Heat transfer from micro-finned surfaces to flow of fluorinert coolant in reduced-size channels

Experiments were conducted in order to investigate the forced convective heat transfer from a micro-finned surface to a fluorocarbon liquid FX3250. The heat transfer surface is made from copper, has a base area 2 × 2 cm², and is equipped with 20 longitudinal fins, each fin being 0.5 mm high and 0.5 mm wide. Particular attention was directed to the effect of the channel height (H) on the heat transfer performance, changing H from 1 to 3 mm. The Reynolds number based on the hydraulic diameter covered a range from 1000 to 12000. Also conducted was an experiment using a flat heat transfer surface. It was found that the sensitivity of heat transfer performance to the change of H depends on the type of heat transfer surface. Comparisons are presented in terms of the heat transfer coefficient based on the actual heat transfer area. In order to interpret the experimental data the numerical simulation of flow and heat transfer was performed. The results render support to the heuristic assumption that the increased flow velocity in the free flow area above the fins in higher-height channels yield high heat transfer coefficients on the fin tips, offseting the degardation of heat transfer in the grooves.