A numerical study on the thermal buffering of bricks integrated with cylindrical phase change material capsules

While phase change materials (PCMs) in bricks are known to improve thermal mass, the influence of capsule geometry in hot climates remains poorly understood. This study evaluates the thermal performance of thermally smart bricks (TSBs) integrated with cylindrical heptadecane capsules reinforced with stainless-steel foam. Using a validated CFD model, we investigate a critical yet overlooked parameter: the capsule diameter (2, 3, and 4 cm) under varying peak outdoor temperatures (20–40 °C). Results show that PCM–foam capsules reduce peak indoor temperature by up to 1.9 °C, induce a 2–3-hour thermal lag, and lower heat flux amplitude by 35–40% compared to conventional bricks. At a peak temperature of 40 °C, the 4 cm capsules reduced daily power consumption by 31%, from 130 kWh/day to 90 kWh/day. We conclude that larger PCM–foam capsules offer superior thermal buffering, establishing TSBs as an effective passive solution for enhancing energy efficiency and thermal comfort in hot climates.