Transient Numerical Analysis of Coupled Convection– Radiation–Latent Heat Transfer in a Partially Open Cavity with Variable-Heat Blocks and Hybrid Fins

This numerical study aims to optimize the cooling of three variable-heat blocks arranged in a partially open rectangular cavity. A conductive plate, separating an air region from another containing a phase change material (PCM), supports the heat-generating blocks. Each block has one half-surface in contact with air, equipped with porous fins, and the other in contact with the PCM, fitted with solid fins. The coupling between convection–radiation in the air and conduction–latent heat storage in the PCM enables more efficient thermal management. The numerical modeling, based on the Galerkin finite element method, investigates the influence of several parameters, including the Reynolds number \(\:(200\le\:\text{R}\text{e}\le\:1000)\), emissivity \(\:(0.1\le\:{\upvarepsilon\:}\le\:0.9)\), fusion temperature (\(\:300\:\text{K}\le\:{\text{T}}_{\text{f}}\le\:315\:\text{K})\), latent heat \(\:(192.12\:\text{k}\text{J}{\:\text{k}\text{g}}^{-1}\le\:{\text{L}}_{\text{f}}\le\:272.12\:\text{k}\text{J}{\:\text{k}\text{g}}^{-1})\), block radius \(\:(0.1\:\text{c}\text{m}\le\:\text{r}\le\:0.35\:\text{c}\text{m})\), block displacement toward the PCM \(\:(0\le\:\text{d}\le\:0.15\:\text{c}\text{m})\) and inclination angle \(\:(0\text{ᵒ}\le\:\le\:180\text{ᵒ})\). The results show that increasing the emissivity \(\:({\upvarepsilon\:}=0.9)\) lowers the maximum temperature by about 6 K, while a higher Reynolds number further reduces it by up to 6%. A PCM with higher latent heat decreases the maximum temperature by 3.48%, confirming the effectiveness of latent heat storage. The optimal inclination angle \(\:\left(=135^\circ\:\right)\:\)enhances heat dissipation, whereas enlarging the block radius increases the maximum temperature by up to 19%. These findings highlight the crucial role of convection–radiation–latent heat coupling in the design of high-performance and thermally stable electronic cooling systems.