Experimental investigation into the positive effects of a tri blade like windbreak wall on small size natural draft dry cooling towers
Cooling efficiency of heat exchangers in conventional large natural draft dry cooling towers (NDDCTs) is often affected by crosswind. In our previous work, it was verified that the crosswind influence is more significant on short NDDCTs (height <30 m) with horizontal heat exchangers than on large towers at a same wind speed. A new tri blade like windbreak has been proposed in the tower base to improve the cooling performance. In this paper, a following up experimental study on a 1:12.5 scaled NDDCT equipped with a novel round heat exchanger model is reported. Instrument measurements were made on the air temperatures and velocities as well as the heat rejection rates on the scaled cooling tower model with and without the windbreak wall, and the influences of three wind attack angles (0deg, 30deg, and 60deg) with respect to the windbreak wall were particularly investigated. The overall heat transfer performance of the cooling tower was found sensitive to the attack angles. The study verified that the cooling performance is improved most if the tri blade like windbreaks placed in the attack angle of 0deg. The experiment results qualitatively agreed with the predictions of the two 3D CFD models, the 15 m tall prototype and the 1.2 m tall tower model.