制冷基础-CPI.pptVIP

* The four main components for every refrigeration circuit are the compressor, condenser, expansion valve and evaporator. The compressor compresses the gas. The result is a transfer of the mechanical energy or work of the compressor into internal kinetic energy within the refrigerant. The temperature of the gas increases with the amount of work done. The condenser removes the heat of compression from the refrigerant. The result of this removal of heat is the liquefaction of the refrigerant. The expansion valve, or refrigerant control valve, meters the proper amount of refrigerant to the evaporator, reducing the pressure of the liquid so that it will vaporize in the evaporator at the desired low temperature. The function of the evaporator is to provide an efficient heat transfer surface through which heat can pass from the refrigerated space or product into the vaporizing refrigerant. * The compressor and discharge line deliver high pressure, high temperature gas to the condenser. The proper lubrication of the compressor is also the primary role of the lubricant for this portion of the system. In addition to lubricating the bearings of the compressor, the lubricant assists the compressor in sealing between gaps within the compressor and aids in the removal of heat from the compression process. Typically a separator is employed after the compressor to separate the lubricant from the discharging gas. The separator will effectively remove all (greater than 99%) of the lubricant from the gas stream. The primary property that is evaluated for lubricants in this portion of the system is solubility. You need to ensure that you have enough viscosity to lubricate the bearings, seal the voids and lubricate the seals. * The condenser functions as a heat exchanger for the system. It often uses air or water as the medium to reject heat. It is in the condenser that the importance of lubricant behavior with the refrigerant first becomes evident. If a lubricant i