Impact of tower spacing on the performance of multiple short natural draft dry cooling towers for calm conditions

Abstract

Natural draft dry cooling towers (NDDCTs) serve a fundamental role in the deployment of concentrating solar power (CSP) plants. In a multi-tower cooling system, there is a need to be able to position them correctly so that their performance as a group is maximised. To do this, an understanding of the effect they have on one another is needed. Hence, this work investigated the effect of tower spacing on the performance of multiple cooling towers under calm conditions using computational fluid dynamics (CFD) simulations. The applied CFD methods were validated by comparing the current results with real cooling tower results. It found that towers in close proximity would compete for air at their inlet, resulting in distorted velocity and temperature distributions at the radiator surface. Furthermore, the results show that at a tower spacing of less than two tower diameters (2 D) where D is the diameter of the tower, a reduction in the scavenging area between the towers limits the air supply to the towers and this interaction decreases the cooling performance of the towers. The results of three NDDCTs showed that the heat rejection of the middle tower which is surrounded by two towers is highly influenced by the tower spacing and at very low tower spacings, the heat rejection decreases by up to 15%. This new finding holds particular design significance if multiple NDDCTs are deployed on CSP sites that experience a high frequency of calm (no-wind) conditions.