Numerical analysis of nanomaterial-based sustainable latent heat thermal energy storage system by improving thermal characteristics of phase change material.

Abstract

Thermal energy conversion and storage plays a vital role in numerous sectors like industrial processing, residential and mass cooking processes, thermal management in buildings, chemical heating, and drying applications. It will also useful in waste heat recovery operations in industrial/thermal power stations. The effect of Al2O3 nanoparticle volume fraction (0%, 2%, and 5%) in a paraffin phase change material (PCM) and heater location (Bottom and Sidewall) in a 2D square thermal energy storage system have been numerically analyzed in this study. Transient thermal analysis has been carried out in ANSYS Fluent R18.1 for 500, 1000, and 3000 s. Laminar flow conditions with an enthalpy porosity model are used to study the solidification and melting behavior of nano-PCM. A Grid independence test has been conducted and selected an optimum number of elements as 115538. The results revealed that the addition of nanoparticles in PCM improves its thermal characteristics. The variation of liquid fraction and temperature profile with time has been recorded, and this is due to Rayleigh-Benard convection. At a given time, the melting rate increases with an increase in nanoparticle concentration up to 2% insertion after that the melting fraction reduces for both bottom wall and sidewall heating. This is mainly due to viscous domination with the increase in physical characteristics like density and viscosity of the fluid. Also, the melting rate in the case of sidewall heating augmented more than the bottom wall heating due to negligible buoyancy effects in former than later. The outcome of this analysis helps to find out the optimum volume concentration of nanoparticles to maximize the thermal energy storage applications.