Numerical And Experimental Investigation Of Natural Convection In Double Facades

Interests of this paper concern an active component of the building envelope: a photovoltaicthermal (PV-T) double-skin facade. This element consists of a vertical open air channel bounded by two parallel walls: one made of photovoltaic panels and one been the main frame of the building. The integration of this system in building facade remains not so obvious because electrical output is strongly dependent on the operating temperature of PV component. The aim carried out by our work is to promote a better cooling of the PV facade working on its typical geometrical arrangement. It consists of an alternation of PV cells (localized heat sources) and semi-transparent window panes (unheated zones). Fundamentally, the flow of natural convection which develops within the vertical channel appears to be subjected to boundary localized thermally active areas and adiabatic areas, periodically distributed on the height. That requires investigations on parametric variations of magnitude and space frequency of heated areas as well as intermediate spacing. The following approach, included in a joint research program between 3 laboratories, the CFD Research Laboratory UNSW (Sydney), CETHIL (Lyon) and DIPTEM (Genoa), in both the experimental and numerical nature of the work. Two complementary experimental apparatuses have been developed, respectively at CETHIL and at CFD Research Laboratory UNSW in collaboration with the DIPTEM. Experiments were performed on both. For these experiments Grashof numbers, based on the channel width and the convective heat flux, are about 10^10. Results that have been obtained constitute an important data base which allows characterizing convective heat transfer. Some concern dynamic boundary conditions which are strongly required for the numerical investigation. First results have been presented concerning the UNSW apparatus (e.g. Ménézo et al. [2007]). The present study consists in a comparison (on a common operating range) among both experiments and numerical investigations focusing on the CETHIL experiments.