A FILM MODEL FOR FREE-CONVECTION OVER A VERTICAL POROUS PLATE WITH BLOWING OR SUCTION

A film model is described for free convective heat transfer and fricti on in the presence of wall suction or injection. The analysis yields a thermal correction factor, which appears to be the classical (Ackerma nn) expression, and a novel friction correction factor, derived here f or the first time. Both correction factors are applied to free convect ion along a vertical flat porous plate for values of the Prandtl numbe r of 0.73, 1 and 7. Subsequently, the film theory predictions are comp ared with the numerical and asymptotic results of a boundary layer ana lysis, performed by previous investigators. On the basis of this compa rison, a modified correction factor is proposed which correlates excel lently with the results of the boundary layer analyses.