned non-isolated circuit, the isolation circuit forward circuits, feedback circuit, the half-bridge circuit, the full bridge circuit, push-pull circuit. Today's soft-switching technology makes a qualitative leap in the DC / DC the U.S. VICOR company design and manufacture a variety of ECI soft-switching DC / DC converter, the maximum output power 300W, 600W, 800W, etc., the corresponding power density (6.2 , 10,17) W/cm3 efficiency (80-90)%. A the Japanese Nemic Lambda latest using soft-switching technology, high frequency switching power supply module RM Series, its switching frequency (200 to 300) kHz, power density has reached 27W/cm3 with synchronous rectifier (MOSFETs instead of Schottky diodes ), so that the whole circuit efficiency by up to 90%.AC / DC conversionAC / DC conversion will transform AC to DC, the power flow can be bi-directional power flow by the power flow to load known as the "rectification", referred to as "active inverter power flow returned by the load power. AC / DC converter input 50/60Hz AC due must be rectified, filtered, so the volume is relatively large filter capacitor is essential, while experiencing safety standards (such as UL, CCEE, etc.) and EMC Directive restrictions (such as IEC, FCC, CSA) in the AC input side must be added to the EMC filter and use meets the safety standards of the components, thus limiting the miniaturization of the volume of AC / DC power, In addition, due to internal frequency, high voltage, current switching, making the problem difficult to solve EMC also high demands on the internal high-density mountingcircuit design, for the same reason, the high voltage, high current switch makes power supply loss increases, limiting the AC / DC converter modular process, and therefore must be used to power system optimal design method to make it work efficiency to reach a certain level of satisfaction.AC / DC conversion circuit wiring can be divided into half-wave circuit, full-wave circuit. Press the power phase can be divided into single-phase three-phase, multiphase. Can be divided into a quadrant, two quadrant, three quadrants, four-quadrant circuit work quadrant.he selection of the switching power supplySwitching power supply input on the anti-jamming performance, compared to its circuit structure characteristics (multi-level series), the input disturbances, such as surge voltage is difficult to pass on the stability of the output voltage of the technical indicators and linear power have greater advantages, the output voltage stability up to (0.5)%. Switching power supply module as an integrated power electronic devices should be selected。
