Analysis of ventilation effects and the thermal behaviour of multifunctional façade elements with 3D CFD models

This study determines thermal behaviour and airflow characteristics inside multifunctional façade elements. The façade elements investigated were designed in course of the research project “Multifunctional Plug & Play Facade” [1]. The integration of energy converting systems in a façade construction causes higher temperatures on the backside of the collectors impacting subjacent layers and the interior. Due to periphery openings, heat can partly be transferred to the exterior by the effects of natural ventilation. With the help of 'steady state' 3D Computational Fluid Dynamics (CFD) models of three different façade elements were investigated and compared. In particular this study presents a detailed analysis of airflow and the thermal behaviour of a photovoltaic module (PV), a solar thermal collector (ST) as well as a transparent single layer glass panel used as impact pane (TR) all integrated into the façade construction. Despite high temperatures in the solar thermal collector the lowest air temperatures inside the cavity were detected for the ST façade. The ventilation effects of the side openings were clearly identified in all façades. The numerical model includes the effects of heat transfer, buoyancy, radiation and the impact of solar radiation. Data from on-site measurement did largely match with the simulations' outcome.