microchannel evaporator, refrigerant distribution
This paper demonstrates that Flash Gas Bypass (FGB) method significantly improved the performances of the microchannel evaporator and the system, compared to the conventional direct expansion (DX) system. When system in both modes operated at the same compressor speed, the system in FGB mode produces about 13% to 18% more cooling capacity at 4% to 7% higher COP than in DX mode. When compressor speed was adjusted to maintain the same cooling capacity, COP improves 37% to 55%. Based on experimental results, a detailed microchannel heat exchanger model considering the refrigerant distribution helps to identify the two mechanisms augmenting the performances: 1) improved refrigerant quality distribution and 2) the reduction of refrigerant pressure drop across the evaporator.