The Convection Boundary Layers Thermal Boundary Layer (Cont'd) Heat Flux (Cont'd) Using Newton's law of cooling: q"=h(T,-T) We obtain k,aT/ay h= Ts-T While 8 increases with increasing x,temperature gradients in the boundary layer must decrease with increasing x. Accordingly,g,and h decrease with increasing x. Heat Transfer Su Yongkang School of Mechanical Engineering# 14 Heat Transfer Su Yongkang School of Mechanical Engineering The Convection Boundary Layers Thermal Boundary Layer (Cont’d) Heat Flux (Cont’d) • Using Newton’s law of cooling: We obtain • While δ increases with increasing x, temperature gradients in the boundary layer must decrease with increasing x. • Accordingly, and h decrease with increasing x. ( ) = − ∞ q ′′ h Ts T ∞ = − − ∂ ∂ = T T k T y h s y f 0 / s q ′′