Heat transfer and pressure drop in large pitch spirally indented tubes

摘要

Heat transfer and pressure drop experiments were performed with water, at atmospheric pressure in the Prandtl number range 3.6 to 8.8, flowing turbulently in spirally indented tubes for heat exchanger application. Large pitch geometries were studied which minimized pressure drop. The pitch to rib height ratio was in the range of 23.7 to 120 which is beyond the range ally considered in previous investigations. Four tubes were tested with rib height to diameter ratios of 0.0075, 0.021, 0.038, and 0.0 (plain). The tubes were tested in a counter flow heat exchanger arrangement which produced results directly applicable to heat exchanger analysis. A data reduction technique was developed that is applicable to an arbitrarily augmented tube, and it was verified with the plain tube data. Heat transfer and pressure drop results from the spirally indented tubes were compared to extensions of correlations for similar geometries and to limited data available at large pitches.