专业英语翻译1

第二课1）An atom's nucleus can be split apart。

When this is done, a tremendous amount of energy is released。

The energy is both heat and light energy。

Einstein said that a very small amount of matter contains a very large amount of energy。

This energy, when let out slowly, can be harnessed to generate electricity。

When it is let out all at once, it can make a tremendous explosion in an atomic bomb. 原子核能够分裂。

当原子核分裂完，将会释放巨大的能量。

这些能量既有热能也有光能。

爱因斯坦说过一个很小的物质也包含了很大的能量。

当这些能量被缓慢的释放时，可以用来发电。

当这些能量被迅速的释放时，那么能产生原子弹中的巨大的爆炸。

2）A nuclear power plant (As shown in Fig.3.6 ) uses uranium as a "fuel。

" Uranium is an element that is dug out of the ground many places around the world.。

It is processed into tiny pellets that are loaded into very long rods that are put into the power plant's reactor.核电站使用铀作燃料。

铀是一种在世界各地的许多地方都能挖出的一种元素。

它被加工成装载在很长棒中的小环然后在
投放在核电站的反应堆中。

3）The word fission means to split apart.。

Inside the reactor of an atomic power plant, uranium atoms are split apart in a controlled chain reaction.这个单词裂变意思就是分裂。

在原子
核电站反应堆中，铀原子在控制链反应中分裂。

4）In a chain reaction, particles released by the splitting of the atom go off and strike other uranium atoms splitting those。

Those particles given off split still other atoms in a chain reaction, in nuclear power plants, control rods are used to keep the splitting regulated so it doesn't go too fast.在链式反应中，铀原子爆裂释放出来的粒子离开铀原子并且撞击其他铀原子分裂成粒子。

在链式反应中这些被释放的粒子继续爆裂其他的原子在核电站中，为了控制链式反应的速度过快经常用控制杆来保持爆裂规律。

第三课1）Some of the energy we can use is called renewable energy。

Renewable energy sources include solar energy, which comes from the sun and can be turned into electricity and heat。

Wind, geothermal energy from inside the earth, biomass from plants, and hydropower and ocean energy from water are also renewable energy sources.。

These types of energy are constantly being renewed or restored.我们使用的一些能源叫做可再生能源。

可再生能源的来源包括来自于太阳并且能够转换成电能和热能的的
太阳能。

风能，来自地球内部的地热能植物的生物能，来自于水的水电能和海洋能都是可再生能源。

这些类型的能源能够不断的更新和恢
复。

2）For example, solar thermal energy involving the collection of solar rays through collectors (often times huge mirrors) need large tracts of land as a collection site。

This impacts the natural habitat, meaning the plants and animals that live there。

The environment is also impacted when the buildings, roads, transmission lines and transformers are built。

The fluid most often used with solar thermal electric generation is very toxic and spills can happen. 例如利用收集器来收集太阳能射线产生的太阳热能时需要大片的土地作为收集场地。

之这就影响了动植物生存的自然栖息地。

当修建建筑物、传输线、公路、变压器时环境也将受到破坏。

大多数使用在生产太阳能电力的流体是有剧毒的并且
经常泄露。

3）Producing geothermal electricity from the earth's crust tends to be localized.。

That means facilities have to be built where geothermal energy is abundant。

In the course of geothermal production, steam coming from the ground becomes very caustic at times, causing pipes to corrode and fall apart。

Geothermal power plants sometimes cost a little bit more than a gas-fired power plant because they have to include the cost
to drill. 从地壳成产地热能发电已经趋向于局部化。

就意味着设备必须建立在地热能充足的地方。

再生产地热的反应过程中来自于地表的热能有时具有腐蚀性，可以引起管路的腐蚀或破碎。

地热电站的费用通常比燃
气电站的费用高，因为其中包含钻井的费用。

第五课1)Walking-beam reheating furnace is an important device with lots of energy consumption in steel plants。

It is important to improve the heating quality of slab and reduce the energy consumption as much as possible.。

In current system, the emphasis is often put on the heating quality while the energy saving is seldom taken into account.。

Because of high nonlinearity large time delay large time-constant and various uncertain factors, the modeling and reliable control of a reheating furnace are always challenging problems。

