Ten basic performance parameters of refrigeration compressors (technical sharing)

Ten basic performance parameters of refrigeration compressors (technical sharing) 1. Actual gas transmission volume (referred to as gas transmission volume)    Under a certain working condition, the mass of gas delivered from the suction end to the exhaust end per unit time is called the compressor mass gas delivery amount under this working condition, and the unit is If calculated according to the volume of the inspiratory state, the volume of air volume is calculated in units. then    2. Volumetric efficiency    The volumetric efficiency of the compressor is the ratio of the actual air volume to the theoretical air volume   It is used to measure the effective utilization of the working volume of the cylinder of the displacement compressor.    3. Cooling capacity   Refrigeration compressor is used as an important part of the refrigerator and cooperates with other components in the system, such as heat exchangers, throttle devices, etc. to obtain the effect of refrigeration. Therefore, it is necessary to intuitively express its working capacity in terms of the amount of cold produced in a unit of time-the amount of cooling, the unit of which is one of the important performance indicators of refrigeration compressors. In order to facilitate comparison and selection, it is necessary to stipulate a unified working condition to express the cooling capacity of the compressor according to its unused usage conditions. Table 4-1 lists the different forms of single-stage small-scale reciprocating refrigeration prescribed by the relevant national standards of China The nominal operating conditions of the compressor and its operating temperature. According to the standard, the heat absorbed by the superheating of the suction working medium should also be included in the cooling capacity of the compressor.    Fourth, heat removal    Heat removal is the sum of the compressor's cooling capacity and the equivalent heat of the input power of some compressors, which is discharged through the condenser in the system. This parameter is a very important performance index for the compressor in the heat pump system; it must also be known when designing the condenser of the refrigeration system.    Actual refrigeration cycle    The actual refrigeration cycle or heat pump cycle shows that the compressor can discharge heat under certain working conditions.   The energy balance of the compressor is not difficult to find.   In the previous two forms   -The working fluid specific enthalpy at the compressor inlet.   -Compressor input power.   -The heat dissipation of the compressor to the environment.    Table 2-2 lists the nominal operating conditions of compressors used in heat pumps specified by the American Refrigeration Association ARI520-85 standard.    V. Indicated power and indicated efficiency    The indicated work consumed in the actual cycle per unit time is the indicated power Pi of the compressor, the unit is kw, which is equal to    where Wi is the actual cycle indicated work of each cylinder or working volume, the unit is J.    The indicated efficiency hi of the refrigeration compressor refers to the ratio of the theoretical work of the isentropic cycle required to compress 1 kg of working medium to the actual indicated work of the cycle. It is used to evaluate the completeness of the completion of the thermal process inside the compressor cylinder or working volume.    VI. Shaft power, shaft efficiency and mechanical efficiency The power transmitted by the prime mover to the main shaft of the compressor is called the shaft power Pe, and the unit is kW. A part of it, that is, the indicated power Pi, is directly used to complete the working cycle of the compressor. , Used to overcome the friction resistance of various moving parts in the compressor and drive the attached equipment, such as hydraulic pumps for lubrication.    Seven, electric power and electric efficiency    The power input to the motor is the electric power Pel consumed by the compressor, in kW. Electric efficiency* is the ratio of isentropic compression theoretical power to electric power, which is used to evaluate the perfection degree of using the input power of the motor.    8. Performance coefficient    In order to finally measure the power economy of refrigeration compressors, the coefficient of performance COP (Cofficient of performance) is used, which is the ratio of the refrigeration capacity of the refrigeration compressor to the power consumed under certain working conditions.

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