Nusselt number for a prescribed geometry hL f(x,Rex, Pr) Lo oca khk f f(re, Pr) Average dP (For a prescribed geometry is known) =o Many convection problems are solved using Nusselt number correlations incorporating Reynolds and prandtl numbers The Nusselt number is to the thermal boundary layer what the friction coefficient is to the velocity boundary layer ou dP x Re Re L dx Heat Transfer Su Yongkang School of Mechanical EngineeringHeat Transfer Su Yongkang School of Mechanical Engineering # 6 Nusselt number for a prescribed geometry (For a prescribed geometry, is known)  Many convection problems are solved using Nusselt number correlations incorporating Reynolds and Prandtl numbers • The Nusselt number is to the thermal boundary layer what the friction coefficientis to the velocity boundary layer. ( ) (Re ,Pr) Average k hL ,Re ,Pr Local k hL f * f L L Nu f Nu f x = = = = * * dx dP         =   =  = = * * * 0 * * 2 ,Re , Re 2 2 dx dP f x y u V C L L y s f  