An experimental study on the effect of vertical header geometry on the two-phase refrigerant distribution and performance of a microchannel heat exchanger

Micro-channel heat exchangers are widely used due to their superior performance compared to the existing fin and tube heat exchangers, but are limited to condensers due to refrigerant non-uniformity problems in evaporator operating conditions. Although many studies have been made to solve the refrigerant non-uniformity of the microchannel heat exchanger having a vertical header, a solution has not yet been proposed. In this study, a solution to the non-uniformity of the refrigerant was presented by applying a vertical header in the form of a double tube that can be applied to mass production. The effect of a double-tube form of the header on the refrigerant distribution and performance of a microchannel heat exchanger was explored by experimental means, using R-410A as the refrigerant. To investigate the effect of the shape of the header on the distribution of refrigerant in the final path of the heat exchanger and its performance, three types of multi-baffle and two types of multi-room header were considered. The tests were performed with an evaporation pressure in the micro channel heat exchanger of 800 kpa and a refrigerant flow rate of 50 to 80 kg/hr. The header with 5 independent refrigerant paths from the header inlet showed the most uniform distribution. The results showed a linear relationship between refrigerant distribution and heat exchanger performance. This study showed the effect of improving heat exchanger performance by up to 12% with the improved refrigerant distribution by applying a vertical header in the form of a double tube.