Numerical Investigation on Flow and Heat Transfer in a Lattice (Matrix) Cooling Channel

Abstract

Flow and heat transfer of lattice cooling channel are investigated numerically. Firstly, simulations are performed for two channels to reproduce the experimental results reported in open literatures. Based on the literatures, sub-channels consisting lattice network are designed with aspect ratio of near unity and crossing angle of 45 degrees. Predicted heat transfer patterns of primary surfaces have agreed qualitatively and quantitatively well with the experimental results. Cooling air turns mainly through turning at the end of each sub-channel. After impinging the sidewall, strong acceleration occurs at the entrance of the opposite sub-channel, which enhances local heat transfer. Based on the above discussions, the present study also compares heat transfer coefficient of all surfaces (rib + primary) surrounding the sub-channel. The highest local heat transfer coefficient is found at rib surfaces. Predicted flow pattern indicates that a longitudinal vortex is formed in parallel to the sub-channel after impinging the sidewall, and that transient flow from one to another side of the sub-channels keeps the core of the vortex. This transient flow substantially contributes to the heat transfer enhancement at the upper edge of a rib surface, and more than half of total heat flux transfers through the rib. It follows that, in designing lattice cooling channel, rib surfaces should also be treated as heat transfer surface. Moreover, the effect of sub-channel (or rib) inclination angle on flow and heat transfer is examined. Rib inclination angle strongly affects translation flow between the lower and upper sub-channels and impingement at the sidewall. Further experimental investigation is expected in the near future.