Parametric Study of a Latent Thermal Storage Module
Abstract
Concentrated solar power generation has the potential to partially meet the future energy demand and reduce our dependence of fossil fuels. However due to the intermittent nature of this energy source, it has not been used for baseload power. This problem can be solved by implementing an efficient, economical and reliable latent heat (LH) energy storage strategy. An accurate heat transfer analysis will play an important role to make this strategy successful. This work presents a 2D numerical model of the diffusion-natural convective controlled heat transfer during an unconstrained (solid–liquid density difference) melting process of an encapsulated spherical thermal energy storage (TES) capsule filled with an inorganic salt as the phase change material (PCM). The melting of the PCM was modeled using the finite volume numerical procedure with a single-domain enthalpy formulation. Transient numerical simulations were performed using the CFD software Ansys-Fluent V 12.1. A detailed parametric analysis was carried out in order to analyze the geometrical and operational effects of the system and their influence on the charging times. The study focused on PCMs with melting point between 300°C to 400°C and metal coating materials subjected to a uniform wall temperature from 73°C to 93°C above the mean melting temperature of the PCM. The temperature profiles and interface positions for different Rayleigh, Stefan and Fourier numbers are determined. Computational results of this study show that for a fixed Stefan number (Ste=0.694) there is a significant difference in the flow fields for cases with Rayleigh number from 9.17x106 to 7.33x107.