CFD-based numerical optimization of the thermal performance of PCM-integrated hollow bricks: combined effects of cavity geometry and phase-change temperature under hot-climate conditions

Abstract

This study presents a two-dimensional transient computational fluid dynamics (CFD) investigation of the thermal performance of hollow bricks incorporating air, glass wool, and phase change materials (PCMs) under the hot-climate conditions of Kairouan, Tunisia. Five brick geometries and three PCMs-RT26, RT30, and RT34 were evaluated over a 24 h thermal cycle using ANSYS Fluent R19. The numerical model, based on the enthalpy-porosity method, was validated against experimental data from the literature, with a maximum deviation below 3%. The solid brick exhibited the highest thermal load, with an energy demand of 191.78 Wh·m−2, whereas the air- and glass-wool-filled bricks reduced this value to 84.90 and 73.80 Wh·m−2, respectively. Among the investigated PCMs, RT30 achieved the best balance between latent-heat activation and thermal regulation, with an energy demand of 77.90 Wh·m−2 and a maximum liquid fraction of 0.45. RT26 melted completely but activated too early, while RT34 reached a maximum liquid fraction of only 0.28 and increased energy demand to 96.50 Wh·m−2. Increasing the cavity number from 8 to 12 reduced the transmitted heat flux by up to 57.65% under the investigated configurations. Overall, glass wool provided the lowest energy demand, while PCM performance depended strongly on the compatibility between its melting range, cavity geometry, and imposed thermal cycle.