Influence of Shrinkage on Phase Change Material-based Thermal Rectifiers

Abstract

Thermal rectifiers have recently emerged as a field of interest because of their potential application in a wide-ranging field. Thermal rectifiers can be employed to shield heat-sensitive electronics components, building thermal management and thermal energy conversion. A thermal rectifier allows heat transfer in a preferred direction while curtailing heat transfer in the reverse direction. Recently, the thermal conductivity differential of Phase Change Materials (PCMs) in their different states has been employed to develop thermal rectifiers. However, these studies are limited to analyzing the effect of change in the thermal conductivity alone, neglecting the influence of change in other thermophysical properties. The difference in PCM density in different states leads to the development of void volume upon phase transition, which can significantly alter thermal rectification. Therefore, this study analyzes the interdependent influence of thermal conductivity and density on thermal rectification under a wide range of temperature biases. The presence of void volume under reverse bias augments thermal rectification, whereas it has an adverse effect when developed under the forward bias. A criterion is developed to identify when the influence of density negates that of thermal conductivity, which requires the design of the thermal rectifier to be altered. Furthermore, optimization criteria and expressions for optimal thermal rectification are developed, incorporating the influence of both thermal conductivity and density.