Experimental and visualization study on compact microchannel condenser with header-orifice liquid-vapor separator
Liquid-vapor separation enhances heat transfer and reduces pressure drop by optimizing refrigerant phase distribution. This technique has been implemented in parallel flow condensers in a simple and cost-effective manner by drilling orifices in the baffles. However, its performance under lower heat load conditions, relevant to compact heat pump system, has not been sufficiently studied, hindering its application in this industry. In this study, a series of microchannel parallel flow condensers with varied orifice positions were fabricated for thermohydraulic experiments. Several units were equipped with observation windows for flow visualization. Isobutane (R600a) was employed as the working fluid, with mass flow rates of 0.3 g/s and 0.5 g/s. The results demonstrate that the orificed baffle structure performs effectively when adequate liquid accumulates over it. The header-orifice condensers achieved an average pressure drop reduction of 0.43 kPa compared to the baseline, while maintaining nearly invariant subcooling degrees. Flow visualization confirmed the advantage of the tube-side orifice position in promoting liquid accumulation over other positions, thereby reducing gas entrainment into the subsequent condenser pass. This work provides practical guidance for applying headerorifice liquid-vapor separators in parallel flow microchannel condensers for low-heat-load applications.