Analysis of non-uniform flow distribution in parallel micro-channels

Micro heat exchangers have been widely used in both of academic and industrial fields for controlling heat for decades. Especially, the printed circuit heat exchanger (PCHE) is applicable to high pressure and high temperature cases since the manufacturing process, diffusion bonding, gives high durability. However, flow does not occur uniformly in multiple channels, which causes a heat transfer difference between the channels that reduces the effectiveness of the system. Also, it makes the total pressure drop larger than when it is uniformly distributed. Flow distribution has been studied intensively for decades, but the mechanism has not been clarified yet, since flow in the header is much too complicated. As a step to reveal the mechanism, we focus on maldistribution and quantitatively investigate the phenomena. We prepared experimental devices, including a set of parallel micro-channels, inlet and outlet. We used water as a working fluid, and water soluble red ink for visualization. We measured the interface location to derive the flow speed at each channel. We focused on the dependency of channel length and flow speed. In the theoretical part, we derived the flow speed profile of the entire channels that shows good agreement with the experimental results. This study provides a theoretical basis on resolving the maldistribution problem.