Entrance region heat transfer in a uniform wall-temperature helical coil with transition from turbulent to laminar flow

Abstract

Entrance-region heat transfer to gases flowing in a uniform wall-temperature helical coil was studied experimentally. A novel gradient method of heat transfer investigation was developed based on measurement of the wall internal and external surface-temperature distributions. Runs were made in the range of Reynolds numbers where the flow is initially turbulent upon entering the coil, but laminar downstream where secondary flow develops. No prior measurements of local heat transfer coefficients have been reported for this flow regime or thermal boundary condition. The results indicate a rapid transition to laminar flow and are in satisfactory agreement with a numerical solution for fully developed heat transfer.