Experimental study on the fouling and heat transfer characteristics of enhanced tubes used in a cooling tower water system with the actual water quality

Abstract

Accelerated fouling tests using water conditions more severe than actual project have been proven that it could not truthfully reflect the fouling development. To fill the research gaps of long-term fouling tests, three sets of continuous long-term fouling tests on eight enhanced tubes and one plain tube were performed over a duration of 86–143 days to explore the deposition behavior of the combined fouling. In this study, a decoupling method was presented to compare the heat transfer ability of different test tubes in different operation conditions. Detailed mechanisms of the effects of water velocity and tube geometries on the combined fouling process for enhanced tubes were revealed. Results showed that increased water velocity causes the introduction period of the fouling process to be reduced continuously. In addition, the asymptotic fouling resistance variation curve presented a downward parabola with increased water velocity. For one enhanced tube, the asymptotic fouling resistance decreased with the increase of water velocity from 0.9 m/s to 2.4 m/s. However, the plain tube presented asymptotic fouling resistance that first increased, and then, it decreased when the water velocity rose from 0.9 m/s to 2.4 m/s. In order to evaluate the performance of enhanced tubes when considering heat transfer, fouling, and pressure drop, a comprehensive performance evaluation criteria (CPEC) was proposed, and its calculation correlation was developed with an average error of 7.06%.