In order to clarify the prediction accuracy of Boussinesq approximation, natural convection in a enclosure with heated and cooled vertical walls is analyzed by CFD technique based on Boussinesq approximation and low Mach number approximation. In the case of ΔT=300℃, the difference of the velocity profile between Boussinesq approximation and low Mach number approximation is great, and about 20% of the maximum velocity in the perpendicular direction. The cause which produces such a difference is mainly due to fact that the density of air in the continuity equation is constant in Boussinesq approximation.
