Study of heat transfer and thermal rectification performances of a water-vapour chamber thermal diode and its application in a novel solar thermal power system

Abstract

A thermal diode is a device where the effective thermal conductivity in one direction is higher than that in the opposite direction. Among various types of thermal diodes reported in the literature, the phase-change thermal diode yields a greater thermal rectification performance. However, there are some limitations to the current phase-change thermal diodes, such as complex structures, complicated manufacturing procedures, and sophisticated working mechanisms. More importantly, some thermal diodes involve toxic, rare and expensive constituent materials. Hence, a simple water-vapour chamber thermal diode utilising the latent heat from pure water is designed, assembled and investigated, both experimentally and numerically in this study. The effects of the temperature gradient across the thermal diode, and the water-air volume ratio inside the water chamber on the heat transfer and thermal rectification performance of the water-vapour chamber thermal diode are examined. Mathematical models for anticipating the heat transfer performance of the proposed thermal diode are also built and verified by the experimental results. It should be noted that this is the first study to investigate this kind of thermal diode theoretically and experimentally. The findings reveal that the forward effective thermal conductivity of the thermal diode shows a 50 % enhancement when the hot side temperature rises from 40 ℃ to 70 ℃. A maximum diodicity of 1.43 is reported at the water-air volume ratio of 0.5. The results also indicate that the heat transfer and thermal rectification performances of the thermal diode is improved for a high water-air volume ratio. There are lots of applications for the thermal diode. In this study, a thermal diode based solar thermoelectric power system is established. The findings show that a maximum power output of 0.057 W is reported when the hot plate temperature is 120 ℃ and the cooling temperature is 10 ℃.

Date of Award	2019
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology