Abstract

Mixed convection heat transfer is a process where natural and forced convection happens simultaneously. The effect of temperature difference in natural convection and momentum difference results in mechanical ventilation or pressure difference that result in indoor and outdoor flow. When used in an optimum way, it is one of the newly subjects in HVAC industry which is a prominent example of mixed convection heat transfer. In the present study, first, the laminar flow of natural convection of air in a room with forced convection results in mechanical ventilation and then the calculated results are compared with the results of other researchers. After showing validation of calculations, aforementioned flow is solved as a turbulent flow, using the valid turbulence models RNG , standard  and RSM. To solve governing differential equations for this kind of flow, method of finite volume was used. This method is a special kind of residual weighted method. The results show that turbulence intensity is limited to vertical walls and boundary condition, such that flow in center region enclosure is turbulence and laminar is close to walls. Moreover, it is discovered that when Richardson number increases the maximum local Nusselt decreases; and therefore heat transfer is decreased with increasing Ri number.

Key words: Mixed convection, turbulence, Richardson number, turbulent intensity, wall shear stress, enclosures.