Effective Thermal Conductivity of Phase Change Material-Based Composites for High Heat Flux Electronic Cooling

Abstract

Abstract This work presents a simplified approach to optimally designing a heat sink with metallic thermal conductivity enhancers infiltrated with phase change material for electronic cooling. In present study, thermal conductivity enhancers are in the form of a honeycomb structure. A benchmarked two-dimensional computational fluid dynamics model was employed to investigate the thermal performance of the phase change material-metallic thermal conductivity enhancer composite heat sinks. Metallic thermal conductivity enhancers are often used in conjunction with phase change material to enhance the conductivity of the composite heat sink. Under constrained heat sink volume, the higher volume fraction of thermal conductivity enhancers improves the effective thermal conductivity of the composite, while it reduces the amount of latent heat storage simultaneously. The present work arrives at the optimal design of heat sink for electronic cooling by resolving the stated tradeoff. In this study, the total volume of the heat sink and the interfacial heat transfer area between the phase change material and thermal conductivity enhancers are constrained for all design points. Furthermore, assuming conduction-dominated heat transfer, an effective numerical model that solves the single energy equation with the effective properties of the phase change material- metallic thermal conductivity enhancer composite has been developed. The temperature gradient-time history is compared and matched for both the models to arrive at the accurate effective thermal conductivity value. The relationship of effective thermal conductivity as a function of metal volume fraction and thermal conductivity of metallic thermal conductivity enhancer is obtained. The figure of merit (FOM) is used to define the balance between effective thermal conductivity and energy storage capacity. The FOM is maximized to find the optimal volume fraction for the present design. The results from the study reveals that there exists an optimal metal volume fraction that maximizes the thermal performance of the composite.