Experimental studies of convective heat transfer enhancement for electronics cooling

Abstract

The enhancement of convective heat transfer, which is crucial on electronics cooling, is investigated by experimental endeavors. This thesis consists of common research on heat sink and advanced research on the effect of pulsating flow in channel for heat transfer enhancement. First, experiments have been performed to investigate the cooling performance of triangular folded fin heat sinks made of 6000 series aluminum in a duct flow. The fin height is varied from 19 mm to 36 mm and the fin pitch from 5.0 mm to 9.0 mm. The duct air velocity is in the range of 1.0 m/s to 5.0 m/s and the corresponding Reynolds number based on the hydraulic diameter is varied from 212 to 1974. The experimental results show that the cooling performance of triangular folded fin heat sink is influenced by the fin pitch, the Reynolds number and the fin height. It increases substantially as the fin pitch decreases and the Reynolds number and the fin height increase. By compiling the experimental data, the heat transfer and the friction factor correlations with ± 6.5 % and ± 20 % accuracy, respectively, are provided for effective design of triangular folded fin heat sinks. Second, experiments have been performed to investigate heat transfer enhancement from a heated square cylinder in a channel by pulsating flow. For all the experiments, the amplitude of the pulsating flow is fixed at A = 0.05. The effects of the Reynolds number based on the mean flow velocity (Re = 350 and 540), the pulsating frequency $(0 Hz < f_p < 60 Hz)$ and the blockage ratio of the square cylinder $(\beta = 1/10, 1/8, and 1/6)$ on convective heat transfer are examined. The measured Strouhal numbers of shedding vortices for non-pulsating (A = 0) steady inlet flow are compared with the previously published data, and good agreement is found. The "lock-on" phenomenon is clearly observed for a square cylinder in the present flow pulsation. When the pulsating frequency is within the lock-on regime, the heat transfer from...