Multicellular laminar natural convection in vertical bent cavities

This study concerns the heat transfer inside double glazing windows which bend because of extreme climatic conditions (an important temperature difference leads to a pressure drop inside the cavity which results in the bending of the plates). Four reference plane cavities of aspect ratio A = 40 with Rayleigh numbers varying within the laminar flow regime are considered. In each case, the influence on the convective heat transfer of the vertical surfaces bending inward is studied. A two-dimensional numerical simulation based on a finite volume method is performed to investigate natural convection in the air-filled cavities. Important curvature creates two patterns in the enclosure. In the core, heat is transferred more by conduction whereas in the ends multicellular convection occurs. A coefficient of heat transmission K is defined. K strongly increases with curvature. These results will be used to supply correlation allowing to take into account the curvature in the determination of the global coefficient of heat transmission U-factor established from ASHRAE.