冷凝器(Condenser)
冷凝器(Condenser)一种机件，可以将管子中的热量，快速的传到管子附近的空气，汽车大部分置于水箱前方。
把气体或蒸气转变成液体的装置。
发电厂要用许多冷凝器使涡轮机排出的蒸气得到冷凝；在冷冻厂中用冷凝器来冷凝氨和氟利昂之类的致冷蒸气。
石油化学工业中用冷凝器使烃类及其他化学蒸气冷凝。
在蒸馏过程中，把蒸气转变成液态的装置称为冷凝器。
所有的冷凝器都是把气体或蒸气的热量带走而运转的。
山东万合制冷设备有限公司。
原理对某些应用来说，气体必须通过一根长长的管子（通常盘成螺线管），以便让热量散失到四周的空气中，铜之类的导热金属常用于输送蒸气。
为提高冷凝器的效率经常在管道上附加散热片以加速散热。
散热片是用良导热金属制成的平板。
这类冷凝器一般还要用风机迫使空气经过散热片并把热带走。
一般制冷机的制冷原理压缩机的作用是把压力较低的蒸汽压缩成压力较高的蒸汽，使蒸汽的体积减小，压力升高。
压缩机吸入从蒸发器出来的较低压力的工质蒸汽，使之压力升高后送入冷凝器，在冷凝器中冷凝成压力较高的液体，经节流阀节流后，成为压力较低的液体后，送入蒸发器，在蒸发器中吸热蒸发而成为压力较低的蒸汽，从而完成制冷循环。
蒸汽压缩式单级蒸汽压缩制冷系统，是由制冷压缩机、冷凝器、蒸发器和节流阀四个基本部件组成。
它们之间用管道依次连接，形成一个密闭的系统，制冷剂在系统中不断地循环流动，发生状态变化，与外界进行热量交换。
制冷系统液体制冷剂在蒸发器中吸收被冷却的物体热量之后，汽化成低温低压的蒸汽、被压缩机吸入、压缩成高压高温的蒸汽后排入冷凝器、在冷凝器中向冷却介质(水或空气)放热，冷凝为高压液体、经节流阀节流为低压低温的制冷剂、再次进入蒸发器吸热汽化，达到循环制冷的目的。
这样，制冷剂在系统中经过蒸发、压缩、冷凝、节流四个基本过程完成一个制冷循环。
在制冷系统中，蒸发器、冷凝器、压缩机和节流阀是制冷系统中必不可少的四大件，这当中蒸发器是输送冷量的设备。
制冷剂在其中吸收被冷却物体的热量实现制冷。
专业英语2.句子翻译
Condenser is a large surface-type heat exchanger; the steam is condensed by transferring its latent heat to circulating water.冷凝器是种大表面型换热器，排气在其中被冷凝，将其汽化潜热传给循环水Deaerator is usually operated at a pressure higher than atmospheric.除氧器通常是在高于大气压下运行Since the water in deaerator is at its boiling point, it’s important that boiler-feed pump be located a considerable distance below the deaerator, to avoid flashing of water in the boiler-feed pump suction.由于除氧器的水达到了沸点，为了避免水冲击，锅炉给水泵和除氧器之间有一定的距离By utilizing microelectronic technology, the inverter-driven conditioners, which offer constant room temperature and other comfortable functions, were developed.利用微电子技术，变频空调提供恒定的房间温度和其他舒适的功能已被开发CFCs issue must also be solved within the earliest frame possibleIn recent years, a large number of domestic and commercial products were found not to be environmentally friendly.近些年，发现大量对环境不友好的家用和商用的产品Quick and easy installation and higher reliability have been the main requirements for the small shop and office application在小型商店和办公室的应用中，（对空调的）主要要求是快速（制冷）、容易安装和具有较高的可靠性“Energy saving”, “comfort”, “versatility”, and “adaptation to various ecological requirements”have been becoming the key issue of air conditioning equipment and system节能、舒适、多功能和对不同生态需求的适用性已成为空调装置和系统领域的主要技术发展趋势To adapt customers requirements, recent air conditioning trends are requiring the manufacturer not only develop system equipment but alsoengages in the developments of the system itself