Experimental natural convection in vertical cavities with adiabatic extensions: the effects of the distance between symmetrically or asymmetrically heated staggered walls

Due to modern engineering applications such as solar collectors, passive ventilation of buildings, cooling of electronic equipment, and nuclear reactors, there is a renewed interest in studying natural convection in vertical channels. This experimental work aims to evaluate the heat exchange inside open-ended cavities by varying the distance “s” between the walls, considering the presence or absence of adiabatic extensions that follow or precede parts heated both symmetrically and asymmetrically. The test section consists of two walls, called I and II, composed of three modules that can be assembled in different ways: two of them are adiabatic panels, while the third is a plywood frame on which the heater, aluminium plate, thermocouples and thermal insulation are fixed. Let L be the height of the metal plate and let H be the overlap between the plates of the two walls, the configurations studied in this work are for H/L=1, H/L=0.3 and H/L=0.1 with and without adiabatic extensions, in the case of heating of a single wall, symmetric heating and asymmetric heating with imposed thermal powers. The Rayleigh number is 8,2·10^4≤Ra𝐿≤2,2·10^6. Results show optimal configurations maximizing the Nusselt number as a function of distance s, H/L ratio and the presence of adiabatic extensions.