Optimization of compressor load sharing in multiple fixed speed compressors heat pump.

In vapour compression system several technique are available to modulate both the refrigerant flow rate that flows through the compressor and the capacity that system delivers. Depending of the kind of compressor, strategies such as on-off cycles, piston unloading, sliding valve or rotational frequency variation are commonly used. Among them, despite its lower efficiency, on-off cycling is largely widespread due to its simplicity and ease to integration in system control. In the present paper, a numerical study is carried out in order to analyse the seasonal performance of a water-to-water heat pump, whose capacity control is achieved through compressor on-off cycling, considering both single and multiple parallel scroll compressors. Single compressor heat pump establish the baseline for performance optimization whereas different compressor load sharing in multiple compressor heat pump are analysed in order to find the optimum one for maximum seasonal energy performance.