Geometry Optimization and Thermal Design of Natural Convection for Heat Sinks with Straight Fins

Abstract

In this paper, geometry optimization and thermal design of natural convection for heat sinks with vertical straight fins are numerically investigated. To enhance heat transfer and improve temperature uniformity for natural convection heat sinks, steady state solutions of cases in which heat sinks arranged vertically are obtained using a commercially CFD software FloEFD. Flow and temperature distributions of cases with and without air deflectors installed between heat sinks are compared. The results show that, the air deflectors installed obliquely between heat sinks can interrupt hot air upwards flow and reduce the temperature difference between heat sinks. For a better heat transfer performance without increase fin weight, different outline shapes of straight fins for heat sinks, including rectangular, trapezoid and hyperbolic outlined are analyzed. As the fin outline changes from rectangular to trapezoid, higher heat transfer coefficient is obtained due to the fin distribution and entrance effect. An optimum ratio of the top height to bottom height for trapezoid fins with better heat transfer performance is determined. At last, hyperbolic fins are designed to enlarge the enhancement of heat transfer. Comparing to the original structure, the wall temperature of the bottom area of heat sinks decreases more than 3 ℃ with the same fin weight.