Effects of tip gap and amplitude of piezoelectric fans on the performance of heat sinks in microelectronic cooling

Piezoelectric fan is a promising option for cooling microelectronic devices owing to its unique features such as no electromagnetic noise, low power consumption and minimum space requirement. The recent interest is to integrate the piezoelectric fans (piezofans) with heat sink; this idea is widely accepted and researches are still underway. This article presents experimental analysis on the effects of tip gap (delta) and amplitude of piezofan vibration (alpha) on the heat transfer characteristics of finned heat sinks. Two heat sink configurations, namely A and B (with two and four fins respectively) each of which is arranged with three piezofans, are considered for the study. The transient temperature distributions for cases with and without piezofans are obtained for both the configurations, and compared. The heat transfer coefficient, thermal impedance, Nusselt number and Reynolds number are investigated as functions of delta and alpha. The effect of alpha on the fan effectiveness is also analyzed. It is observed that the configuration B has better cooling performance compared to A. Among the tested ranges of delta and alpha, the case with least tip gap (delta = 0.03) and highest amplitude (alpha = 5.29) is found to be the best; at this setting, the fan effectiveness is increased to almost 4 times compared to the case without piezofans.