Simplified steady-state modeling for variable speed compressor

This paper presents a detailed analysis of semi-empirical methods to calculate mass flow rate, shaft power and discharge temperature for three types of variable speed compressors: reciprocating, scroll and piston rotary. The proposed methods are an integration of physical-based models for constant speed compressor and the physical characteristics of volumetric efficiency and isentropic efficiency between different speeds. The physical-based models were first validated with good agreement with experimental data from publication for the three types of constant speed compressors. The comparison between modeling results and experimental data from publication for the three types of variable speed compressors shows the RMS errors are less than 3%, 3% and 3 °C for refrigerant mass flow rate, compressor power input and discharge temperature, respectively. The model of variable speed compressor will allow the reduction of the number of experimental data required to characterize variable speed compressor behavior in the modeling of refrigeration systems because of its physical mechanisms.

► Physical-based modeling of variable speed.
► Three types of compressors: reciprocating, scroll and piston rotary are investigated.
► Characteristics of volumetric and isentropic efficiency for variable speed compressor are explored.