During the past decade，the challenge has attracted considerable attention and a significant progress has been made in the furnace control。

To obtain the requirement of temperature tracing accuracy and develop energy saving technique in the reheating furnace system, advanced control strategies are needed。

In this paper, a model-based predictive control method, multivariable constrained control (MCC), was used。

It treated the furnace as a multi-input-multi-output system and used the predefined temperature trajectories as a priori。

The simulation results show that the strategy is very satisfactory. 在钢厂中步进式加热炉是能量消耗的最主要的设备。

改变板层的加热质量和尽可能的减少能量消耗是重要的。

在现今的系统中，通常把加热质量放在最主要的位置而忽略了能量消耗。

由于高度非线性的大的迟滞和大的时间常数和许多不确定的因素，建模和可控制的加热炉经常要挑战许多问题。

在过去的十年间，这些挑战得到了巨大的关注并且在加热炉中取得了巨大的进步。

在再热炉系统中为了获得所需求的温度跟踪精度和发展节能技术，应该使用高级的约束控制。

在本文中基于模型预测控制方法，多变量约束控制被使用。

这种控制方法把加热炉看作是多输入多输出的系统。

并且预先确定温度精度为给定值。

这种假设结果表
示这种策略是非常令人满意的。

2Multivariable advanced process control (APC) techniques have been gradually accepted in process industries, which pursue high product quality and lower cost, and have increased environmental responsibility。

APC is usually model based and regulates the processes with optimization algorithms 。

In APC, it can usually improve the control of a process significantly by minimizing the variation in the controlled process variables, dealing with interaction among process variables and automatically controlling set-points of PID loops, which would be normally regulated by operators。

In this paper, a new APC-multivariable constraint control (MCC) is proposed for the advanced control of the reheating furnace.。

Its kernel algorithm is derived from model predictive control (MPC), which has been greatly developed in recent 20 years, and has almost become the accepted standard for constrained multivariable control problems in the process industries.。

Here at each sampling time, starting at the current state, an open loop optimal control problem is solved over a finite horizon.。

At the next time step the computation is repeated starting from the new state and over a shifted horizon，leading to a moving
horizon policy。

多变量高级控制技术已经在过程工业中被广泛的接受。

它追求高的产品质量和较低的消耗并已相应的提高了环保的责任感。

APC是基于模型的并用先进算法调整的控制技术。

运用APC可以通过缩小控制过程变量的变化范围、处理过程变量之间的关系并且自动控制PID循环的正常情况下人工控制的设定点来显著地提高的对过程的控制。

在本章中，我们为再热锅炉的高级控制提出了一个新的APC多约束控制系统。

它的核心算法是从MPC控制中派生出来的。

MPC 控制技术在最近20年里得到了极大的发展，并已经成为在过程过程工业中对多变量多约束控制的执行标准。

在每个采样时间内，从当前状态开始，最佳开环控制问题将在有限的范围内被解决。

在下一个时
间步，计算将在优先的范围内从新状态开始重复。

第六课1）In this experiment, the effectiveness of each heat exchanger is at the heart of the decision of which one would be the best choice for a given industrial application.。

The effectiveness of a heat exchanger is the efficiency with which the exchanger transfers heat from the hot stream to the cold stream, or in the case of a cooler, how well a cold stream can cool a hot stream。

It is of great importance because it dictates the requirements of the hot or cold utilities, which can sometimes be quite costly.在实验中，对一个给定的工业应用各种换热器的有效性是决定是否选择该换热器的核心。

换热器的热效率指的是换热器从热流到冷流传热的效率。

或者在叫冷的情况下，如何良好的用一个流冷却一个热流。

热效率是非常重要的，因为它规定热和冷设备的要求，又是这样换热器的成本是非常高的。

2）The effectiveness depends on the rate at which heat is transferred from one fluid to the other。

The heat is transferred by convection from the hot fluid to the tube wall。

It travels through the tube wall by conduction, and then to the cold fluid by convection once again。

The rate at which heat is transferred by convection depends on the heat transfer coefficient, h, of that fluid。

The greater the heat transfer coefficient, the easier the heat moves from one fluid to the other。

