Dynamics of PCM melting driven by spatially varying heat load

Melting of phase change materials (PCMs) finds applications in engineering systems such as heat sinks and latent heat energy storage (LHTES) modules. In real-time devices and systems, the heat load distribution is generally spatially varying, and hence, accurate measurements and modeling of PCM melting subjected to spatially varying heat flux inputs are very important. In this context, velocity field measurements and numerical simulations of PCM melting subjected to non-uniform heat flux distribution are presented herein. A transparent experimental setup for PCM melting with spatially varying heat flux loads has been constructed. The non-invasive particle image velocimetry (PIV) technique is employed to visually capture the liquid region's flow and velocity field distribution. A finite-volume method (FVM) based numerical model is employed to simulate the conjugate heat transfer and melting of PCM under spatially varying heat flux loads. Five cases with different configurations of heat flux distribution are considered. The numerical predictions are in good agreement with the experimental measurements. The variations in melt morphology and flow features caused by the spatially varying heat flux are highlighted. The heat transfer characteristics in each case are quantified in terms of Nusselt number and melting rates. Increasing the heat flux in the gravity direction aids natural convection and promotes faster melting rates at the bottom end of the cavity. On the other hand, decreasing the heat flux in the gravity direction hindered the natural convective flow and melting in the bottom end of the cavity. 40% decrease in total melting time is achieved by increasing the heat flux in the gravity direction. Decreasing the heat flux in the gravity direction led to a 44% increase in total melting time. The results of this study provide deeper insights into the dynamics of the PCM melting process subjected to spatially varying heat loads.