在冷干机蒸发压缩式制冷系统中，蒸发器、压缩机、节流机构和冷凝器是不可或缺的组成部分，统称制冷系统四大件。其作用如下：
Evaporator, compressor, throttling mechanism and condenser are indispensable components in evaporative compression refrigeration system of cold drying machine. They are generally referred to as four parts of refrigeration system. The following functions are as follows:
1.蒸发器：蒸发器是一个换热设备，制冷剂液体在蒸发器里吸热汽化，在此过程中对其周围的环境产生制冷效应。制冷剂在蒸发器里汽化过程是等压下的沸腾过程，沸腾温度是该压力下的饱和温度，即沸点。因此，把蒸发器称为“沸腾器”更为确切，但制冷工程中习惯上都称为蒸发器。蒸发器内制冷剂沸腾的压力称为蒸发压。力P0,相对应的饱和温度（沸点）称为蒸发温度t0，沸腾汽化过程称为蒸发过程。
1. evaporator: the evaporator is a heat exchange equipment. The refrigerant liquid is heated and vaporized in the evaporator. In this process, the cooling effect is produced to the environment around it. The vaporization process of the refrigerant in the evaporator is the boiling process under the constant pressure, and the boiling temperature is the saturation temperature under the pressure, that is, the boiling point. Therefore, it is more accurate to call the evaporator "the boiling device", but it is commonly known as the evaporator in the refrigeration engineering. The pressure of the boiling of the refrigerant in the evaporator is called the evaporation pressure. Force P0, the corresponding saturation temperature (boiling point) is called the evaporation temperature T0, and the boiling vaporization process is called evaporation process.
2.压缩机：压缩机是从蒸发器中抽吸出制冷剂蒸汽并对其进行压缩的设备。它的功能有：
2. compressor: the compressor is the equipment that draws out the refrigerant steam from the evaporator and compresses it. Its functions are:
（1）从蒸发器中抽吸出制冷剂蒸汽以维持蒸发器内一定的压力，同时也就维持了一定的蒸发温度；
(1) draw out the refrigerant steam from the evaporator in order to maintain a certain pressure in the evaporator, and also maintain a certain evaporation temperature.
（2）将吸入的制冷剂蒸汽进行压缩，或是说将蒸汽压力提高，从而有可能在较高温度下将它冷凝成液体，使制冷剂得到重复使用；
(2) to compress the inhaled refrigerant vapor, or to increase the vapor pressure, so that it can be condensed into liquid at higher temperature, so that refrigerants can be reused.
（3）在制冷系统中起输送制冷剂的作用。
(3) play the role of refrigerant in the refrigeration system.
3.冷凝器：冷凝器是一个换热设备，制冷剂在其内凝结并释放出热量，这些热量由空气或水带走。冷凝器中用于冷却制冷剂蒸发并带走凝结时放出的热量的介质称为“冷却剂”或“冷却介质”，对于水就称为冷却水。冷凝器中的冷凝过程是等压过程，其中制冷剂压力称为冷凝压力pk，，对应的饱和温度称为冷凝温度tk。
3. condenser: condenser is a heat exchanger that condenses and releases heat in it, which is taken away by air or water. In the condenser, the medium used to cool the refrigerant evaporation and carry out the heat released during condensation is called coolant or cooling medium. For water, it is called cooling water. The condensation process in the condenser is an isobaric process, in which the refrigerant pressure is called the condensation pressure PK, and the corresponding saturation temperature is called the condensation temperature TK.
4.节流机构：节流机构的功能有：
4. throttle mechanism: the function of the throttle mechanism is:
（1）使冷凝压力（高压）下的冷凝剂液体转变成蒸发压力（低压）下的冷凝液体，为制冷剂创造低压低温下汽化的条件；
(1) the condensing liquid under condensation pressure (high pressure) is changed into condensed liquid under evaporating pressure (low pressure), which creates conditions for refrigerant to vaporize at low pressure and low temperature.
（2）调节注入蒸发器的制冷剂液体供给量。
(2) adjust the supply of refrigerant liquid in the injection evaporator.
节流机构可以是自动或手动的节流阀（又称膨胀阀）或毛细管。
A throttle mechanism can be an automatic or manual throttle valve (also known as an expansion valve) or a capillary.
冷冻式干燥机制冷系统必须有四大部件──蒸发器、压缩机、冷凝器和节流机构，缺一不可。当然，一个实际的制冷系统远不止上述四个部件，还有阀门和其他一些辅助设备和机构，以保证系统安全、可靠、高效的运行。
The refrigeration system must have four parts - evaporator, compressor, condenser and throttle mechanism. Of course, a practical refrigeration system is much more than the above four parts, as well as valves and other auxiliary devices and institutions, so as to ensure the safe, reliable and efficient operation of the system.
