Single-phase heat transfer in micro-fin tubes

Abstract

Micro-fin tubes are typically used for tube-side condensation and evaporation. This study provides heat transfer and friction characteristics for single-phase flow in single-grooved and cross-grooved micro-fin tubes. Data were taken for turbulent flow with 0.70 ⩽ Pr ⩽ 7.85 for three single-grooved and three cross-grooved geometries. The cross-grooved tube provides higher performance than the best single-grooved tube. A key element of this work was to determine the Prandtl number dependency and the effect of surface geometry on the Prandtl number dependence. The heat transfer characteristics were determined as functions of the ‘roughness Reynolds number’ using the heat-momentum transfer analogy proposed by Dipprey and Sabersky. The observed Prandtl number exponent ( n = 0.56-0.57) agrees well with reported work on different two-dimensional roughness geometries. The present single-phase correlations should be useful in developing correlations to predict the heat transfer coefficient for forced convection condensation in single-grooved and cross-grooved micro-fin tubes.