Effect on the Local Heat-Transfer Coefficient in a Pipe of an Abrupt Disturbance of the Fluid Flow: Abrupt Convergence and Divergence of Diameter Ratio 2/1

Abstract

The effect of an abrupt convergence, diameter ratio 2/1, on the local heat-transfer coefficient for water flowing in a straight pipe has been determined for Reynolds numbers from 800 to 100,000 in the smaller pipe, which had an internal diameter of 1 inch. The pipe was heated by the longitudinal passage of a heavy direct current through the wall. The variation in local coefficient, which was comparatively small, is presented and discussed; it does not differ greatly from the variation found in the entry regions of pipes under more normal entry conditions. The effect of an abrupt divergence, diameter ratio 1/2, has also been determined for Reynolds numbers from 3,700 to 45,000 in the larger (2-inch) pipe. The variation in local coefficient was considerable.