Thermal response to periodic heating of a heat sink incorporating a phase change material

Abstract

Phase change materials (PCMs) can effectively dampen temperature fluctuations due to their high latent heat capacity, leading to decreased average cooling requirements in various engineering applications. However, there are few design guidelines for PCM-based heat sinks and there is limited experimental research on their performance in high heat flux, periodic heating conditions. In this work, we present a 0-D and 1-D nondimensional analytic model for PCM-based heat sinks subject to sinusoidal heating. We formally define the four possible responses of PCM-based heat sinks and derive expressions to predict their effectiveness. We test experimentally two PCM-based heat sinks to validate these expressions – an air-cooled system and a water-cooled system. The operating PCM is Field's metal (32.5-Bi, 51-In, 16.5-Sn), a eutectic alloy with a melting temperature of 60 °C. Thermocouples are embedded in the system to measure the evolution of the system's temperature over time. We apply a sinusoidal heat input and study the parametric response of these heat sinks under a wide range of heat flux amplitudes (1-100 W/cm2) and periods (5–640 s), while also varying the external heat transfer coefficient (1,700-18,700 W/m2K), ambient temperature (20–45 °C), and thickness of PCM (1–4.4 mm) to comprehensively validate these proposed models. The experimental results are plotted in phase space and show good agreement with the analytic predictions.