Numerical investigation of latent heat thermal energy storage unit with different configurations and phase change materials

Abstract

In this work melting behavior of PCMs inside the LHTES (latent heat thermal energy storage) unit for six different cases has been numerically investigated by Comsol Multiphysics and Simulation Software. Two different PCMs (phase change materials), namely lauric acid and n-octadecane, have been used in the analysis for two different configurations. When configuration-1 has only one region for PCM, configuration-2 contains two regions. Simulations show that melting is completed at the upper side of the LHTES unit first due to the natural convection effects. On the other hand, it has been shown that LHTES unit in the form of configuration-1 with n-octadecane completes phase change earliest and absorbs most heat at the end of the process. This also demonstrates that not only latent heats of the PCMs, but also parameters affecting natural convection have an important effect on the heat transfer. Because when PCM with a lower melting temperature is used, buoyancy force, consequently absorbed heat increases. Inside boundaries also inversely affect absorbed heat by PCMs due to the non-slip boundary condition on these boundaries. The maximum efficiency of the LHTES unit is obtained for the configuration-1 with lauric acid due to not only high value of absorbed heat as a result of fewer obstacles of the geometry, but also the smaller values of latent heat and specific heat of lauric acid affecting Emax.