Modeling and Experimental Verification of the Electrical Efficiency for Variable-Frequency Rolling Piston Compressor under Variable Suction Conditions

Abstract

The frequency and the suction refrigerant state are complex in the actual operation of variable compressors, which leads to the variability of compressor performance under different operating conditions. The characterization and the modeling of the compressor have become hot research topics. For modeling, the electrical efficiency model of the compressor, which could be applied to the suction refrigerant state at both the superheated and the two-phase stages, the compressor frequency, the pressure ratio, and the evaporation temperature, is analyzed through experiments in this paper. The results show that the linear electrical efficiency decreases with the declining superheated temperature and the increasing suction vapor quality when the system is at the fixed and evaporating temperature. Moreover, the slope of the two-phase suction is above that of the superheated suction. In addition, the system’s electrical efficiency at the fixed pressure ratio is inversely proportional to the evaporation temperature, and the electrical efficiency of the system at the fixed evaporating temperature is also inversely proportional to the pressure ratio. The higher the variation of the pressure ratio, the smaller the evaporation temperature influences. To demonstrate the precision of the model, the theoretical value is compared with a confirmatory experiment in this paper. The maximum relative error is 1.81%, and the minimum is 0.035%.

Keywords

• variable-frequency compressor
• electrical efficiency
• modeling
• two-phase