For conduction, the ease with which heat is conducted is shown by the thermal conductivity, k, of the material.热效率取决于热量从一种流体转换到其他流体时的流速。

热量以对流的方式从热流体转换到管墙。

以传热的形式流经管墙，再以对流的形式从管墙转换到冷流体。

以对流的方式转换热量的速率取决于流体的对流换热系数h。

换热系数h越大，热量就越容易从一种流体转移到另一种流体。

对于热传导，传热速率取决于管材导热系数k。

3)Heat exchanger effectiveness is also dependent on the nature of the material the exchanger is built out of 。

Some materials conduct heat better than others, so it is essential to have a material with a high thermal conductivity in order to have good transfer of heat from one fluid to the other。

The effectiveness of the heat exchanger is also dependent on the fluids flowing through the tubes.。

The specific heats and the flow rates have a significant effect on the rate of heat transferred, so it is also of interest.换热器的热效率也取决于制造换热器材料的性能。

一些材料的导热性比其他材料要好，所以为了使热量较好的从一种流体转换到另一种流体，有必要选择一种高导热性的材料。

换热器的热效率也取决于流经管道的流体。

流体的比热和流速对于传热的速率有
很重要的影响，所以流体的性质也很重要。

第七课1)There are, however, two major aspects of fluid mechanics which differ from solid-body mechanics。

The first is the nature and properties of the fluid itself, which are very different from those of a solid。

The second is that, instead of dealing with individual bodies or elements of known mass, we are frequently concerned with the behavior of a continuous stream of fluid, without beginning or end.然而，流体力学区别于固体力学有两个重要的方面。

这第一个方面是流体本身不同于固体的性质和属性。

第二个区别，流体力学通常涉及到的是无始终的连续
的流束的性质，而不是处理以知质量的单个单元。

2)Knowledge and understanding of the basic principles and concepts of fluid mechanics are essential in the analysis and design of any system in which a fluid is the working medium.。

Many applications of fluid mechanics make it one of the most vital and fundamental of all engineering and applied scientific studies。

The flow of fluids in pipe and channels makes fluid mechanics importance to civil engineers。

The study of fluid machinery such as pumps, fans, blowers, compressors turbines, heat exchangers, jet and rocket engines, and the like, makes fluid mechanics of importance to mechanical engineers。

Lubrication is an area of considerable importance in fluid mechanics。

The flow of air over objects, aerodynamics, is of fundamental interest to aeronautical and space engineers in the design of aircraft, missiles and rockets.。

In meteorology,
hydrology and oceanography the study of fluids is basic since the atmosphere and the ocean are fluids. And today in modem engineering many new disciplines combine fluid mechanic with classical disciplines.。

For example, fluid mechanics and electromagnetic theory are studied together as magnetogasdynamics, in new types of energy conversion devices and in the study of stellar and ionospheric phenomena, magnetogasdynamics is vital.在分析和设计以流体为工作介质的系统中流体力学的知识和基本理念和概念的理解是非常重要的。

许多流体力学的应用使它成为在所有的工程和应用科学研究的至关重要和最基础的。

在运输管道中流体流动使得流体力学成为民用建筑的重要部分。

流体机械的研究像泵、风扇、吹风机、压缩式涡轮机、换热器、喷射器和火箭引擎等等都是的流体力学成为机械工程重要的部分。

在流体力学中润滑是很重要的领域。

空气中物体的流动，空气动力学，是航空航天工程师在设计飞机、导弹、和火箭发射的基本利益。

在气象学、水文学、海洋学、流体的研究是基本，即使大气和海洋都是流体。

现今，在现代工程中许多新的学科是流体力学和古典学科的结合。

例如，流体力学和电磁理论一起作为磁气体力学来研究，在新类型的能量转换的研究设备以及恒星和电离层的现象的研究中磁气体力学
动力学是至关重要的。

3)On the contrary, the collapse of the Tacoma Narrows Bridge
in U.S.A. is evidence of the possible consequences of neglecting the basic principles of fluid mechanics.。

On a memorable day in November 1940, Nature decided to teach us all a lesson.。

The wind could not even be considered strong on that
day, but it happened to disturb the great Tacoma Narrows suspension bridge cyclically with a frequency close to the bridge’s natural frequency of vibration。

