Abstract
In the last decade, the use of Phase Change Materials (PCMs) as passive thermal energy storage has been widely studied both analytically and experimentally. Among the PCMs, paraffins show many advantages, such as having a high latent heat, a low vapour pressure, being chemically inert, stable and non-toxic. But, their thermal conductivity is very low with a high volume change during the melting process. An efficient way to increase their poor thermal conductivity is to couple them with open cells metallic foams. This paper deals with a theoretical analysis of paraffin melting process inside an aluminum foam. A mathematical model is developed by using the volume-averaged governing equations for the porous domain, made up by the PCM embedded into the metal foam. Non-Darcian and buoyancy effects are considered in the momentum equation, while the energy equations are modelled with the Local Thermal Non-Equilibrium (LTNE) approach. The PCM liquefaction is treated with the apparent heat capacity method and the governing equations are solved with a finite-element scheme by COMSOL Multiphysics®. A new method to calculate the coupling coefficients needed for the thermal model has been developed and the results obtained have been validated comparing them to experimental data in literature.
Highlights
In the last years, the wide diffusion of technologies that can produce thermal energy from renewable and intermittent sources has increased the need for an efficient TES
The present study aims at developing a robust mathematical model based on the Volumes Of Fluid (VOF) method and the Volume Averaging Technique (VAT) using the non-thermal equilibrium approach, with physically based coefficients and a reasonable computational cost, in order to analyse and predict the phase change process characteristics with different metal foam properties
The results show that there is a threshold value of the volumetric heat transfer coefficient: for higher values, the temperature difference between the metal foam and the Phase Change Materials (PCMs) is negligible, so a LTE and a Local Thermal Non-Equilibrium (LTNE) model give basically the same results; for lower values the position of the melting front highly depends on the h@ value
Summary
- Experimental Study on Melting and Solidification of Phase Change Material Thermal Storage H Ambarita, I Abdullah, C A Siregar et al. - Review of Phase Change Materials Based on Energy Storage System with Applications R. - Phase Change Insulation for Energy Efficiency Based on Wax-Halloysite Composites Yafei Zhao, Suvhashis Thapa, Leland Weiss et al
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