"General Expression for Laminar Forced and Natural Convection Heat Transfer from Isothermal Flat Plates for all Prandtl Numbers"

Abstract: The conventional correlation equations for forced and natural convection boundary-layer flows over isothermal flat plates are shown to collapse into a single simple expression which directly relates the dimensionless wall temperature excess to a new Prandtl number function which is applicable for the full range of the Prandtl number from zero to infinity. The dimensionless wall temperature excess is defined with respect to the unknown area-mean wall heat flux, the thermal conductivity of the fluid, the given wall temperature excess and a new length scale which is related to the plate length, the fluid thermal diffusivity and the maximum fluid velocity within the respective boundary layers. The conventional forced and natural convection dimensionless groups: Nusselt, Reynolds, Peclet, Grashof, Rayleigh and Boussinesq numbers do not appear in the proposed simple general correlation equation. The new formulation allows the forced and natural convection heat transfer results to appear on the same graph as dimensionless temperature excess versus Prandlt number functions. This shows that the two physical phenomena are closely related; this is not apparent from the conventional correlation equations.

AIAA 28^th Annual Thermophysics Conference, Orlando, FL, July 6-9 (AIAA Paper No. 93-2750)

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