Fluid flow and heat transfer in a latent thermal energy unit with different phase change material (PCM) cavity volume fractions

In present work, the effects of different cavity volume fractions of phase change material (PCM) on fluid flow and heat transfer behavior in a latent thermal unit are studied numerically. The commercial Computational Fluid Dynamics (CFD) package, Fluent, is used for the numerical solution based on transient conjugate heat transfer. The numerical results have been verified and validated against numerical and experimental data available in published literature. The volume expansion ratio, the time of complete thermal storage, heat flux, liquid fraction, velocity and temperature fields are investigated for the range of PCM cavity volume fractions (ϕmax) from 35% to 95%. It is noted that a vortex (as a heat transfer enhancer) is present near the heating plate wall for the PCM cavity volume equal to 85%. It is found that the volume expansion ratio decreases as ϕmax increasing, whereas the time for complete energy storage increases. Further, the correlations of the volume expansion ratio and the time of complete thermal storage are developed as a function of ϕmax. The detailed knowledge regarding interface heat transfer rate provides a deeper understanding the heat transfer mechanisms.

► The effect of PCM cavity volume fractions on latent thermal system is evaluated. ► A vortex appears and heat transfer is enhanced for cavity volume of 85%. ► The correlations of volume expansion ratios and completed storage time are developed. ► Heat transfer mechanisms are studied by analyzing the heat transfer rates.