04. Boiling and Multi-Phase Flow

Plate heat exchangers (PHE) have been widely used in refrigeration and air conditioning system, chemical reaction processes and many other industrial applications. While applying the plate heat exchanger as an evaporator in an air-condition system, refrigerant flows into the heat exchanger at two-phase condition with vapor quality of around 0.2. Most of liquid flow up to the channels near the inlet port but less liquid flow into the channels far away from the inlet port. While the refrigerant evaporated in the heat exchanger, partial dryout occurred in the upper part of the channels far away the inlet port and degrade the heat exchanger performance. This study provides experimental observations of two-phase refrigerant R-410A evaporating in two multi-channel plate heat exchangers. One of them with horizontal baffle plates in the inlet header and the other without. It is aimed to block part of the liquid flow up to the channels near the inlet region and reduce the liquid flow mal-distribution in each channel. The test results show that the heat transfer coefficients in the plate heat exchanger with inlet distributers are from 16% to 30% higher than that without inlet distributers at low Reynolds number flow conditions but no significant difference while Reynolds number is low. The inlet baffle plates increased the overall flow resistance and caused a 3% to 22% pressure drops in comparing to the plate heat exchanger without inlet baffle plates.