Optimal design and evaluation for sphere capsules in the packed bed latent thermal energy storage

Abstract

The high-performance PLTES basically relies on the heat transfer inside the sphere capsule. To achieve a high cost-performance enhancement, the sphere capsule with the copper foam partially filled is proposed, depending on the full utilization of the foam enhancement and natural convection. The melting performance of the partly filled sphere capsule and the optimization, including the geometric shape and foam material usage, is numerically investigated. The economic assessment of these initial cases and the optimized cases is also conducted to evaluate the economic feasibility. The numerical results indicate the partially filled strategy is effective and the optimal design is the spherical capsule with a copper foam geometric shape that resembles a high cone with a prominent center. This is because the buoyancy-driven natural convection is fully used to enhance the heat transfer in the upper section and the foam is used to enhance the heat transfer in the bottom section. Based on this analysis, a better effect can be obtained by maintaining consistent angle size while changing the height of the vertex of the high cone. Through this optimization, the usage of copper foam is reduced by 24.48 % at the same melting rate.