The influence of windbreak wall orientation on the cooling performance of small natural draft dry cooling towers

Abstract

While crosswind has a negative influence on natural draft dry cooling towers (NDDCTs) of all sizes, the influence may be fatal for short towers (height < 30 m) proposed for geothermal or solar thermal power plants. In a previous paper, the authors demonstrated the potential for tri-blade-like windbreak walls not to only maintain but significantly improve the short tower cooling performance. The effect of crosswind attack angle (windbreak walls orientation) was not examined in that paper. The present paper investigates that effect for a 15 m-high small-size NDDCT with horizontally-arranged heat exchangers. 3D CFD models with different wind attack angles (0°, 10°, 20°, 30°, 40°, 50°, and 60°) are set up and computed at different crosswind speeds. The results indicate that the way the cooling tower performance varies with the crosswind speed is highly sensitive to the wind attack angles. At attack angles of 0° and 60° the cooling performance is improved by windbreaks over the entire crosswind speed range investigated. Other attack angles lead to unfavourable effects at certain wind speeds. The differences are related to the turbulent airflow field in the tower bottom. The results suggest that the tri-blade-like windbreaks placements always with one symmetry axis alignment with the dominant crosswind direction. The findings could be used to determine the windbreak installation angles with respect to the most frequent direction(s) of the ambient wind in a given district.