Free convection generated in an enclosure by alternate heated bands. Experimental and numerical study adapted to electronics thermal control

The present work relates to the thermal control by natural convection of the electronic assemblies contained in confined spaces. We have performed a numerical and experimental study to determine the thermal behaviour in a cavity where the electronic assembly is a wall made of discrete hot sources under dynamic operation. The treated cavity is an air-filled cube that consists of two active opposing walls connected by a channel. The channel is adiabatic and the two active walls are the responsible of the natural convection flow inside the cavity. The cold wall is maintained isothermal at temperature Tc. The second active wall consists of 5 bands of which 3 are heated and maintained at Th, separated by 2 other adiabatic bands. The active walls can be vertical but they can also be tilted an angle α respect to the gravity direction. Calculations in steady-state regime are carried out by means of the finite volumes method. The dynamic and thermal aspects are examined for several configurations obtained while varying the difference of temperatures ΔT = Th − Tc and the inclination angle of the cavity. This study covers a wide range of Rayleigh number Ra going from 103 to 3 × 108 and inclination angles α between 0° and 360°. The results can be applied in particular to the field of airborne electronics, which is affected by specific thermal conditions.