Effects of fin slope on the overall thermal conductance of heat sinks in forced convection

Results of previous studies indicate that increasing the fin slope, while keeping the fin surface area fixed, can enhance the overall thermal conductance of the fin. Here, to understand such enhancement, an isothermal fin theory is used to calculate the dependence of the fin cooling capability on the fin slope. The theory suggests that because a sloped fin has more surface area allocated to the region where the local heat transfer coefficient is larger, the overall thermal conductance of the fin thus is increased. Also, by using the commercial software FloWorks, numerical simulations are carried out to validate the theory. In addition, FloWorks simulations for heat sinks consisting of a series of identical sloped fins also show that their cooling capability increases with the fin slope. Examination of the corresponding flow and temperature fields suggests that the improvement is related to a reduction in the effective path length that the cooling air current takes to pass the heat sink. Based on the above findings, a bi-triangular fin geometry design that further increases the thermal conductance of the heat sink is proposed.