Thermal optimization of hollow clay brick integrated with phase change materials

Abstract

Lightweight construction materials are increasingly adopted in high-rise and super- high-rise buildings due to their structural efficiency, ease of construction, and reduced

structural mass. However, the extensive use of such materials is often associated with low thermal inertia, which adversely affects the thermal performance of building envelopes. The reduced capacity to store and release heat leads to pronounced indoor temperature fluctuations, increased peak cooling and heating demands, and a consequent deterioration of indoor thermal comfort, especially in regions with extreme climatic conditions. In hot-dry climates, where buildings are subjected to high solar radiation and large diurnal temperature variations, the limitations of lightweight walls become even more critical. Under these conditions, conventional lightweight building envelopes exhibit limited ability to attenuate heat transfer and delay thermal peaks, resulting in elevated reliance on mechanical air-conditioning and heating systems. This increased dependency not only raises energy consumption but also contributes to higher operational costs and environmental impacts. To overcome these challenges, the integration of phase change materials (PCMs) into building components has emerged as a promising passive thermal regulation strategy. When incorporated into building bricks, PCMs significantly enhance the thermal energy storage capacity of lightweight walls, thereby improving the thermal inertia of the wall system. Within this context, the present research investigates the thermal optimization of lightweight hollow clay brick walls through the integration of PCMs under real climatic conditions representative of hot-dry regions. A novel brick configuration incorporating two different PCMs in a double-layer arrangement is proposed to enhance thermal energy storage and improve dynamic thermal performance. The study adopts a transient numerical methodology based on Computational Fluid Dynamics (CFD), incorporating phase-change heat transfer models developed and validated using ANSYS Fluent. The thermal behavior of the proposed double-PCM layer brick is systematically analyzed and compared with conventional air-filled bricks and single-PCM layer configurations. Key performance indicators, including indoor temperature evolution, heat flux, decrement factor, and time lag, are used to quantify thermal performance improvements. The results demonstrate that the double-PCM layer configuration significantly outperforms conventional and single-PCM solutions by reducing peak indoor temperatures, attenuating indoor heat flux, and enhancing time lag, thereby improving indoor thermal comfort and reducing cooling energy demand.

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Furthermore, a comprehensive parametric investigation is conducted to assess the influence of PCM layer thickness and positioning on thermal performance. The findings indicate that positioning the PCM with a higher melting temperature on the exterior side and the PCM with a lower melting temperature on the interior side, with equal layer thicknesses, yields the optimal thermal response. This configuration maximizes heat storage efficiency and effectively shifts thermal loads away from peak outdoor temperature periods. Overall, this thesis provides a detailed numerical framework and practical design guidelines for the integration of multi-layer PCM systems into lightweight building envelopes. The outcomes contribute to the development of energy-efficient and climate-responsive building materials, offering effective solutions for reducing cooling energy consumption and improving thermal comfort in buildings located in hot-dry climatic zones.