An experimental and numerical investigation on the use of phase change materials in building elements: The case of a flat roof in Istanbul

• A flat roof element incorporating latent heat thermal energy storage is evaluated.
• The results of an experimental study and CFD Software Analysis of PCM are compared.
• A flexible simulation model is generated.
• The use of different amounts of PCM in a roof for İstanbul, Turkey, is investigated.

This paper reports on the experimental and numerical analysis of a building element–a flat roof–that incorporates phase change material (PCM) as a layer. First, a planar model of the building element of 50 cm by 50 cm surface area was constructed in laboratory conditions to be used in the experimental work. During the experiment, changes in the thermal balance were investigated by temperature and volumetric flow rate measurements, as well as observation of the phase change interface. Next, the experimental measurements were used to validate a numerical computer fluid dynamics (CFD) model for simulation purposes. The model is one-dimensional and is based on the first law of thermodynamics. Finally, a time-dependent simulation for summer conditions was performed using the climatic data of İstanbul. The thickness of the PCM inside the roof element was investigated accordingly. The simulation data showed the solid/liquid phase of PCM over time. Monthly graphs were drawn for ease of comparison of the use of PCM with thicknesses varying between 1 and 5 cm. Consequently, a PCM thickness of 2 cm was found to be suitable for use in flat roofs in Istanbul.