Prediction of flow and heat transfer in internally finned tubes

The analysis of fully developed turbulent flow and heat transfer in tubes with straight fins was presented using a special version of the mixing length model. The model takes account of the proximity of both fin surfaces and the tube wall as well as the gradients in the radial and circumferential direction. The adjustable constant in the model was determined after comparisons with experimental data for friction factor and Nusselt number. The numerical predictions were in good agreement with experimental results. The analysis of fully developed laminar flow and heat transfer in tubes with twisted fins consisted of a new computational technique based on the employment of a transformed coordinate system which follows the twisted fin. Due to the periodicity of the secondary flow, the set of finite difference equations were solved by employing cyclic tri-diagonal matrix algorithm.