The Convection Boundary Layers Thermal Boundary Layer (Cont'd) Free stream 6,) Thermal boundary layer 一T,≠T0 T Heat Flux 0 Heat flux analogous to shear stress in velocity boundary layer Heat flux proportional to the temperature gradient at the surface, AND since u(y=0)-0,energy transfer to/from fluid occurs by conduction only! wall at temperature fluid thermal gradient conductivity y=0 Since thermal boundary layer gets larger along x direction,the temperature gradient changes with x,and therefore Heat Transfer Su Yongkang School of Mechanical Engineering# 13 Heat Transfer Su Yongkang School of Mechanical Engineering The Convection Boundary Layers Thermal Boundary Layer (Cont’d) Heat Flux • Heat flux analogous to shear stress in velocity boundary layer • Heat flux proportional to the temperature gradient at the surface, AND since u(y=0) =0, energy transfer to/from fluid occurs by conduction only! • Since thermal boundary layer gets larger along x direction, the temperature gradient changes with x, and therefore Ts ≠ T∞ fluid thermal conductivity wall temperature gradient ____________________ =0 ∂ ∂ ′′ = − y s f y T q k