The entire bridge started to dance.。

Traffic was stopped; and an astonished public watched the bridge dance itself to pieces.相反的是，美国塔克马大桥的倒塌就是忽视流体机械基本原则的一个可能后果的证据。

在1940年纪念日那一天，自然决定给我们一个教训。

那天的风甚至称不上大，但却碰巧破坏了壮观的塔克马悬索桥仅仅是因为风的频率而引起的共振。

整个大桥开颤动。

交通被禁止，很多震惊的群众看到了
大桥把自己震动解体成碎片。

第八课1）Most gas-turbine engines (Fig.3.11)include at 1east a compressor, a combustion chamber, and a turbine.。

These are usually mounted as an integral unit and operate as a complete
prime mover on a so-called open cycle where air is drawn in from the atmosphere and the products of combustion are finally discharged again to the atmosphere。

Since successful operation depends on the integration of all components, it is important to consider the whole device, which is actually an internal-combustion engine, rather than the turbine alone.大多数的汽轮机像表3.11都至少包括一个压缩机、一个燃烧室和一个涡轮机。

这些通常都是安装作为一个整体的单位而操作是一个彻底的原动机所谓开始循环而空气从大气中绘制燃烧产物最终又排放到大气中。

因为成功的操作取决于这些元件的组合，他对整个装置的考虑是非常重要的，这实际上是一个内燃机而不是单纯的汽轮机。

2）Gas turbines were developed primarily for aircraft industry and for internal combustion engine supercharges, now they have played a unique role in electric utility systems.。

Because of their relatively low initial cost, compactness and quick starting(they can be on the line at rated load within 30 minutes), the plants are suitable for emergency service and “peaking” service during daily periods of high load demand.燃气轮机主要用于飞机制造业和内燃机的增压，现在在电业系统中扮演一个独一无二的角色。

由于他们相对低的初始成本紧凑性和启动速度（他们能够额定载荷线在30分钟内完成）这些装置适用于在日常
高负荷要求的周期下紧急情况维修和峰值维修。

3）Gas turbine plants operate on the Brayton cycle.。

The operating principle of gas turbine is basically as follows: ambient air is drawn into a multistage compressor and is compressed to about 10 times atmospheric pressure。

The compressed air then passes through the combustion chamber where the preheated fuel is injected and burned.。

The products of combustion enter the turbine and expand to approximately atmosphere pressure.。

The turbine section powers both the
generator and compressor. 燃气轮机装置操作是一个布雷顿循环。

燃气轮机的工作原理主要是这样的：环境中的空气被一个多级压缩机吸收然后被压缩到十倍大气压。

压缩的气体进入到燃烧室，在这里预热的燃料被喷射和燃烧。

燃烧产物进入到汽轮机后膨胀到接近大气压。

汽轮机的部分驱动有发电
机和压缩机。

4）About two-thirds of the turbine output is used to drive the compressor while the remainder is for power generation。

This
arrangement is called the simple cycle gas turbine, which is characterized, by large exhaust energy loss.。

In general, the simple-cycle gas turbine has relatively low efficiency(25 to 30%)as compared with coal-fired steam turbine system.。

The efficiency of simple cycle can be increased by installing a recuperator or waste heat boiler to the turbine's exhaust part.。

A recuperator captures waste heat in the turbine exhaust stream to preheat the compressor discharge air before it enters the combustion chamber。

A waste heat boiler generates steam by capturing heat form the turbine exhaust.。

These boilers are known as heat recovery steam generators (HRSG)。

They can provide steam for heating or industrial processes, which is called cogeneration.。

High-pressure steam from these boilers can also generate power with steam turbines, which is called a combined cycle (steam and combustion turbine operation).。

Recuperators and HRSGs can increase the gas turbine's overall energy cycle efficiency up to 80%.。

