Analytic Prediction of the Friction and Heat Transfer for Turbulent Flow in Axial Internal Fin Tubes

An analytic model is developed to predict the friction factors and Nusselt numbers for turbulent flow in axial internal fin tubes. The present model uses the Law of the Wall and applies the logarithmic universal velocity and temperature profile to the interfin and core regions of the flow. The fin shape is assumed trapezoidal, and the fin parameters such as fin height, fin root thickness and fin tip thickness are determined from the tube dimensional data. Theoretically based friction and heat transfer equations are developed for internally finned tubes in an algebraic form. The analytic model predicts Carnavos friction data for 11 axial internal fin tubes within ± 10 percent, and heat transfer data of air, water, and water-glycol within ± 15 percent when proper velocity and temperature profiles are used.