Air flow distribution prediction and parametric sensitivity analysis of horizontal-arrangement parallel-path hybrid cooling towers

Abstract

Horizontal-arrangement parallel-path hybrid cooling towers (PPHCTs) are advantageous owing to their low construction cost, high cooling capacity, and broad application prospects. The dry and wet sections of these towers have separate air inlets but share the same air outlet, which is equipped with a fan. Air is delivered to the tower by the fan. The air flow distributions in the two sections mainly determine their respective cooling capacity and the entire tower cooling capacity. Traditional model usually adopted assumed or experimental air flow rate, which leads to low prediction efficiency. To solve this problem, in this study, an air distribution model considering fan performance curve and system resistance curve is proposed for calculating the exact air flow rate based on the configurations of the tower. In addition, the influence and contribution ratio of row numbers and transversal pitch in wet and dry sections on the air flow rate in each section is analyzed, which is beneficial for optimal design in the engineering application. Adding more rows or reducing the transversal pitch in the wet and dry sections increased the pressure drop on the same side, pressure drop on the other side, and overall pressure drop. Increasing the flow resistance coefficients in any of the wet or dry sections decreased the air flow rate on the same side and the overall air flow rate, while the air flow rate on the other side increased. The number of rows in the dry section significantly affected the air flow rate ratio between the dry and wet sections and the overall air flow rate. The contribution ratio of the number of rows in the dry section to the overall air flow rate was 76.75%, while to ratio of air flow rate between the dry and wet sections was 61.73%. The results of this study can be used for precise performance prediction and optimal design for the PPHCTs.