Accurate and streamlined approach for modelling hermetic reciprocating compressors

This study presents a comprehensive and streamlined approach for accurately modelling the performance of hermetic reciprocating compressors, with a focus on addressing limitations in existing models under variable-speed conditions. Traditional compressor models sometimes fail to capture the influence of motor frequency, particularly at low-speed operations where performance variations are significant. To overcome these gaps, a numerical modelling framework was developed using 1-D and 2-D polynomial regressions to represent volumetric and isentropic efficiencies as functions of both compression ratio and motor speed frequency. The modelling process utilizes input data from manufacturer tools and thermodynamic databases to cover a wide range of operating conditions. A case study involving the Bitzer 4HTE-20K CO₂ compressor demonstrates that the proposed speed-driven compressor model improves accuracy, particularly in the low-frequency range below 40 Hz. The proposed numerical model with predictions of compressor power input and discharge temperature has been validated against published experimental data within a ± 10% error margin. This refined approach enhances simulation precision by up to 19.4% at low-speed motor frequencies, offering a practical and reliable tool for academics, industry professionals, and system designers to accurately predict the performance of hermetic reciprocating compressors used in refrigeration and heat pump applications across diverse operational scenarios.