The effect of condensate inundation on steam condensation heat transfer in a tube bundle

Abstract

Steam-condensation heat-transfer measurements were made using a 5-tube in-line test condenser with an additional perforated tube to simulate up to 30 active tubes. Results were obtained for smooth tubes, wire-wrapped tubes and dropwise-coated tubes. The average outside heat-transfer coefficient for 30 smooth tubes was 0.64 times the Nusselt coefficient for the first tube. A total of eight wirediameter and wire-pitch combinations were tested: 1.6-mmdiameter wire wrapped at 16 mm, 7.6 mm and 4 mm wire pitches, 1 . 0-mm-diameter wire wrapped at 8 mm, 4 mm and 2 mm wire pitches, and . 5-mm-diameter wire wrapped at 4 mm and 2 mm wire pitches. The best bundle performance was obtained when the tubes were wrapped with 1 .0-mm-diameter wire at a wire pitch of 4 mm. This combination resulted in an average outside heat-transfer coefficient for 30 tubes that was 1.15 times the value computed for the first tube using the Nusselt theory. The average outside heat-transfer coefficient for the 30 dropwise-coated tubes was 1.1 times the value of the heat- transfer coefficient for the first tube in the tube bundle. Utilizing either wire-wrapped tubes or dropwisecoated tubes, it is possible to significantly reduce the condenser surface area and overall size.