1. The role of refrigeration compressors Refrigeration compressors are the most important equipment in refrigeration equipment, and are often referred to as the host in refrigeration equipment. The increase of refrigerant vapor from low pressure to high pressure and the continuous flow and transportation of vapor are all accomplished by the work of refrigeration compressors.
In other words, the role of the refrigeration compressor is:
1) Absorb refrigerant vapor from the evaporator to ensure a certain evaporation pressure in the evaporator.
2) Increase the pressure and compress the low-pressure and low-temperature refrigerant vapors into high-pressure and high-temperature superheated vapors to create conditions for condensation at higher temperatures (such as summer temperatures around 35 ° C).
3) Send and push the refrigerant to flow in the system to complete the refrigeration cycle.
2. Depending on the type of cooling medium, condensers can be classified into four categories, and their functions are as follows:
⑴Water cooling type: In this type of condenser, the heat released by the refrigerant is taken away by the cooling water. The cooling water can be used once or recycled. Water-cooled condensers can be divided into vertical shell and tube type, horizontal shell and tube type and sleeve type according to their different structural types.
⑵Air-cooled (also called air-cooled): In this type of condenser, the heat emitted by the refrigerant is taken away by the air. The air can be natural convection, or forced flow using a fan. This type of condenser is used in Freon refrigeration installations where water supply is difficult or difficult.
⑶ Water-air cooling type: In this type of condenser, the refrigerant is cooled by water and air at the same time, but it mainly depends on the evaporation of the cooling water on the surface of the heat transfer tube, and absorbs a large amount of heat from the refrigerant side as water. Latent heat of vaporization, the role of air is mainly to remove water vapor in order to accelerate the evaporation of water. Therefore, this type of condenser consumes very little water. It is the preferred type of condenser for areas with dry air, low water quality, and low water temperature. This type of condenser can be divided into two types, evaporative type and irrigating type, according to their structural types.
⑷Evaporation-condensation: In this type of condenser, the cooling effect of the refrigerant evaporation in another refrigeration system is used to cool the refrigerant vapor on the other side of the heat transfer partition, which promotes the latter to condense and liquefy. Such as the evaporator-condenser in the cascade refrigerator.
3. The role of the expansion valve: The expansion valve plays the role of throttling and reducing the pressure. When the high-pressure refrigerant liquid condensed by the condenser passes through the throttle valve, the pressure drops due to the obstruction, which causes part of the refrigerant liquid to vaporize and absorb The latent heat of gasification also reduces its temperature accordingly, and becomes low-temperature and low-pressure wet steam, and then enters the evaporator.
4. The role of the evaporator: The low-temperature condensed "liquid" body passes through the evaporator to exchange heat with the outside air, and "gas" absorbs heat to achieve the effect of cooling. The evaporator is mainly composed of a heating chamber and an evaporation chamber. The heating chamber provides the liquid with the heat required for evaporation, which promotes the boiling and vaporization of the liquid; the evaporation chamber completely separates the gas and liquid phases. The vapor generated in the heating chamber carries a large amount of liquid foam. After reaching the evaporation chamber in a large space, these liquids can be separated from the vapor by the action of self-condensation or defoamer. The demister is usually located on top of the evaporation chamber.
The evaporator is divided into three types: normal pressure, pressurization and decompression according to the operating pressure. According to the movement of the solution in the evaporator, there are: ① circulating type. The boiling solution passes through the heating surface many times in the heating chamber, such as the central circulation tube type, suspension basket type, external heating type, Levin type and forced circulation type. ② One-way type. The boiling solution passes through the heating surface once in the heating chamber without circulating flow, and the concentrated liquid is discharged, such as rising film type, falling film type, stirring film type and centrifugal film type. ③Direct contact type. The heating medium is in direct contact with the solution for heat transfer, such as an immersion combustion evaporator. During the operation of the evaporation device, a large amount of heating steam is consumed. In order to save heating steam, a multi-effect evaporation device and a steam recompression evaporator can be used.
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