(An) experimental and numerical study on the melting behavior of phase change material in vibration environments

Abstract

This paper reports an experimental and numerical investigation of the effects of random vibration on the melting behavior of phase change material (PCM) and the thermal performance of a PCM-based heat sink. While the random vibration of the overall acceleration from 2 to 16 g rms for the frequency range from 15 to 2000 Hz was applied to a rectangular container, in which paraffin wax as PCM and the heat sink were attached to each other, constant heat flux was imposed on the heat sink. Temperature recordings of the PCM and the heat sink, along with photographs of the melting front, during melting were analyzed to evaluate the melting heat transfer characteristics of the PCM and the performance of the PCM-based heat sink. The experimental results showed that the random vibration has no effects on the melting behavior early in the melting process during which conduction is the primary mode of heat transfer. However, the vibration significantly affected the melting behavior later in the process during which natural convection is the primary mode of heat transfer. The vibration augmented heat transfer in the molten PCM and increased the surface-averaged Nusselt number on the heat sink. The augmented heat transfer promoted melting of the PCM and delayed the rise in temperature of the heat sink. The time for the temperature of the PCM-based heat sink to rise to a threshold increased dramatically as the intensity of random vibration increased. A correlation for the surface-averaged Nusselt number was developed, devising the vibrational Rayleigh number to consider the effects of random vibration. A numerical method to simulate the thermal performance of the PCM-based heat sink under random vibration was devised and verified through the experimental results. Comparisons between the numerical and experimental results showed a good agreement for both static and vibration cases.