Simulation of a Counter-Flow and Cross-Flow Cooling Tower by the Stepwise Integration Method

Abstract

The stepwise integration method is an approximation method for determining the water temperature in the fill layers for a counter-flow cooling tower and in the fill cells for a cross-flow cooling tower. Accordingly, it can be assumed that the mean driving force in each layer is a constant and the water temperature difference of each layer is equal to the cooling range divided by the required number of layers. Thus, the stepwise integration method can predict the volumetric heat transfer coefficient, the outlet temperatures of the water and air passing through the cooling tower and also determine the operating points of a cooling tower with a known value of KaV under a given approach. However, the stepwise integration method can also simulate and plot the approach curve by condition 1 ( given the inlet and outlet temperatures of water), and the characteristic curve by condition 2 ( given a value of KaV for the entire fill). In a cross-flow cooling tower, where the value of KaV for the entire fill, the flow rates of the entering air and water, the inlet dry bulb and inlet wet bulb temperatures and the hot water temperature are known, it is possible to predict the outlet water temperature by the stepwise integration method. In addition, the stepwise integration method can be used to simulate and plot the approach curve using condition 1 and the characteristic curve using condition 2.