Numerical Studies of Flow and Temperature Distribution in a Micro‑heat Exchanger

摘要

In the design of micro-heat exchangers, the flow and temperature uniformities are essential parameters for achieving better performance. In this work, uniformity of flow and temperature distributions was numerically studied in parallel micro-channels. Carboxymethyl cellulose (CMC) aqueous solution (0.5 wt.%) was used as a cooling (working) fluid. The rheological behavior of this solution is as power-law non-Newtonian fluid. Different manifold structures were used, and the effect of them on the flow and temperature distributions was studied. Results found that rectangular structure has lower values for temperature difference and uniformity parameter than other cases. So, with the rectangular structure of manifold, temperature and flow distributions are more uniform. In the next consideration, the direction of the inlet flow to micro-channels was studied. Three directions (vertical (90°), horizontal (0°) and oblique (45°)) were used. With different directions, various velocity profiles in the micro-channels were shown. As, with horizontal inlet flow, velocity in middle micro-channel is higher than other micro-channels, while, with vertical inlet flow, the first micro-channel has maximum velocity and velocity decreases in next micro-channels. Also, between these three directions, horizontal inlet flow has better uniformity of flow and temperature.