Modelling the Flow and Heat Transfer Characteristics of Perforated Foldcore Sandwich Composites for Application in Room Air Conditioning

In this work, the use of foldcore sandwich elements for building ventilation is investigated. Lightweight folded structures as an alternative to conventional sandwich core materials with the potential to be used for air or fluid transport have been investigated in aerospace engineering. Their high specific stiffness and strength in combination with multifunctional properties permits a reduction of system mass without sacrificing structural performance. Applied to the context of civil engineering, the embodied energy inherent to complex ventilation system may be reduced by the use of multifunctional, lightweight components. This work proposes an application in ultra-lightweight buildings as wall, ceiling or façde elements with integrated air ducts and large two-dimensional ventilation outlets by perforating the room-facing surface layer of the sandwich. The resulting element combines convective and radiative heating in a novel way by thermally coupling the airflow of the space heater with the room-facing surface. The mentioned properties are investigated in theory by forming a 1-dimensional distributed parameter fluid-dynamical model resulting in a boundary value problem. This is extended by a formulation of the heat transfer between fluid and surface layer. The models are evaluated and their parameters identified in practice by analyzing a prototype on a test bench. The results are integrated into a building energy performance simulation in Modelica to enable simulative studies of the impact on building occupant comfort.