Numerical study on performance comparison for sub-cooling methods using a sub-cooler in a multi-split variable refrigerant flow (VRF) system.

Abstract

In this study, the performance of the VRF systems applying a bypass cycle and injection cycle using a sub-cooler is compared by numerical method. In the simulation for a multi-split variable refrigerant flow (VRF) system, it is important to predict the input power and mass flow rate of a scroll compressor with considering the refrigerant injection process in a compression chamber, and pressure drop and heat transfer in pipe lines between an outdoor unit and indoor units. Therefore, the simulation for a multi-split VRF system was developed with considering those, and validated with experimental data. The bypass and refrigerant injection have improvement potential to increase the cooling capacity due to increasing enthalpy difference in an evaporator. The refrigerant injection cycle has more improvement potential of performance than bypass cycle. Sub-cooling degree at inlet of EEV is above 10°C degree in two cycles, which can avoid flash gas generation.