Experimental Study of Single-phase Change Material Thermal Diode Based on Calcium Chloride Hexahydrate

Abstract

Phase change material thermal diodes designed on the basis of different heat transfer forms and coefficients caused by different phase transition degrees in opposite heat transfer directions are considered as potential thermal management devices. However, the use of a variety of materials or only relying on numerical simulation research makes its structure complex or idealized, which reduces the possibility of practical application. Therefore, in this paper, a simple thermal diode structure containing only CaCl₂·6H₂O single-phase variable material was proposed in combination with changes in heat transfer form and heat transfer coefficient during solid-liquid phase change and natural convection process. The corresponding device was prepared, and a steady-state heat flux test system was set up for experimental study, the measurement accuracy was better than that recorded in literature. The influence of the temperature difference between hot and cold ends and the direction of positive and negative heat transfer on the thermal rectification effect of the thermal diode is studied experimentally. The results show that the heat flux of the thermal diode decreases with the decrease of the temperature difference between the cold and hot sources, and the thermal rectification ratio reaches up to 1.58 when the forward and reverse along the antigravity and gravity directions, respectively. The optimal cold source temperature range is 20-25℃, which is close to room temperature. The proposed phase change material thermal diode structure has certain application potential in building energy saving and thermal management.