Experimental investigation on distribution uniformity in multi-circuit evaporator with refrigerant gas separated and bypassed

Non-uniform distribution of gas-liquid refrigerant entering multi-circuit evaporators after throttling is a prevalent issue that significantly compromises efficiency. One effective solution to overcome this issue is to separate and bypass refrigerant gas to the outlet of the evaporators. Therefore, experiments were conducted to investigate the relationship between the effectiveness of gas-liquid separation, refrigerant distribution uniformity, and the performance of multi-circuit evaporators with gas bypass technology. Experimental results show that adjusting the bypass branch resistance is a key method for controlling gas separation efficiency under complete gas-liquid separation. Increasing the gas separation efficiency leads to significant improvements in the performance of multi-circuit evaporators, with maximum reductions of 70% in cooling capacity non-uniformity and 44% in evaporator pressure loss. Furthermore, the total superheat degree increases by 4.6 °C and 5.8 °C at total refrigerant flow rates of 60 kg/h and 80 kg/h, respectively, while decreasing by 0.4 °C at 40 kg/h. Without adjusting the bypass branch resistance, the difference in cooling capacity non-uniformity between gas bypass and conventional modes decreases with increasing quality at 60 kg/h and 80 kg/h. Particularly at 60 kg/h, the difference in total superheat degree between two modes initially increases before decreasing with rising quality, peaking around a quality of 0.18.