CONJUGATE HEAT TRANSFER FROM A HOLLOW CYLINDER
The transient heat transfer from a hollow cylinder which is suddenly subject to a uniform stream is investigated numerically. The hollow cylinder is impulsively heated to a constant temperature at the inner wall. The Navier-Stokes and the energy equations with the Boussinesq approximation are discretized in space by use of the Finite Element method. The resulting system of time dependent ordinary differential equations is solved by use of a finite difference scheme. The numerical results for this conjugate problem show that the local Nusselt number Nu increases rapidly and uniformly along the cylinder outer wall from zero to a maximum at time t*. At time t* Nu becomes nonuniform and gradually decreases to steady-state values. Nu increases with the Reynolds number only after t*. t* can be reduced by decreasing the fluid to solid diffusivity ratio. Nu can be greatly enhanced by increasing the solid to fluid conductivity ratio. The increase in the same ratio also makes the difference in Nu at the front and rear stagnation points more prominent.