Comparison between variable displacement and variable speed compressors for electric vehicle heat pumps
Zhaohua Li, Tao Liu, Xinwen Chen, Hanyu Zhu, Changtong Xu, Kun Liang
Abstract
Recent developments in electric vehicles have heightened the need for high-efficiency heat pump technology to improve cruising range and cabinet thermal comfort. As the key component for a heat pump system, compressor has a significant impact on heat pump system performance. In this work, a numerical model of a heat pump system consisting of a variable displacement compressor (VDC) model, a variable speed compressor (VSC) model, and a heat exchanger model is presented to compare the two major types of compressor. The simulation is executed across a diverse array of conditions to assess the performance disparity between two variants of compressors, particularly in challenging environments. The proposed model is validated based on the experimental data from a heat pump test rig which compressor section can be replaced with a prototype VDC or VSC based on validation demands. Overall, the modeling results demonstrate a favorable alignment with the measurements. The simulated power input of VDC under heat and cooling mode has a mean absolute percentage error (MPAE) of 4.4% and 6.0%, respectively, while the MAPEs for VSC under heating and cooling modes are 3.2%, and 4.5%. The modelling results indicate that the VDC system shows superior performance in specific mass flow rate, compressor power input, and system efficiency, especially at part load conditions.