Condustion-thirough Hollow cylinders velocity and Temperature Boundary Layers Q Velocity Boundary Layer-is developed in the fluid fluid velocit the surface and increases to the bulk fluid velocity u Temperature Boundary Layer-also develops next to =-2xL I dT erature at the fl from T to T T 寻自 R4 Conduction through Hollow Cylinders ( ) kLrr lnT T Q kL T T rr Q ln kL dT r dr Q io i o cond i o io cond Toi T orir cond π π π 2 2 2  − ⇒ = = −   ⇒ = − ∫ ∫   ( ) . dr dT Q cond = − k 2 πrL . dx dT Q cond = −kA kLrr ln R io 2π   = Velocity and Temperature Boundary Layers Velocity Boundary Layer—is developed in the fluid next to the solid surface. The fluid velocity is zero at the surface and increases to the bulk fluid velocity u∞ . Temperature Boundary Layer—also develops next to the surface, where the temperature at the fluid varies from Tw to T∞