Experimental investigation of the melting heat transfer of phase change material-based heat sinks under mechanical agitation with a no-delay-start strategy

Abstract

Phase change materials (PCMs) are commonly used for the thermal management of electronic devices, but their low thermal conductivity limits their suitability for higher heat fluxes and shorter heat storage/release durations. Existing studies on heat transfer enhancement have focused mainly on conduction and lack consideration of convection. Therefore, melting experiments on n-docosane under mechanical agitation (0–1600 RPM) were carried out. A no-delay-start strategy of agitation was achieved by submerging the paddle with the addition of water (200 and 400 mL). As the rotation speed (n) increases, the heating wall temperature (Tw) generally decreases, especially at 0–400 RPM. For 200 mL, Tw decreases by 31.2 °C from 0 to 1600 RPM at 3600 s; for 400 mL, the decrease is 29.2 °C at 5400 s. The temperature difference between the heating wall and PCM decreases remarkably under agitation, reaching only 2.7 and 1.7 °C for 200 and 400 mL, respectively, at 1600 RPM and 6300 s. The temperature field uniformity is also improved by agitation. In addition, with increasing n, the complete melting time (tc) generally decreases, while the holding time (thold) basically increases. Under agitation, the Tw values for 200 and 400 mL are generally lower than that for 0 mL, indicating that the no-delay-start strategy is feasible and advantageous. At n ≥ 800 RPM, Tw for 200 mL is greater than that for 400 mL throughout the entire melting process, while at n < 800 RPM, this trend occurs only during the solid-phase heat conduction stage. The effects of both the rotation speed and water volume depend on the combined function of the intensity of the PCM-water interface and the heat storage capacity of water. Even when the heat flux increases from 8.5 to 25.4 kW/m2, the thold can still be extended under agitation. The power consumption (Qc) of agitation increases with rotation speed, decreases with water volume, and exhibits less sensitivity to heat flux. It reaches a maximum value of 10 W at 1600 RPM. Considering factors such as Tw, thold and Qc, the optimal configuration is determined to be a water volume of 400 mL and a rotation speed of 1600 RPM. This study demonstrated that convection enhancement of PCMs with a no-delay-start strategy effectively addresses the thermal management challenges of electronic devices.