EVALUATION OF TURBULENCE MODELS FOR NATURAL AND FORCED CONVECTION FROM FLAT PLATES

Because forced and natural convective flows over relatively wide flat plates have been widely studied, there are many empirical equations available to estimate the heat transfer rates in such situations. However, it is not clear which turbulence model should be used when numerically calculating the heat transfer rate in situations involving laminar, transitional, and turbulent flows. Furthermore, because of the differences among the results given by the various available empirical correlation equations, the selection of a turbulence model and the estimation of the accuracy of numerical results can be rather difficult. Laminar, transitional, and turbulent natural and forced convective heat transfer from isothermal and constant surface heat flux plates has been considered. It has been assumed that the flow is steady, and symmetrical about the center plane of the plate. The governing equations have been numerically solved using the commercial CFD code FLUENT. Results have only been obtained for a Prandtl number of 0.7. Rayleigh numbers between 10(6) and 10(12), heat flux Rayleigh numbers between 10(7) and 10(15), and Reynolds numbers between 10(3) and 10(7) have been considered. Numerical results for natural and forced convective flows have been obtained using six turbulence models and the numerical results have been compared with the results given by existing empirical equations in the different flow regions considered. These available data made it possible to establish new reliable correlations for natural convective heat transfer in transitional flow regions.