The combined-cycle plant is shown in Fig 3.12。

大约三分之二的汽轮机的输出被用于驱动压缩机然而剩余的部分用来发电。

这个布置叫做简单循环燃气轮机，以大量的排气和能量损失为特征。

总的来说，和燃煤汽轮机相比简单循环燃气轮机有相对低的热效率。

低的循环效率可以通过在汽轮机尾部安装一个回热式换热器或一个废热锅炉来提高。

一个恢复装置捕获废热在汽轮机排流预热之前使空气排出进入燃烧室。

一个废热锅炉产生的蒸汽扑火热量形成汽轮机的驱动力。

这样的锅炉叫做回热式蒸汽锅炉。

它们可以提供蒸汽用来加热和工业生产，这种方式叫做热电联产。

从这些锅炉中出来的高压蒸汽也可以用于蒸汽轮机发电，这种叫做组合式循环。

回热式换热器和回热蒸汽锅炉可以使燃气轮机全部热量循
环效率提升80% 。

这个联合循环装置见图3.12 第十章1）In fire tube boilers, the combustion gases pass inside boiler tubes, and heat is transferred to water on the shell side.。

Scotch marine boilers are the most common type of industrial fire tube boiler。

The Scotch marine boiler is an industry workhorse due to low initial cost, and advantages in efficiency and durability.。

Scotch marine boilers are typically cylindrical shells with horizontal tubes configured such that the exhaust gases pass through these tubes, transferring energy to boiler water on the shell side.在火管锅炉里，燃烧气体在锅炉管道中通过，热量在壳程内传给了。

苏格兰式船用锅炉是应用最广
泛的典型工业火管锅炉。

由于低的最初花费，在效率和耐久性的优势，苏格兰式船用锅炉是工业的重负荷机器。

苏格兰式船用锅炉是一种典型的配置有水平管道的圆柱形壳体，因此排出的气体通过这些管子，
在壳体侧面把能量转移给锅炉中的水。

2）Scotch marine boilers contain relatively large amounts of water, which enables them to respond to load changes with relatively little change in pressure.。

However, since the boiler typically holds a large water mass, it requires more time to initiate steaming and more time to accommodate changes in steam pressure.。

Also, Scotch marine boilers generate steam on the shell side, which has a large surface area, limiting the amount of pressure they can generate。

In general, Scotch marine boilers are not used where pressures above 300 psig are required.。

Today, the biggest fire tube boilers are over 1,500 boiler horsepower.苏格兰式船用锅炉含有相当多的水，这使得它们能够在压力变动很小的情况下应对较大的负荷变化。

然而，由于锅炉含水质量很大，初始化蒸气和适应蒸汽压力变化的时间较长。

并且，苏格兰船用锅炉在壳程产生蒸汽，壳程有很大的表面积，这限制了它所产生的蒸汽的压力。

总的来说，当需用压力高于300psig的时候，苏格兰船用锅炉就不被应用了。

当今，最大的火管锅炉已超过1500
锅炉马力。

3）Fire tube boilers are often characterized by their number of passes, referring to the number of times the combustion (or flue) gases flow the length of the pressure vessel as they transfer heat to the water。

Each pass sends the flue gases through the tubes in the opposite direction.。

To make another pass, the gases turn 180 degrees and pass back through the shell.。

The turnaround zones can be either dry-back or water-back.。

In dry-back designs, the turnaround area is refractory lined.。

In water-back designs, this turnaround zone is water-cooled, eliminating the need for the refractory lining.火管锅炉的特点就是它的管程数，程数指的是当烟气与水换热时流过压力导管长度的次数。

每一程燃烧气体都以相反的方向流过导管。

为了实现下一程，气体转过180°，重新流过管程。

气体转弯的区域可以是干背或者湿背的。

在干背式设计下，转弯区域是耐火衬里的。

在湿背设计下，转弯区域是水冷的，消除了对耐火衬里的需要。

4)In water tube boilers, boiler water passes through the tubes while the exhaust gases remain in the shell side, passing over
the tube surfaces.。

Since tubes can typically withstand higher internal pressure than the large chamber shell in a fire tube, water tube boilers are used where high steam pressures (as high as 3,000 psig) are required.在水管锅炉里，锅炉水经过管时废气仍然保持在通过管的表面壳的一面。

由于管道通常比大的火罐壳室承受比较高的内部压力，在高压蒸气被要求时，水管锅炉被应用。

5)Water tube boilers are also capable of high efficiencies and can generate saturated or superheated steam。

