Development of a phase change material (PCM)-based thermal switch

Abstract

© 2017 The Hong Kong Institution of Engineers. A thermal switch is an ON/OFF heat transfer control device which can be utilised in different modern fields such as cryogenics, solar energy systems, micro/nano-electronic cooling, the aerospace industry and building energy efficiency. In this study, paraffin wax is used to design and build a thermal switch based on phase change material (PCM). When the paraffin wax is heated and melts, one contact plate is pushed to make contact with another plate to turn the switch ON due to the pushing force generated by the volume expansion of the paraffin wax. Conversely, when the paraffin wax does not get enough heat to melt, the condition of the thermal switch is in the OFF state due to an air gap between the two plates. The ON/OFF thermal conductance ratio of the thermal switch is the major figure of merit and is investigated experimentally. The results show that the effective thermal conductivity of the PCM-based thermal switch in the ON state is recorded at 188.7 W/mK, while 6.2 W/mK is obtained in the OFF state. Therefore, the ON/OFF thermal conductance ratio is estimated at about 30.