The effect of the subcooling circuit on the cooling and heating performances of a multi-split VRF system was studied experimentally and a control strategy for multi-split VRF system with subcooling circuit is proposed in the paper. The results show that the subcooling circuit has a greater potential for improving the cooling capacity and the EER of the multi-split VRF system when the VRF system has a longer pipeline between the indoor units and the outdoor unit

a larger part-load ratio and a higher inlet water temperature of the outdoor unit

while the subcooling circuit has less influence on the heating capacity and the COP of the multi-split VRF system. Based on the results

a control strategy of the subcooling circuit is proposed

which takes the outlet subcooling degree of the outdoor unit

the compressor discharge temperature and the outlet superheat degree of the bypass stream in the subcooling heat exchanger as decision parameters and control targets of the subcooling circuit.