Abstract

A laboratory–scale mechanical draft cooling tower equipped with eight sections of perforated inclined plates was designed to determine the effect of operating conditions on the volumetric mass transfer coefficient between water and air. A three–factor, three–level design of experiments was implemented, considering liquid mass flow rate (120, 240, and 360 kg/h), gas mass flow rate (36, 57, and 75 kg/h), and top water temperature (50, 60, and 70 °C). A total of 54 runs were performed, and the global volumetric mass transfer coefficient was calculated by combining energy and mass balances with the Mickley method. The experimental data were fitted to a power–law correlation using multivariable regression. The analysis of variance showed that top water temperature is the dominant factor, followed by liquid mass flow rate, whereas the influence of gas mass flow rate is comparatively small in the studied range. The selected correlation, based on the nominal gas flow rate, achieved a coefficient of determination of 0.869 and a root mean square error of 5.93×10³ kg/(m³h). The volumetric mass transfer coefficient values were found in the range from 4.6×10³ to 6.2×10⁴ kg/(m³h). Vertical temperature profiles of water and air along the column revealed that, for high liquid flow rates, most of the cooling occurs in the lower stages, suggesting that the upper sections are underutilized.