Transient study of phase change material based hybrid heat sink for electronics cooling application

This work proposes a hybrid heat sink in which primary cooling is achieved by PCM (Phase change material), whereas the second one is based on liquid channels. The purpose of the liquid channel is to extract the heat from PCM in order to re-solidify it intermittently as per the requirement. A three-dimensional plate-fin heat sink [20 mm (L) x 3 mm (W) x 10 mm (H)] with inter-fin spacing filled with PCM and a channel embedded inside the tip of the fin is employed in this study. Three-dimensional transient numerical simulations are performed to identify the optimum operating condition governed by energy consumption and the liquid fraction of PCM. Simulations are performed at different heat flux (5 - 15 W/cm2), and inlet velocity (0.5 – 1.5 m/s). Parameters such as PCM-heat source interface temperature, the liquid fraction of PCM, pressure drop are recorded for each case. It is observed that the time taken to reach critical operating temperature varies inversely with heat flux. The cooling rate is a direct function of inlet velocity; however, temperature decreases exponentially, especially at higher heat flux. The importance of fast recharging/re-solidification of PCM at a low energy consumption cost is envisioned. For the heat sink configuration studied here, an optimum heat flux of 10 W/cm2 is identified at which a substantial reduction in liquid fraction can be achieved in a short duration of time at inlet velocity ≥ 1 m/s. More emphasis is given to energy consumption rather than flow time used in secondary cooling. A lower liquid fraction at the end of secondary cooling (i.e., partial melting of PCM) ensures the safe operating condition for electronic devices even in the presence of the impulse of heat generation. The findings presented in this work is useful to design PCM based hybrid heat sink for electronics cooling.