Effect of Different Flow Regimes on Natural Convection Heat Transfer from a Vertical Plate

In the present study, weak points of all methods until now and the effect of different flow regimes on natural convection heat transfer from a vertical plate are discussed. Furthermore, a new analytical method is developed to calculate natural convection heat transfer from vertical plates which has the potential to be applied to other convex geometries for a wide range of Rayleigh numbers in fluids with any Prandtl number. This method is based on the new concepts of Dynamic Body Gravity and Dynamic Turbulent Functions (DBG & DTF respectively). Also, a new transition criterion from laminar to turbulent flows is introduced and applied in this method. In addition, a correlation is presented to obtain Nusselt for all Rayleigh (Laminar flow - Transition region - Turbulent flow) and Prandtl numbers. Finally, the present results for two isothermal vertical plates and a horizontal cylinder has been compared with the available experimental data. Excellent agreement is found between the proposed model and experimental results in a wide range of Rayleigh numbers with a maximum percentage difference less than ۱۲. This shows that the present model is powerful enough to model natural convectionheat transfer from isothermal convex bodies for a wide range of Rayleigh numbers in fluids with any Prandtl number.

کلیدواژه ها:

Natural (Free) Convection heat transfer ، Isothermal Vertical Plate ، Laminar and Turbulent flow ، Transition Region ، Rayleigh Number and dynamic body gravity and turbulent functions (DBG & DTF)