Effect of convection heat transfer on thermal energy storage unit

Abstract

Latent heat storage represents a promising technique to achieve net zero energy buildings. This work investigates the behaviour of phase change material (PCM) inside a rectangular enclosure, which represents the geometry of a latent heat storage system. The left side of the unit is exposed to a constant temperature (Th), while the other three walls are exposed to convection heat transfer boundary condition [h= 5, 10, and 15 W/(m2 K)] and different ambient temperatures (T∞ = 297° and 307°K). The ambient temperatures were selected to be at/above the melting temperature of the studied PCM (coconut oil). To study the melting process of the PCM, the continuity, Navier-Stokes and energy equation were used. The Navier-Stokes equations were modified using the Carman-Kozeny relation. The finite element method was utilized to produce numerical results. The results are presented in terms of flow and thermal fields, Nusselt number (Nu), and the melt fraction (MF) of the PCM. The results show that,when T∞ = Tm, the melting rate of the PCM slows down with increasing the convection heat transfer coefficient. While the melting rate accelerates with increasing the convection heat transfer coefficient when T∞ < Tm.