A simple model to predict the thermal performance of a ventilated facade with phase change materials
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Appropriate design and control strategies are crucial for the implementation of certain complex active systems in the building sector. Suitable and user-friendly numerical tools have to be available to architects and engineers, so they can incorporate innovative active systems in their building designs. The thermal response of a ventilated facade with phase change material in its air chamber for cooling applications is studied in this paper. The system makes use of low temperatures at night to solidify the phase change material, and store it solid for a later cooling supply to the interior of the building. This active technology is very sensitive to the weather conditions as well as to the defined operational schedule (charge, storage and discharge periods definition). Two different numerical approaches have been developed to better understand this system and to define different control strategies, as well as to determine their potential to reduce the energy consumption in the building for cooling purposes. First, a finite control volume approach was applied to describe the ventilated facade with latent heat storage. The important computational cost and complexity of this numerical methodology leaded the authors to develop a simple numerical model based on the assumption that the exchange between the air and phase change material inside the ventilated facade occurs at isothermal conditions. Both models were validated against experimental data, and even though the isothermal model presented slightly higher deviation from the experimental results than the finite control volume one, it is presented as a suitable numerical tool for architects and engineers because of its light computational cost and versatility.