化工原理(下册)简答题整理【中英双语】

干燥对于不饱和空气：t>tw=tas>td For unsaturated air对于饱和空气：t=tw=tas=td For saturated air除湿的方法：1.机械分离法：通过压榨、过滤、离心分离等方法除湿，能耗较少，比较经济，但除湿不完全。

2.吸附脱水法：用固体吸附剂，如：氯化钙等，吸去物料中含有的水分，这种方法去除的水分量很少，而且成本较高。

3.干燥法：利用热能使湿物料中的湿分通过汽化除去，能耗较大，一般采用先机械分离法，再干燥法。

Dehumidification methods: 1. Mechanical separation method: dehumidification by pressing, filtering, centrifugal separation, etc., with less energy consumption and relatively economic, but not complete dehumidification. 2. Adsorption dehydration method: use solid adsorbent, such as calcium chloride, etc., to absorb the water contained in the material. The water removed by this method is very small, and the cost is high. 3. Drying method: the heat energy is used to remove the moisture in the wet material by vaporization, and the energy consumption is large. Generally, the mechanical separation method is used first, and then the drying method is used.干燥法的种类：1.传导干燥：热能通过传热壁面以传导方式传给物料，产生的湿分蒸汽被气相带走。

2.对流干燥：干燥介质直接与湿物料接触，热能以对流方式传给物料，产生的蒸汽被干燥介质带走。

这是传热和传质同时进行的过程。

3.辐射干燥：由辐射器产生的辐射能以电磁波的形式到达物料表面，被物料吸收而变为热能，从而使湿分汽化。

4.介电加热干燥：将物料置于高频电场中，电能在潮湿的电介质中转变为热能，使液体升温汽化，加热过程发生在物料内部，速率较快。

Type of drying method: 1. Conduction drying: the heat energy is transmitted to the material through the heat transfer wall in the form of conduction, and the wet steam generated is taken away by the gas phase. 2. Convection drying: the drying medium directly contacts with the wet material, the heat energy is transferred to the material by convection, and the steam generated is taken away by the drying medium. This is a simultaneous process of heat and mass transfer. 3. Radiation drying: the radiation energy generated by theradiator reaches the surface of the material in the form of electromagnetic wave, which is absorbed by the material and converted into heat energy, so as to vaporize the moisture. 4. Dielectric heating and drying: the material is placed in a high-frequency electric field, and the electric energy is converted into heat energy in the wet dielectric, so that the liquid is heated and vaporized. The heating process takes place in the material, and the speed is fast.露点温度：不饱和湿空气冷却至刚好达到饱和的温度。

干球温度：空气的真实温度。

湿球温度：感温球在有水湿润的状态下测取的温度，热、质交换过程进行到空气传给湿润表面的显热等于水分汽化所需的汽化热为止，此时温度稳定。

湿空气温度一定，湿度越高，湿球温度也越高。

干球温度越高，湿球温度也越高。

湿球温度受空气温度和湿度的影响，当空气达到饱和时，湿球温度等于干球温度。

绝热饱和温度：热、质交换进行无限长时间，则空气将达到饱和状态，此时气相和液相达到同一温度，就是绝热饱和温度。

Dew point temperature: the unsaturated wet air is cooled to just reach the temperature of saturation.Dry bulb temperature: the true temperature of the air.Wet bulb temperature: the temperature measured by the temperature sensing bulb when it is wet with water. The heat and mass exchange process lasts until the sensible heat transmitted by air to the wet surface is equal to the vaporization heat required by the water vaporization. At this time, the temperature is stable. The higher the humidity is, the higher the wet bulb temperature is. The higher the dry bulb temperature is, the higher the wet bulb temperature is. The wet bulb temperature is affected by the air temperature and humidity. When the air reaches saturation, the wet bulb temperature is equal to the dry bulb temperature.Adiabatic saturation temperature: if the heat and mass exchange is carried out for an infinite period of time, the air will reach the saturation state. At this time, the gas phase and the liquid phase will reach the same temperature, which is the adiabatic saturation temperature.平衡水分：湿物料在一定的空气状态下干燥的极限。

自由水分：物料中的含水量超过平衡含水量的那部分水分。

结合水：蒸气压低于纯水蒸气压的水分。

非结合水：游离在固体表面的水分。

这种水分的蒸气压与同温度下普通水的蒸气压一样。

Equilibrium moisture: the limit of drying wet materials under certain air conditions.Free moisture: the moisture content in the material that exceeds the equilibrium moisture content.Combined water: water whose vapor pressure is lower than that of pure water.Unbound water: water free on the surface of a solid. The vapor pressure of this water is the same as that of ordinary water at the same temperature.预热阶段：物料温度变为空气的湿球温度，含水量减少。

恒速干燥阶段：物料维持在湿球温度，水分在物料表面的存在形式是连续水膜。

空气传给物料热量，物料再传给表面的水分，用于水分的汽化，过程与纯水汽化过程机理相同。

干燥速率是常数。

移去的是非结合水。

降速干燥阶段：1.物料表面水膜开始逐渐消失，水分汽化逐渐进入物料的内部，去除的是部分非结合水和部分结合水。

空气将热能传给物料表面，再通过物料表面向内部传递，水蒸气部分是表面水直接汽化，部分是从物料内部向表面迁移。

2.物料表面全部变为干区，不再有液体水分，热、质传递传递阻力主要在物料内部，此时去除的水分全部是结合水。

（传热、传质快慢主要取决于物料内部结构特性）Preheating stage: the material temperature changes to the wet bulb temperature of air, and the water content decreases.Constant speed drying stage: the material is kept at the wet bulb temperature, and the existence form of water on the material surface is continuous water film. The air transfers heat to the material, and the material transfers water to the surface, which is used for water vaporization. The process mechanism is the same as that of pure water vaporization. The drying rate is constant. The removed water is unbound water.The stage of drying at reduced speed: 1. The water film on the surface of the materialbegan to disappear gradually, and the water vaporized gradually into the interior of the material, removing part of the non combined water and part of the combined water. Air transfers heat energy to the surface of the material, and then transfers it to the interior through the surface of the material. Part of the water vapor is directly vaporized by the surface water, and part of it is transferred from the interior of the material to the surface. 2. The surface of the material becomes dry area, and there is no liquid water. The resistance of heat and mass transfer is mainly inside the material. At this time, all the water removed is combined water.(the speed of heat and mass transfer mainly depends on the internal structure characteristics of the material)恒定干燥条件：干燥介质的状态（湿度、焓等）及其流速，干燥介质与物料的接触方式不变。