Effect of turbulent integral length scale on heat transfer around a circular cylinder placed cross to an air flow

Abstract

The effect of air turbulence on heat transfer around a cylinder is known to be dramatic. Relations based on the intensity of turbulence have been developed to take it into account. However the range of validity of these relations is under debate since they do not take into consideration the scale of turbulence which should also have an effect. This debate is not only theoretical because if the turbulent length scale is important most experiments usually performed at the laboratory scale would probably be disputable in practical conditions. This paper aims at providing some experimental arguments on the effect of the turbulent length scale on the average transfer coefficient value. The effect of a twofold multiplication of this scale from 0.05 to 0.10 m on the heat transfer coefficient has been measured around a circular cylinder placed in the cross-flow of air whose free stream turbulence intensity was 14%. In this range, the effect of the turbulent integral length scale on the average transfer coefficient value is very small and cannot be compared with the dramatic influence of the turbulence intensity.