In this study, the effects of dimensionless geometric parameters including, curvature ratio and torsion on pressure drop and heat transfer in coiled tubes were analyzed. In the experiments, hot water was passed through coiled tubes, which were placed in a cold bath. From measured temperatures, pressures and flow rates the Nusselt number (Nu) and friction factor (f) values at various Reynolds number were found for various coil geometries. Heat transfer augmentation is obtained at the expense of increase in pressure drop caused by curvature of the pipes. Hence, a performance analysis is essential to found that the method used to enhance the heat transfer rate is efficient from energy point of view or not. For this purpose, thermal–hydraulic performance ratio (PR) for coiled tubes with different geometric parameters was evaluated. In addition, empirical correlations were proposed for estimating the PR in the coiled tubes and their constants were determined by means of the genetic algorithm (GA) method.
