Optimum wall-to-wall spacing in solar chimney shaped channels in natural convection by numerical investigation

A numerical study on the laminar and turbulent flows induced by natural convection in channels, with solar chimney configuration, for a wide range of Rayleigh number, several values of the relative wall-to-wall spacing and different heating conditions has been performed. The low-Reynolds k–ω turbulence model has been employed to simulate the turbulent cases. Numerical results for the average Nusselt number and the non-dimensional induced mass-flow rate have been obtained for values of Rayleigh number varying from 105 to 1012 for symmetrically, isothermal heating. For this heating condition, a correlation for the thermal optimum aspect ratio has been presented. The sudden change reached in the flow pattern for given conditions drives to obtain a different behavior of the optimum aspect ratio that maximizes the mass-flow rate with respect to the thermal optimum aspect ratio.