Thermal conduction through a cool well

Abstract

We study a differentially heated square cavity with inlet and outlet ports at the top of the side walls, quantifying how the effective thermal conductivity changes with the temperature difference across the system. The side walls are insulating, the top surface is kept at a fixed high temperature, and the bottom surface at a fixed low temperature, leading to buoyancy-stabilized flow. We visualize the flow pattern for Reynolds number, Re=1, and Prandtl number, Pr=50, and characterize the heat transfer at the bottom surface using the Nusselt number, Nu, for Re=0.1,1,10 and Pr=1,50. As the Richardson number, Ri, is increased, we observe the formation of a series of system-spanning vortices through the merging of Moffatt eddies growing from the bottom corners of the cavity. We find that the convection, which enhances the transport of heat, is strongly suppressed by increasing the temperature drop. As a result Nu drops by a factor 1–3 depending on the Reynolds number.