Natural convection in an asymmetrically heated vertical channel with an adiabatic auxiliary plate

• Effect of an auxiliary plate on natural convection in an asymmetrically heated channel is studied numerically.
• Hundred simulations are performed to determine the positions of the auxiliary plate that enhance the thermal performance
• Contour maps precise the enhancement rates of the mass flow and the heat transfer for any position of the auxiliary plate
• The flow structure has permitted to explain the observed enhancement or deterioration of thermal performance
• The auxiliary plate could be a simple and cheap tool that controls the mass flow rate in natural ventilation systems

The effect of an auxiliary plate on natural convection in an asymmetrically heated channel is studied numerically in laminar regime. The computational procedure is made by solving the unsteady two dimensional Navier–Stokes and energy equations. This nonlinear system is integrated by a finite volume approach and then solved in time using the projection method, allowing the decoupling pressure from velocity. More than hundred simulations are performed to determine the best positions of the auxiliary plate that enhance the induced mass flow and the heat transfer rate for modified Rayleigh numbers ranging from Ram = 102 to Ram = 105. Contour maps are plotted and then used to precise the enhancement rates of the mass flow and the heat transfer for any position of the auxiliary plate in the channel. The numerical results (velocity, pressure and temperature fields) provide detailed information about the evolution of the flow structure according to the geometry considered in this study. In addition, they permit to explain why the mass flow rate and Nusselt number are enhanced for certain positions of the auxiliary plate and are on the contrary deteriorated for others.