Influence of flow velocity and fin spacing on the forced convective heat transfer from an annular-finned tube

Abstract

The evaluation of convective heat transfer from fins to the air has been carried out in the case of annular fins subjected to an air flow parallel to the fin surface. The fin cooling is studied using infrared thermography. The thermal balance in a fin during its cooling process allows us to obtain the expression of the heat transfer coefficient from the temperature time evolution of the fin. Besides, the Particle Image Velocimetry allows us to obain the flow field in the mid-plane between two fins. The influence of the air flow velocity and of the fin spacing on the convective exchanges is studied. The tests have been carried out for Reynolds numbers (based on the shaft diameter and the air flow velocity) between 2 550 and 42 000, for different fin spacings. All the tests are correlated by an equation, expressing the mean Nusselt number on the fin as a function of the dimensionless fin spacing and of the Reynolds number.