Numerical prediction of mixed convection heat transfer in an enclosure

In this article the transport mechanism of laminar mixed convection in a shear and buoyancy driven cavity flow with locally heated lower wall and moving cooled sidewalls is numerically studied using cubic interpolation profile method. This study focused on the interaction of forced convection with natural convection. The heat is locally introduced into the cavity with the dimensionless value of ԑ=1/5 of the non dimensional length of the bottom wall. Studies were conducted on the effect of mixed convection parameter Gr/Re2 (known as Richardson Number) in the range of 0.1-10. The results were illustrated in the form of streamline and isotherms. Three different regions can be detected as the Richardson number is increased: forced convection, mixed convection and natural convection

Local nonsimilarity method for the two-phase boundary layer in mixed convection laminar film condensation

The two-phase boundary layer in laminar film condensation was solved by Koh for the free convection regime and forced convection regime using the similarity method. But the problem on mixed convection does not admit similarity solutions. The current work develops a local nonsimilarity method for the full spectrum of mixed convection, with a generic boundary layer formulation reduced to two specific cases mathematically identical to Koh's formulations on the two limiting cases for either free or forced convection. Other solution methods for mixed convection in the literature are compared and critically evaluated to ensure a high level of accuracy in the current method. The current solution is used to extend Fujii's correlation for mixed convection to the region where the energy convection effect is significant but has been hitherto neglected. The modified Fujii correlation provides a practical engineering tool for evaluating laminar film condensation with a mixed convection boundary laye

Turbulent mixed convection in an enclosure with different inlet and outlet configurations

Given the large impact of the building sector on the final energy demand, special interest lays in passive cooling techniques, such as night ventilation. Unfortunately, a lack of understanding concerning the coupling between the ventilation air and the thermal mass by night stands its widespread application in the way. Therefore, the authors of this paper investigate by computational fluid dynamics turbulent mixed convection cooling in a rectangular enclosure – resembling a night ventilated landscape office. Based on the 2D Annex 20 test case, four different orientations of the inlet and outlet are considered while varying the Archimedes number – ranging from forced to mixed convection. Also the location of thermally massive elements is varied. Locating the inlet and outlet at the top of the room induces the highest convective heat transfer. Meanwhile, locating the thermal mass at the floor has more potential than at the ceiling

NUMERICAL RESULTS OF MIXED CONVECTION FLOW OVER A FLAT PLATE WITH THE IMPOSED HEAT AND ANGLE OF INCLINATION

In this paper, the numerical results of mixed convection flow over a flat plate with the imposed heat and different angles of inclination are established by applying the finite difference method of Crank-Nicolson. We further compare these numerical results with the case of non-mixed convection flow.  The velocity and temperature profiles are decreased when the different values of the Prandtl number (Pr) are increased. Meanwhile, the velocity profiles are increased, when the different values of angle of inclination (alfa) and mixed convection parameter (lambda) are increased. The mixed convection flow case (lambda=1.5) is affected by the external force, so the velocity of convection flow is higher than the non-mixed case (lambda=0)

Thermal Ignition of a Combustible over an Inclined Hot Plate

In this study, the ignition characteristics and the flow properties of the mixed convection flow are presented. Detailed formulations of the forced, natural and mixed convection problems have been discussed. In order to avoid inconvenient switch between the forced and natural convection we introduce a continuous transformation in the mixed convection. We make a comparison between these situations which reveal a good agreement. For mixed convection flow, the ignition distance is explicitly expressed as a function of the Prandtl number, reaction parameter and wall temperature. It has been observed that owing to the increase of the aforesaid parameters, the thermal ignition distance is reduced. Numerical results are illustrated for velocity, temperature, and concentration for different physical parameters. Furthermore, the development of combustion is presented by using streamlines, isotherms and isolines of fuel and oxidizer