Empirical modelling of a semihermetic reciprocating compressor for different CO2-based mixtures

Abstract

Mixing CO2 with other refrigerants gives carbon dioxide new thermophysical properties, such as higher critical temperature or lower working pressures.However, most of these new mixtures havenotyetbeenevaluatedexperimentally, introducing a lack of knowledge about how the main components of a refrigerating plant will operate with these blends.One clear example is the compressor, whose operationdirectly affects the performance and energy consumption of theplant. Accordingly, this work evaluates experimentally the behaviour of a CO2 semi-hermetic reciprocating compressor working with four different CO2-based mixtures of CO2/R32, CO2/R290, CO2/R1270 and CO2/R1234yf. The analysis covers the parameters of volumetric and global efficiency, discharge temperature, mass flow rate, and electrical power consumption, where noticeable differences are shown in terms of efficiencies, affecting the mass flow rate and the electrical power consumption significantly, and, to a lesser extent, the discharge temperature. The experimental results are compared with the standardized models from UNE-12900 and AHRI-540, proposing a simplified empirical model with a prediction error below 4% for all analysed mixtures and an extensive model for other CO2-based mixtures.