The ability of water tube boilers to generate superheated steam makes these boilers particularly attractive in applications that require dry, high-pressure, high-energy steam, including steam turbine power generation. 水管锅炉通常具有较高的效率并且能够产生过热蒸汽。

水管锅炉具有产生过热蒸汽的能力使得这些锅炉在需要干的、高压的、高能的蒸汽，包括汽轮机发电机组的应用方面有很强烈
的吸引。

6)The performance characteristics of water tube boilers make
them highly favorable in process industries, including chemical manufacturing, pulp and paper manufacturing, and refining.。

Although fire tube boilers account for the majority of boiler sales in terms of units, water-tube boilers account for the majority of boiler capacity.水管锅炉的性能特征使得它们在过程工业方面有很好的应用，包括化工制造业、造纸厂和精炼方面。

虽然火管锅炉在单位方面所占有大多数的销售额，但是水管锅炉
在锅炉容量上占有较大比例。

第十一章1)The most common source of corrosion in boiler systems is dissolved gas: oxygen, carbon dioxide and ammonia.。

Of these, oxygen is the most aggressive.。

The importance of eliminating oxygen as a source of pitting and iron deposition cannot be over-emphasized.。

Even small concentrations of this gas can cause serious corrosion problems.在锅炉系统中，腐蚀的常见的主要来源是不溶性气体：氧气、二氧化碳、氨气。

在这些气体中，氧气是最强烈的。

在怎么重视消除氧气铁的点蚀和沉积的来源的重要性，也不为过。

即使是少量的这种气体也能引起严重的腐蚀问题。

2)One of the most serious aspects of oxygen corrosion is that
it occurs as pitting。

This type of corrosion can produce failures even though only a relatively small amount of metal has been lost and the overall corrosion rate is relatively low.。

The degree of oxygen attack depends on the concentration of
dissolved oxygen, the pH and the temperature of the water.氧化腐蚀最为严重的一方面是它将产生点。

这种类型的腐蚀即使是只有相对少量的金属损失和相对较低的腐蚀率也能产生破坏性。

氧化腐
蚀的程度取决于溶解氧的浓度、ph值和水温。

3)The influence of temperature on the corrosivity of dissolved
oxygen is particularly important in closed heaters and economizers where the water temperature increases rapidly。

Elevated temperature in itself does not cause corrosion。

Small concentrations of oxygen at elevated temperatures do cause severe problems。

This temperature rise provides the driving force that accelerates the reaction so that even small quantities of dissolved oxygen can cause serious corrosion.溶解氧的腐蚀性对于温度的影响是相当重要的，尤其是水温迅速增长的加热器和省煤器。

升高温度本身是不能引起腐蚀的。

低浓度的氧气在升高温度时也会造成严重的问题。

温度的升高对加速反应提供了驱动力，因此，即便是很少量的溶解氧也可以造成严重的腐蚀。

第十二课1)Many residential heating systems consist of a stove, a heat pump, or an electric resistance heater, The air in these systems is heated by circulating it through a duct that contains the tubing for the hot gases or the electric resistance wires, as shown in Fig 3.19.。

The amount or moisture in the air remains constant during this process since no moisture is added to or removed from the air.。

That is, the specific humidity of the air remains constant(ω=constant) during a heating(or cooling) process with no humidification or dehumidification.。

Such a heating process will proceed in the direction of increasing dry-bulb temperature following a line of constant specific humidity on the psychrometric chart, which appears as a horizontal line.许多民用加热系统是由一个炉子、一个热泵、电阻加热器组成的这些系统中的空气是通过一个含有管材热气体和电阻线的管子来进行循环加热的如图3.19所示。

在这个过程中空气中分子量是保持不变的即没有分子的增加也没有从空气中的转移。

这样在加热过程中空气的相对湿度保持不变即没有加湿也没有除湿。

这样的加热过程是在恒定的相对湿度线上干球温度增加的方向上进行的，这
条线在温湿图上显示的是一条水平直线。

2)Notice that the relative humidity of air decreases during a
heating process even if the specific humidity ω remains
constant。

This is because the relative humidity is the ratio of the moisture content to the moisture capacity of air at the same temperature, and moisture capacity increases with temperature.。

