Thermal behavior of a phase change material in a building roof with and without reflective coating in a warm humid zone

Abstract In this paper, the heat transfer in a concrete roof with an intermediate layer of PCM was studied numerically. Three positions and three thicknesses of the PCM layer and two values of solar absorptance (gray and white) of the roof were evaluated. The period studied was a typical summer week of a city in Mexico with warm humid weather. The interior boundary was in contact with the indoor air at a constant temperature. The unsteady two-dimensional model was solved by the Finite Volume Method using an implicit scheme. For the gray roof, the greatest reduction in the temperature of the interior surface (6.4⋄C) and in the heat gains (22.2%) was obtained when a PCM layer with a thickness of 2 cm is close to the interior surface. For the white roof, the results of the maximum temperatures of the interior surface and the heat gains between the different thicknesses and positions of the PCM layer showed negligible differences. However, the melting cycles of the PCM layer were affected as it was closer to the interior surface of the roof, and its thickness increased. The incorporation of a white reflective coating reduced the maximum interior surface temperature and the cooling load by 14.7–15.4⋄C, and 58.1–62.7%, respectively.