NATURAL-CONVECTION IN A SQUARE ENCLOSURE HEATED PERIODICALLY FROM PART OF THE BOTTOM WALL

Transient heat transfer by laminar natural convection in a square cavity partially heated from below is studied numerically using a finite difference procedure. The temperature of the heating element is uniform, but its magnitude varies sinusoidally with time, oscillating about a fired mean value. The opposite cold wall is maintained at a constant temperature, while the rest of the bottom wall and the vertical walls are adiabatic. The transient solutions obtained are all periodic in time (0.02 less than or equal to tau less than or equal to infinity). Parameters of the problem are the enclosure aspect ratio (A = 1), dimensionless length of the heating element (0.125 less than or equal to B less than or equal to 0.5), position of the heating element (0 less than or equal to epsilon less than or equal to 0.25), dimensionless amplitude of the heating element temperature (0 less than or equal to a less than or equal to 0.4), Prandtl number (Pr = 0.72), and Rayleigh number (10(5) less than or equal to Ra less than or equal to 2 x 10(6)). Heat transfer and effects of various parameters on the flow and temperature fields are studied.