Free-convective heat transfer within a differentially heated vertical plane during additional heat supply through a bottom wall

This work presents results of a numerical investigation of the structure of flow and heat exchange in a vertically closed interlayer with various relative heights $A=H/L=4$–$16$ during variation in heat supply to its bottom. The vertical walls were isothermic; top wall, bottom wall, heat flow was supplied uniformly. The nonstationary Navier–Stokes equations were solved numerically in the two-dimensional formulation for the laminar flow. At small Rayleigh numbers ($\mathrm{Ra}\approx10^3$), when conductive heat transfer prevails within the interlayer, the effect of heat supply from below results in a change of heat transfer only in an immediate vicinity of the bottom. As the Rayleigh number and supplied heat increase, flow destabilization is observed, which results in strong heterogeneity of the density of heat flow along the wall height. At the same time, the heat flow at the hot vertical wall at defined Rayleigh numbers and heating from below may change the sign to the opposite one.