The adoption of windbreak wall partially rotating to improve thermo-flow performance of natural draft dry cooling tower under crosswind

Abstract

To reduce the adverse effect of crosswind on thermo-flow performance of the natural draft dry cooling tower (NDDCT), a novel type of external flat windbreak walls is introduced. Taking the prevailing wind direction as the symmetry axis, windbreak wall arranged at each flank of the tower is divided into three rotatable columns according to the size of the researched NDDCT, with the rotating angle equal to air inflow deviation angle of nearest cooling delta. Subsequently, using the steady model and half tower simulations after comparison, effects of various combinations of the rotatable columns were revealed based on the analysis of velocity and temperature fields in and around the tower. At the general wind speeds, wall form of only middle column rotating contributes the largest performance improvement to the tower, which is over 17% at wind speed of 8 m/s, nearly 2.5% larger than that brought by the traditional radial walls. Meanwhile, it was found that outlet water temperatures of the next three cooling deltas at the back of inner column get increased under the optimal wall form. To overcome this problem, porous walls were tested to be applicable, but without overwhelming superiority, compared to the solid walls. In addition, when crosswind gradually deviates from the specified prevailing wind direction, wall form of only middle column rotating is still superior to the traditional radial walls, especially at a small crosswind deviation angle, but the difference between the benefits brought by the two wall forms to the tower is decreasing.