Turbulent heat transfer and pressure drop in plain tube bundles

Abstract

The influence of turbulence intensity on heat transfer and pressure drop in tube bundles was measured in an open wind tunnel. The bundles consisted of one to three rows of plain tubes with in-line and staggered tube arrangements. The vertically arranged tubes were heated by saturated steam, condensing inside, and cooled outside with air in cross-flow. The turbulence intensity behind different grids varied in the air stream between 0.8% and 25%, and the air-side Reynolds numbers ranged from 1.5 × 10 4 to 1.5 × 10 5. The enhancement of the heat transfer coefficients for the bundles is due to an increase in the level of turbulence and also to a decreasing number of rows. The increase in the Nusselt number is about 42% for a single row and about 14% for a tube bundle with three rows. From the pressure drop experiments it follows that over a wide range of Reynolds numbers the drag coefficient is almost independent of the inlet turbulence intensity. In this paper the experimental results for single rows and for bundles with three rows are presented. The influence of the transverse and longitudinal pitch to diameter ratio on heat transfer and pressure drop is discussed.