This paper investigates a set of correlations for friction factor and Nusselt number for turbulent fluid flow in a helically coiled tube. Most of the existing correlations for pressure drop and heat transfer in the coiled tube have been developed based on the results of straight tube correlations. These correlations include different application ranges for parameters such as Reynolds number, Dean number, coil pitch and Prandtl number among others. Depending upon the experimental methods and the theoretical and/or numerical approach, the results obtained by using the (existing) correlations show some degrees of inconsistency over the ranges of parameters. Thus, it is not a simple matter to select proper correlations for analyzing the coiled tube system. Therefore, it is the authors' intension to investigate the existing correlations by introducing Coiling Influence Factors (CIFs) for both Nusselt number and friction factor in the turbulent flow regime. These factors are defined as the ratio of the correlations for the coiled tube over those for straight tube. In order to compare and evaluate, the effects of individual parameters on the CIFs were explicitly investigated in each correlation. Furthermore, employing the method of least-squared curve fit and integrating the individual parametric effects, new proposed correlations for turbulent flow in the helically coiled tube are developed.
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