Numerical simulation of natural convection heat transfer in open space between two horizontal circular planes

Numerical simulations are conducted for the natural convection heat transfe r in a narrow gap between two horizontal plates in air. The lower plate is an infinite plate with a circular heating zone. The upper one is the bottom of a vertical cylinder, which is placed right above the circular heated pl ate and kept at room temperature. A set of Navier-Stokes equations and an energy equation are analyzed for a variety of combinations of gap clearance and Rayleigh number. The calculate d average heat transfer are shown to be in good agreement with the experime ntally obtained ones reported in the previous paper. From the obtained isot herms, stream lines and local Nusselt numbers, it is found that two types o f convection appear in the gap space according to the conditions of Rayleig h number and gap clearance : one is a simple convection due to the single r enewal flow which replaces heated air with ambient air and the ether is a c ombined convection due to several vortex flows and the renewal flow. Furthe rmore, it is also found that the flow rate of each flow controls the rate o f heat transfer from the limited area which is covered by each flow. From t his fact, the validity of the previously proposed heat transfer correlation is briefly discussed.