Implementation of enhanced thermal conductivity approach to an LHTES system with in‐line spherical capsules

Abstract

In this study, the influences of inlet temperature and velocity of the heat transfer fluid and the capsule material on the performance of a latent heat thermal energy storage unit is numerically investigated. The enhanced thermal conductivity approach is implemented into the ANSYS‐FLUENT software to consider the natural‐convection‐dominated melting process within the capsules. The accuracy of the procedure is checked by comparing the current findings for inward melting against the numerical results from the literature. The comparative results reveal that the proposed approach is successfully incorporated, and the maximum deviation is obtained to be less than 10%. Results of the parametric analyses are represented regarding the first and second laws of the thermodynamics. The time‐wise variations of the melting front, the mean temperature of the phase change material, and the rate of entropy generation are evaluated. Increasing the inlet temperature and velocity of air significantly reduces the time for complete melting. The total time for melting is reduced by half when the inlet temperature of air is increased from Tm + 10 to Tm + 20 and the entropy generation rate increases more than four times. Besides, increasing the air inlet velocity from 0.5 m/s to 3.0 m/s doubles the entropy generation.

A simple method for the design of thermal energy storage systems

“…In line with this, Raul et al correlated heat transfer characteristics of a single PCM capsule and the storage system, resulting in a maximum efficiency of 75.69% for the minimum discharging inlet HTF temperature9 and Kurnia et al increased the heat transfer performance of a LHTES system by a multiple PCM arrangement 10. Metin et al analyse the influence of inlet temperature and velocity of the HTF and the capsule material on the performance of a latent heat TES unit 11…”

“…10 Metin et al analyse the influence of inlet temperature and velocity of the HTF and the capsule material on the performance of a latent heat TES unit. 11 On the other hand, research from the second group usually relies on optimization methods that minimize one or several performance parameters of the installation under analysis. In this way, Hübner et al determined, by parametric simulation, an optimum cross-sectional geometry for a finned-tube LHTES system integrated with a steam turbine.…”

A methodical approach for the design of thermal energy storage systems in buildings: An eight‐step methodology

“…A group of papers merely optimizes the thermal performance of TES systems. [25][26][27][28] However, the requirements for TES systems differ significantly depending on the chosen application. As a result, it is crucial to devise design methods that enable a TES system to meet the particular requirements of a given thermal application.…”

“…Identifying important factors and then matching an application with the most appropriate TES system is still a challenging issue. A group of papers merely optimizes the thermal performance of TES systems 25‐28 . However, the requirements for TES systems differ significantly depending on the chosen application.…”