Micro-PIV visualization and numerical simulation of flow and heat transfer in three micro pin-fin heat sinks

摘要

This paper presents the experimental results of laminar flow behavior of water in circular micro pin-fin (C-MPF), square micro pin-fin (S-MPF) and diamond micro pin-fin (D-MPF) heat sinks using micro-PIV flow visualization technology at first. All three micro pin-fin heat sinks have a hydraulic diameter of 200 μm. Second, numerical simulation results of the fluid flow characteristics in these heat sinks with CFD are compared to the experimental results of fluid flow behaviors measured with the micro-PIV flow visualization. The normalized time averaged streamline patterns and instantaneous velocity contours in the three heat sinks were obtained for laminar flow of Reynolds number from 10 to 200. By comparison, the experimental results favorably agree with the simulated results of fluid flow. Of the three types of heat sinks, the vortexes occur the earliest in the D-MPF heat sink, which also present very complicated back flow. The strong vortexes and back flow effectively enhance the mixing of fluid and therefore lead to higher pressure drops in the D-MPF heat sink as compared to the other two types of heat sinks. The vortexes in the D-MPF heat sink are very much easily involved in the main flow than those in the other two types of heat sinks due to the high deceleration and pressurization zone. Finally, numerical simulation results of heat transfer at steady state in the three heat sinks are presented. The initial temperature of the working fluid and the ambient air is maintained at 293 K and a constant heat flux of qw = 400 kW/m2 is adopted in the central area at the bottom of the heat sink. The Reynolds number ranges from 40 to 300 for the fluid flow and heat transfer simulations. It shows that D-MPF heat sink has better heat transfer performance than the other two type heat sinks. The combined effects of the vortex in the main flow at the front side wall and the strong vortex intensity behind the D-MPF heat sink obtained in both experimental and numerical results may reasonably explain the better heat transfer enhancement behaviors as compared to those in the other two types of heat sinks. Further experiments on the heat transfer performance will be conducted to compare to the simulated results in the follow-up planned research.