including the controller and the connection piping and so on为了适应顾客的需求，目前空调发展的另一个趋势是不仅要开发空调装置还要开发空调系统本身，包括控制器、连接管线等Three halocarbon refrigerants-R-22,R-123 and R-134a, are widely available today for commercial air-conditioning application and represent acceptable alternatives to CFCs. None is perfect from an environmental viewpoint, but all are significantly better than CFCs.三种卤代烃制冷制R22、R123和R134a，目前被商业空调广泛接受和代表可接受的氟氯烃的替代品。
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氨制冷系统的节能设计，改造和蒸发式冷凝器的控制阿卜杜勒穆罕默德和凯利，工业评估中心，代顿大学摘要氨制冷系统通常提供了许多节能商机，因为他们的大动力消耗，运行时间长的和动态的操作。
氨制冷系统的能源使用高度依赖于冷凝头的压力，而这是一个函数的蒸发式冷凝器容量和控制功能。
本文研究系统能源利用中聚光能力和冷凝器的控制之间的关系。
它首先开发方法来确定冷凝器的性能，然后以仿真模型模拟压缩机和冷凝器风扇的年度能源利用。
，它使用工程基本面和经验两个数据，准确地捕捉压缩机，冷凝器和环境湿球温度之间的协同效应。
节约能源是三种情况：安装在冷凝器风机变频驱动器，采用湿球控制方法战略和提高聚光性能。
以说明气候的影响，这些模拟是两个不同的ASHRAE气候区，迈阿密，佛罗里达州和执行明尼阿波利斯，明尼苏达州，这是炎热和寒冷的气候分别。
结果表明，提高表现不佳的冷凝器的性能是最经济有效的节能测量。
但是节约能源从冷凝器安装变频驱动器球迷和利用湿球的方法策略取决于环境气候条件，与位置无关。
接下来，内部收益率的计算方法来安装额外的聚光能力超越在为相同的两个ASHRAE气候区新建筑应用的标准做法。
结果表明，安装两次基线聚光能力，内部收益率超过20 ％。
综上所述，本文提出的设计，改造的综合方法在氨制冷系统蒸发式冷凝器的控制权。
节约能源衍生通过使用这种方法可以显著提高氨的能量效率制冷系统。
介绍约7.5 ％的总生产能耗用于食品加工行业，其中约21％的能量是电能(二零零六年环评)。
在这些设备中，氨制冷系统是最大的能源消耗部分。
制冷与冷却工艺所用电量是食品加工行业(二零零六年EIA)的用电量的27％。
制冷系统使用的能量是高度依赖于冷凝压力，而这又是冷凝器容量和控制性能。
因此，提高聚光能力和控制可导致显著的节能效果。
本文首先确定使用的数据从实际的聚光性能制冷控制系统。
然后是开发仿真模型来计算每年的能源使用所研究的压缩机和冷凝器风扇。
该仿真模型，用来计算节能三个节能措施(ECMS)：在冷凝器风扇安装变频器，采用湿球的方法策略，提高聚光性能。
以说明气候的影响，这些仿真用于执行迈阿密，佛罗里达州和明尼苏达州明尼阿波利斯，这是炎热和寒冷的气候分别。
文章最后决定回报的安装额外的容量超出标准规范的内部收益率在新的建筑应用。
系统说明分析系统是一个两阶段的氨制冷系统具有两个低压侧压缩机和两个高级压缩机。
所有的压缩机是螺杆式与滑阀控制和热虹吸油冷却。
一种蒸发式冷凝器以恒定的速度从系统散发热量。
对于本文的其余部分，术语系统将参考冷凝器风扇和压缩机。
从冷凝器泵的能源使用小，并且不评价了本文。
关键系统参数，包括电动机电流，氨的压力和温度从制冷控制系统获得。
氨性数据的计算使用参考流体热力学和输运性质数据(NIST ，2010)也被称为REFPROP 。
图中显示了制冷系统的替补的示意图。
图1。
电路图制冷系统的pH值图上计算排热到冷凝器冷凝压力是决定系统能源利用的一个关键变量。
为了准确地计算冷凝压力，冷凝器性能必须确定。
在第一步骤中确定冷凝器性能是计算从压缩机排出到总热量冷凝器。
在系统中的能量平衡显示了总的热拒绝了冷凝器是由低和高级压缩机加两个设置在制冷（QREF0）低和高级压缩机两者的压缩或轴功率（WS）的热量。
QCond.actual = ΣQrefLS +ΣQrefHS +ΣWSLS +ΣWsHS （1）所有的热拒绝从低温压缩机减去热虹吸拒绝的低级压缩机油冷却（TSOC ，LS）将被转移到高压侧制度。
因此，由高温压缩机提供（TRprovided ，HS）的制冷是：ΣTRprovided ，HS = ΣQrefLS +ΣQrefHS +ΣWLS - ΣTSOC ，LS （ 2 ）冷凝器必须从高级的制冷和轴功率该热压缩机，加上从低级侧压缩机TSOC 。
因此，散热到冷凝器由三个主成分：QCond.actual = ΣTRprovided ，HS + ΣWsHS + ΣTSOC ，LS （3 ）制冷高级阶段压缩机（TRprovided ，HS）提供制造商提供的额定制冷量的或额定吨（TR ）压缩机的吸入范围和冷凝温度。
此数据可以被嵌入到一个二阶与交互项多项式方程（Manske 2000），以确定额定在给定的吸气能力和冷凝温度为：TR = C0 + C1 •Tcond + C2 •TSUC + C11 •Tcond ²+ C22 •TSUC ²+ C12 •Tcond •TSUC （4 ）压缩机的百分制冷容量的滑阀百分比的函数打开的位置，但它们不相同。
在这种情况下，百分之制冷容量为函数滑阀位置的示于图2。
该数据被从制冷得到控制系统。
该曲线是相似的一个报告Stoecker （1998）。
图2。