Therefore, the relative humidity of heated air may be well below comfortable levels, causing dry skin, respiratory difficulties, and an increase in static electricity.注意到即使在相对湿度保持恒定的情况下在加热过程中空气的相对湿度也是减少的。

这是因为相对湿度是在相同的温度下含水量和含水能力的比值，含水能力随温度的而增加。

因此，加热空气的相对湿度远低于舒适水平，也就引起皮肤干燥，呼吸困难、和增
加静电。

3)A cooling process at constant specific humidity is similar to the heating process discussed above, except the dry-bulb temperature decreases and the relative humidity increases during such a process, as shown in Fig.3.20.。

Cooling can be accomplished by passing the air over some coils through which a refrigerant or chilled water flows.除了在冷却过程中有干球温度减少和相对湿度增加的情况下，在恒定的相对湿度下冷却过程和上文讨论的加热过程相似，如图3.20所示。

冷却过程可以经过线
圈上空气被冷却液后冷却水冷却来完成。

第十三课1)Two fluids, of different starting temperatures, flow through the heat exchanger。

One flows through the tubes (the tube side) and the other flows outside the tubes but inside the shell (the shell side).。

Heat is transferred from one fluid to the other through the tube walls, either from tube side to shell side or vice versa.。

The fluids can be either liquids or gases on either the shell or the tube side.。

In order to transfer heat efficiently, a large heat transfer area should be used, so there are many tubes. In this way, waste heat can be put to use.。

This is a great way to conserve energy.不同初始温度的流体流经换热器一种流经管程、一种流经壳程。

热量经过管壁有一种流体传递到另一种流体，即从管程到壳程。

在壳程和管程中流体既可以是液体也可以是气体。

为了有效地传热这就需要大片的传热区域所以就需要许多的管，用这种方法，废热也能被使用。

这是一种高效的节能方
法2)Heat exchangers with only one phase (liquid or gas) on each side can be called one-phase or single-phase heat exchangers.。

Two-phase heat exchangers can be used to heat a liquid to boil
it into a gas (vapor), sometimes called boilers, or cool a vapor to condense it into a liquid (called condensers), with the phase change usually occurring on the shell side.。

Boilers in steam engine locomotives are typically large, usually cylindrically-shaped shell-and-tube heat exchangers.。

In large power plants with steam-driven turbines, shell-and-tube condensers are used to condense the exhaust steam exiting the turbine into condensate water which can be recycled back to be turned into steam, possibly into a shell-and-tube type boiler.在每一侧只有一种状态的物质（气态或液态）的换热器称为单项换热器。

双项换热器可以应用于一种液体使之汽化程气态。

这时这种换热器被称作锅炉或是冷凝蒸汽使之成为液体，这种相变通常发生在壳程。

在蒸汽火车上的锅炉通常是大型的、圆柱形的管式换热器在有蒸汽驱动汽轮机的大型电厂中管壳式冷凝器用于把从汽轮机出来的废气冷凝成水，冷凝水可以再次循环变成蒸汽，进入管壳式锅炉中。

3)To be able to transfer heat well, the tube material should have good thermal conductivity。

Because heat is transferred from a hot to a cold side through the tubes, there is a temperature difference through the width of the tubes.。

Because of the tendency of the tube material to thermally expand differently at various temperatures, thermal stresses occur during operation.。

This is in addition to any stress from high pressures from the fluids themselves.。

The tube material also should be compatible with both the shell and tube side fluids for long periods under the operating conditions (temperatures, pressures, pH, etc.) to minimize deterioration such as corrosion.。

All of these requirements call for careful
selection of strong, thermally-conductive, corrosion-resistant, high quality tube materials, typically metals。

Poor choice of tube material could result in a leak through a tube between the shell and tube sides causing fluid cross-contamination and possibly loss of pressure.为了能够较好的传热，管子的材料应该有较好的导热性能。

因为热量是经过管子从热的一面传到冷的一面，在管子的厚度方向存在着温差。

由于在不同的温度下管子的热膨胀趋势不同，在运行的过程中产生热应力，加上由于流体本身在高压下产生的应力，为了使腐蚀这样的破坏达到最小管子的材料应该在运行的状态下长期同管程和壳程流体相适应。

A 这些所有的要求都要认真的选择坚固的、热性能好的、耐腐蚀性的、。