Field performance measurements of a VRF system with sub-cooler in educational offices for the cooling season

The effects of the subcooling heat exchanger (SCHX) on the performance of the multi-split variable refrigerant flow (VRF) system with long pipe were investigated in a field test during the cooling season. By varying the refrigerant mass flow rate via the electronic expansion valve, the degree of subcooling was controlled. It was found that VRF system with SCHX improved the cooling performance factor (CPF) about 8.5% under similar outdoor temperature profiles, as compared to the baseline without SCHX. However, when the fraction of total refrigerant that passes through the SCHX was higher than 5.27%, the CPF starts to decrease due to the decreased refrigerant mass flow rate through the evaporators. Employing a SCHX in a VRF system with long pipe was found to be an effective method for improving the system performance and reliability.

► The benefits of subcooling heat exchanger are investigated through VRF system field performance tests.
► Subcooling heat exchanger improves the performance of a VRF system.
► There is an optimum refrigerant mass flow rate to subcooling heat exchanger maximizing the performance.