部分容量与分数公开赛滑阀位置吸气和冷凝温度所使用的各自的压力测定和氨的属性数据。
压缩机的实际制冷容量可以使用等式4和来自控制系统的百分之制冷容量，计算如下：QREF = Qrrated •％容量（5 ）压缩热由高温级压缩机（WsHS）生产来自控制系统的数据而获得的每个压缩机的电机电流。
至相关电机电流轴功率（WS），电机电流和输入之间的关系权力必须得到发展。
这种关系中，可以从点测量开发电机电流和输入功率在整个压缩机的工作范围。
通过使用的压缩机（ὴm ）的两个铭牌效率和f （A ），轴功率或等价每个压缩机的压缩热量可以计算为：WsHS = F（A ）* ὴm （6 ）热虹吸油冷却（TSOC）考虑了两阶段的低温循环在图1中表示的氨制冷系统。
在状态1LS ，氨进入压缩机作为饱和蒸汽和离开压缩机的过热蒸汽在状态2LS 。
路径1LS - 2LS表示压缩热。
理想情况下，热量被排出到下一阶段将在点2LS和3LS的焓差。
然而，一些热量损失到压缩机油，并在压缩机的出口处的制冷剂的实际温度是在点2aLS而不是2LS 。
在点2aLS的温度和压力，从控制已知系统数据，因此焓点2aLS可以使用属性数据来确定氨的低级压缩机压缩的高温，WSLS ，也可以使用计算式（6）。
通过对压缩机施加能量平衡放电转移到热在热虹吸油冷却系统可以计算如下：TSOC ，LS = WSLS - mref.LS •（h2a.LS - h1.LS ）（7 ）制冷剂通过低压侧的压缩机质量流量可以计算如下：MREF -LS = Qref.LS / （h1.LS - h4.LS ）（8）通常，制造商报告的体积流量的空气速率，标称容量，并且热抑制因子（HRF ）。
体积流量是用于使用计算的质量流率空气的密度在标准条件。
该HRF ，这既是外部空气湿球温度计的功能温度（TWB）和饱和冷凝温度（Tcond ），用于确定在额定容量冷凝器对于一个给定TWB和Tcond为（Manske ，Reindl和2001年克莱因）：额定电容容量=标称容量/ HRF （ TWB ，Tcond ）（ 10 ）等式9b和10可以适用于制造商的规格为蒸发冷凝器，以确定对于一个给定的湿球Tcond和效力之间的关系范围。
有效性被发现是线性相关的Tcond为：effM = E0 - E1 · Tcond （ 11 ）由于蒸发式冷凝器的运行期间的实际容量已计算的，实际效果可以适合于在等式11的形式的线。
测量效力与从所研究的系统Tcond数据被绘制时，无论是蒸发式冷凝器，风机和水泵是在图3满负荷生产。
额定制造商从式（11）效果也绘制在同一张图来比较的有效性上一个新的蒸发式冷凝器，以其中一个已经服役了几年。
图3表示该蒸发式冷凝器性能已劣化随着时间的推移。
实际容量比制造商的额定容量少约40％。
此信息可以被用作用于模拟程序的校准参数。
例如，在图3中，冷凝器容量为一个新的冷凝器将约为1.69倍，目前的实际能力。
图3。
实际和制造商有效性的蒸发式冷凝器模拟年能源消耗每年的能量使用的制冷系统的是压缩机和冷凝器的总和风机能耗。
冷凝压力是必须正确地计算一个关键的变量正确模拟压缩机和冷凝器风扇的能源使用。
以下步骤概述一方法计算压缩机功率，冷凝压力和冷凝器风扇电源。
计算压缩机输入功率一个给定的压缩机在一定范围抽吸的额定轴功率（ bhprated ）和冷凝温度可以从制造商处获得。
此数据可以被嵌入到一个二阶多项式方程的交互项来确定额定满载轴功率在给定的吸气和冷凝温度（ Manske 2000），如：bhprated = P0 + P1 • Tcond + P2 • TSUC + P11 • Tcond ² + P22 • TSUC ² + P12 • Tcond • TSUC （ 12 ）在该制冷系统中的压缩机，像许多制冷系统中，在操作碱/修剪方式，表示过去压缩机接通的每个阶段是修剪压缩机。
式（4），它类似于公式12中，示出的满负荷容量压缩机吸入的函数和冷凝温度下，该压缩机运行。
知道制冷负荷（参考负载）和碱的量被操作（Σ TRBase ），则该部分的容量修剪压缩机的压缩机定阶段（ FCTrim ）可以计算如下：FCTrim = （参考负载 - Σ TRBase ） / TRTrim （ 13 ）如果基压缩机的容量大于或等于该致冷负荷，然后由基座压缩机提供的制冷为零。
通常情况下，压缩机的部分负荷功率变化的基础上部分的容量和压力比。
最好是确定采用现场每台压缩机的部分负荷电源测量。
上述压缩机在这种分析中，一个典型的部分负荷的部分负荷功率性能曲线是用来（1998 Stoecker ）。
压缩机的部分功率是下面的表格：FP = A0 + A1 • FC + A2 • FC2 + A3 • FC3 + A4 •镨（ 14 ）要修剪压缩机，制动马力在部分负荷可以建模为：bhpact = bhprated ，修剪• FP （ 15 ）使用电机的额定效率，每台压缩机的计算轴功率，总投入所有压缩机（ΣPCompressors ）的功率，单位为千瓦，可以计算为：Σ PCompressors = Σ bhpact / ὴm • 0.746 （千瓦/马力）（ 16 ）计算的冷凝压力的蒸发冷凝器随着冷凝温度的容量的增加和环境湿球温度下降。
此外，电力的消耗压缩机的增加而增加，冷凝温度和制冷负荷。
能源利用两个冷凝器和压缩机的变化与冷凝温度显著的;准确地确定实际操作的冷凝温度是必不可少的量化能源利用系统。
图5示出了冷凝器的冷却能力高和低的湿球温度和从压缩机的高和低制冷负荷在一定范围内的散热冷凝温度。
矩形显示出所在的聚光能力和压缩机散热是相等的。
请注意，对于低的湿球温度和低的制冷负荷，冷凝器有足够的能力来拒绝压缩机的热量还要低冷凝压力。
然而，在实践中大多数制冷系统不能在冷凝压力下操作90 psig的或更少由于系统的限制。
因此，在冷凝压力设定点保持通过控制冷凝器风机和泵的最低冷凝压力。