Single-phase heat transfer and flow characteristics of micro-fin tubes

Single-phase heat transfer and flow characteristics of micro-fin tubes were investigated experimentally. Four different tubes were used to obtain experimental heat transfer coefficients and friction factor with varying Re (3000-40,000) and Pr (4-7). The Re affected the friction factor in the fully turbulent region for test tubes. The micro-fin tubes show an earlier achievement of the fully rough region which starts at the Re-epsilon of 70 for roughened surface tube. Proposed empirical correlations showed relatively improved predicting performance and their mean deviation and root mean square deviation were less than 6.4%. From the point of efficiency index the tube with higher relative roughness and smaller spiral angle showed better heat transfer performance than the tube,with larger spiral angle and smaller relative roughness. Heat transfer area augmentation was the main contributor to the efficiency index. (c) 2004 Elsevier Ltd. All rights reserved.