Deciphering the thermal and hydraulic performances of closed wet cooling towers with plain, oval and longitudinal fin tubes

In this paper we numerically investigate the thermal-hydraulic performances of the closed wet cooling towers (CWCTs) installed with plain, oval, and longitudinal fin tubes in the heat exchanger. Important operational structural parameters such as the flow rates of air and spray water are analysed by combining the discrete phase model with the species transport model of CFD. It is observed that the normal mesh, with a grid number of 43,000, is acceptable, while the realizable model is employed to describe the turbulent flows. The heat transfer coefficient of the fin tube case is the highest when the air flow rate exceeds a critical value, 3.2 kg m(-2) s(-1). However, overall, the oval tube case is recommended due to its high thermal-hydraulic performances and the modest pressure drop. The correlations of the heat and mass transfer coefficients as well as the pressure drop are developed. Furthermore, an uncertainty analysis finds that, the mean of the heat transfer coefficient increases from the plain tube case (1178.2), to the fin tube case (1898.4), to the oval tube case (1943.4). Statistically, the variances in the air flow rate, inlet air temperature, and spray water temperature contribute 52.8-70.6%, 20.4-33.8%, and 9.0-13.4% of the uncertainty, respectively. (C) 2017 Elsevier Ltd. All rights reserved.