Close-contact melting enhancement mechanisms in space-constrained and large-space containers

To address the critical challenge of low latent heat storage efficiency, this work explores the performance gains of efficient close-contact melting (CCM) compared to traditional constrained melting (CM) in different containers. A novel CCM model based on the quasi-steady-state method is developed and experimentally validated. The comprehensive performance of CM and CCM in space-constrained containers (SCCs) and large-space containers (LSCs) is compared, and the influence of aspect ratio and heat flux density on the performance differences between the two melting modes is investigated. The study indicates that the performance of CM depends on the competition between conduction attenuation and natural convection enhancement, whereas mixed convection in CCM weakens convective heat transfer, with performance primarily dictated by the heat conduction of the thin molten layer. Based on the ranking of the reduction in melting duration of CCM relative to CM, containers with different spatial structures are ordered as follows: LSC (33.8 %) > vertical SCC (17.3 %) >horizontal SCC (3 %). As the aspect ratio approaches 1, the increase in melting rate and thermal homogeneity of CCM relative to CM becomes more significant. For situations where the aspect ratio deviates from 1, the enhancement gain of CCM over CM is greater in vertical SCCs than in horizontal SCCs. Additionally, increased heat flux density weakens the performance enhancement advantage of CCM over CM, especially in horizontal SCCs.