A perturbation technique to solve conjugated heat transfer problems in circular ducts

Abstract.A simple perturbation technique is used to reformulate the energy equations, which describe the transient thermal behavior of a radially lumped conjugated heat transfer problems in circular ducts of finite wall thickness. This technique is used to eliminate the coupling between the fluid and solid-wall energy equations when the normalized temperature difference between the fluid and the solid wall is small-perturbed quantity. The importance of this technique is demonstrated comprehensively in the example. It is found that there are three parameters that control this technique.