A novel approach for suppressing flow maldistribution in mini-channel heat exchangers

Abstract

Mini-channel heat exchangers are extensively used to achieve heat dissipation with high heat flux, while the problem of flow maldistribution seriously impairs the thermal efficiency and operational reliability of heat exchangers. In this paper, the flow distribution characteristics of mini-channel heat exchangers with the conventional manifold model are numerically studied, and the influence of flow maldistribution on heat transfer is analyzed. To suppress the problem of flow maldistribution, an innovative approach for improving fluid uniformity by the built-in spiral baffle in the inlet manifold is proposed, and the effects of spiral baffles with different pitches and radii on flow distribution are discussed. Besides, the heat transfer characteristics and pressure drop under different manifold models are also compared. Finally, the variable-pitch spiral baffle is introduced to realize the stepped regulation of flow distribution. The results show that the conventional manifold model has serious flow maldistribution and causes the deterioration of heat transfer in front-end channels, especially at high Reynolds numbers. The improved manifold model greatly improves the uniformity of the fluid and temperature distribution inside mini-channel heat exchangers on the premise of sacrificing a small amount of pressure drop. The optimal pitch and radius of the spiral baffle are 20 mm and 9 mm respectively, and the flow maldistribution in almost all channels is controlled within the range of ±15% at this case. In addition, the variable-pitch spiral baffle further improves the flow uniformity of the mini-channel heat exchanger, and shows better overall performance than the equal-pitch spiral baffle.