Experimental investigation of the effect of external forces on convection-driven melting of phase change material in a rectangular enclosure

Abstract

This paper studied the convection-driven melting characteristics of the pure phase change material (PCM) under different external force conditions. A centrifugal rotation experimental system was designed and built. The melting behavior of the PCM was investigated at the centrifugal accelerations of -5, -3, -1, 0, 1, 3 and 5 g with the heat flux direction as the reference direction. The melting photographs and recorded temperatures of PCM were used to calculate the melt fraction, time-averaged Nusselt number and latent heat storage. The results show that external forces have a significant effect on the natural convection of PCM during the melting process, which further affect the solid-liquid interface evolution rate, heat transfer rate and latent heat storage. To be specific, the external force in the opposite direction of the heat flux can promote the melting process of PCM. Compared with the case at 0 g, the full melting time is reduced by 30.56%, 44.44% and 51.39%, and the time-averaged Nusselt number is improved by 46%, 90% and 98% at -1 g, -3 g and -5 g, respectively. Under the reverse external forces, the melting rate and heat transfer coefficient of the PCM are significantly reduced. In addition, the external force has a significant effect on the latent heat storage of the PCM during melting. In short, it is better to use the external force in opposite direction of the heat flux to enhance the latent heat storage rate of the PCM.