Numerical analysis of natural convection in air in a vertical convergent channel with uniformly heated conductive walls

Natural convection in air in a convergent channel with the two principal flat plates at uniform heat flux with finite thickness and thermal conductivity was numerically investigated. Laminar, two-dimensional steady-state conditions were assumed. An extended computational domain was adopted, which allows to take into account the diffusion by both momentum and energy outside the channel. A comparison with experimental data was carried out. Stream function and temperature fields are presented. Average Nusselt numbers were evaluated and presented. Temperature profiles are strongly affected by the convergence angle at low Rayleigh numbers. At the lower minimum gap, streamlines and isotherms show a low pressure region in the channel due to a choked flow in its upper end. Numerical values of the Nusselt number are in good agreement with experimental results.