Compressor capacity and performance. Productivity of the compressor

In practice ARI Standard 500-2000 determines the efficiency of the compressor as the ratio of the isentropic work of the measured input power. Thus, the efficiency of the compressor becomes:

where m is the refrigerant mass flow, kg/s; h2s-specific enthalpy of the refrigerant vapor at discharge pressure at constant entropy (s1 = s2S), kJ/kg; h1-specific enthalpy of the refrigerant vapor input compressor, kJ/kg; P is the measured input power of the engine, kW; n_c the efficiency of the compressor.

Note that the other compressor efficiency, volumetric efficiency, can be approximately represented in terms of the ratio of the clearance volume of displacement, (R), and concrete volumes of refrigerant in the compressor (suction), and exit (reset) (v1 and v2), as follows:

Also, please note that the cooling capacity can be defined in terms of the compressor volumetric speed of displacement of the V (m3/s), volumetric efficiency of the compressor ( v ) , the density of the refrigerant in the compressor (p1, kg/m3), and enthalpies of specific refrigerant entering the compressor and the expansion valve at the inlet. It is then written as

Further details on the practical implementation of the evaluations and ratings compressors, and also definitions of the compressor related elements are presented in a widely-ARI (2000) and Klein et al. (2000).

Although there are a number of issues that affect the efficiency of the compressor, the most significant of them is the temperature, Elevator (or compression). To a lesser extent suction temperature, lubrication and cooling system also play an important role. Therefore, such decisions to improve the efficiency of the compressor to be decisive.

Minimization of temperature rise. The compressor is most effective when low condensing pressure and evaporation pressure is high, leading to the minimum temperature Elevator, and compression level. Effects of operating conditions is illustrated by the data compressor in the example in Fig. 3.16. In this regard, good design of the system must ensure that condensing pressure the lowest boiling point temperature is as high as possible. Design of systems with a small condenser and the evaporator to reduce capital costs is always a false economy. The use of the evaporator and condenser, often means a smaller compressor can be used and always reduces operating costs. An additional advantage is that the compressor will be more reliable, because it doesn't need to work hard and operates with lower discharge temperature.
Lower intake temperature. The lower suction gas temperature, the greater the capacity with no effect on the power. Discharge temperature will also be lower, thus increasing reliability. Suction line isolation is necessary.

Effective and lubrication cooling. The compressor should be lubricated and effectively cooled. Insufficient lubrication of the bearing increases friction and temperature and reduces the efficiency of the compressor, which often leads to failure.