Both refrigerated dryer and desiccant air dryer are indispensable parts of compressed air systems. Desiccant regenerative dryers are simple in structure. But the refrigerant air dryer is different. Refrigerated air dryer contains many spare parts. Moreover, refrigerant dryers are divided into air-cooled and water-cooled type. Their spare parts are a little different. Now we will introduce the functions of each refrigerated air dryer parts. 
1.Refrigeration compressor
The refrigeration compressor is the heart of the refrigeration system. It’s also the key part of refrigerated air dryer. Without it, the entire system would have no source of power. The function of compressor is mainly to raise the refrigerant from low pressure to high pressure. And keeps it in constant circulation. It allows the refrigerant dryer system to continuously discharge the heat inside.
Therefore, the quality of the refrigerant compressor affects the cooling efficiency of the refrigerated dryer. It also affects the stability of the dryer. And our refrigerant dryers use the best brands compressors, such as Panasonic, Copeland and Danfoss. They have very good refrigeration effect. Also the quality is reliable. 
2. Condenser
The function of the condenser is mainly take the conversion for the refrigerant. The compressor discharges the high-pressure and super-heated refrigerant vapor. The condenser then cools it. Finally it turns into liquid refrigerant. This keeps the refrigeration process circulating.
There are 2 types of condensers, namely air-cooled and water-cooled. The air-cooled condenser uses air as the cooling medium. The refrigerant is condensed inside the tube. Air flows outside the tube. The air absorbs the heat released from the refrigerant vapor inside the tube. Because the heat transfer coefficient of air is small, the outside of the tube is often with ribs. So as to strengthen the heat transfer outside the tube. The water-cooled condenser uses water as the cooling medium. It carries away the heat released when the refrigerant condenses. The cooling water can be used once. It can also be recycled. If want to use the circulating water, there must be a cooling tower. Ensure that the water is constantly cooled.
The former consender parts are mainly suitable for small refrigerated air dryer. It is also used in places where water is not very abundant. But it is more affected by the ambient temperature. And the latter needs to have sufficient water source. Its cooling effect is better than the former. Besides, it is not affected by the ambient temperature. Many large refrigerant dryers are water-cooled type.
3. Evaporator
The evaporator is the main heat exchange part of refrigerated air dryer. The compressed air will be forced to cool in the evaporator. Some of the water vapor in it cools and condenses. Then it becomes liquid water. Eventually it will be removed, thus drying the air. At the same time, the refrigerant absorbs heat from the surrounding area during this process. Thus, it als reduce the temperature of the air.
In order to obtain the best possible heat exchange effect, it is necessary to increase the heat exchange area of the compressed air side. Therefore, the outer edge of the evaporator copper tube of the refrigerant dryer covered with fins is to increase the area of heat exchange. 
4. Heat exchanger or pre-cooler
The heat exchanger is a part to exchange heat between air and air. In a refrigerated dryer, its main function is as follows: on the one hand, it recovers the cold energy carried in the air after being cooled by the evaporator. On the other hand, use this part of the cold energy to cool the saturated compressed air. So as to reduce the heat load of the refrigeration system of the dryer. It can achieve the purpose of energy saving.
In fact, the role of heat exchanger is mainly energy saving. So, in some refrigerant air dryers, there are no heat exchangers. It is still possible to continue to run. Only the consumption of energy is relatively larger. If there is no pre-cooler part, the refrigerant air dryer is the normal temperature type. The inlet temperature should not be too high, i.e. not more than 45℃. If there is a pre-cooler, it is a high temperature type refrigerated air dryer. The inlet air temperature can be as high as 80℃.
In addition, after refrigeration, the compressed air temperature is low. The pre-cooler can make its temperature get back up. So it avoids the phenomenon of “hanging dew” outside the tube due to low temperature. It improves the workshop environment.
5. Thermal expansion valve
The thermal expansion valve is the throttling part in the refrigeration system. During the operation of the refrigerant dryer, the supply and regulation of the evaporator refrigerant is realized through it.
The expansion valve can make the liquid refrigerant to become wet vapor. Then the refrigerant absorbs heat in the evaporator. This results in a cooling effect. It has a temperature sensor. When the load changes, the thermal expansion valve can detect the compressor suction super-heat temperature. Thus, it adjusts the valve spool opening degree. Finally controls the refrigerant supply into the evaporator. So it can prevent the liquid refrigerant from flowing into the compressor and generating liquid strike phenomenon. 
6. Hot gas bypass valve
It is also important refrigerated air dryer parts. The evaporator cools the compressed air . There will be a large amount of condensate precipitation. If the refrigerant evaporation temperature is too low, the condensate will freeze in the evaporator. Severe icing will make the airflow channel blocking. Eventually, the compression system will not deliver air properly.
To prevent this situation, we must control and adjust the refrigerant evaporation temperature. Therefore, adding a hot gas bypass valve between the condenser and evaporator is the easiest and most effective way. When the evaporating pressure is lower than the range of the detection instrument, the hot gas bypass valve will open automatically. The high temperature refrigerant vapor in the condenser will then enter the evaporator directly. This raises the evaporation temperature. Thus, it can avoid the phenomenon of icing blockage. 
7. High and low voltage protection switch
They makes the compressor have its own protection function. It prevents the compressor motor from burning out. When the compressor discharge pressure exceeds the set value, the pressure control switch automatically cuts off the circuit. Make the compressor stall. Thus playing a safety protection role. When the suction pressure is lower than the set value, the role is the same. In general, high pressure setting value is 2.5Mpa. And low pressure setting value is 0.2Mpa.
Above are the functions of the seven main parts of the refrigerated air dryer.