Experimental study on the effects of a tri-blade-like windbreak wall on small size natural draft dry cooling towers

Abstract

Cooling efficiency of heat exchangers in conventional large natural draft dry cooling towers (NDDCTs) is often affected by crosswind. In the authors’ previous work, it was proved 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, and a new triblade-like windbreak was proposed and analysed through CFD method only. The numerical models have not been validated by testing data yet. Therefore, an experiment on a 1:12.5 scaled NDDCT equipped with a novel round heat exchanger model was carried out and is presented in this paper. The study obtained the real measurements on the air temperatures and velocities as well as the heat rejection rates in the scaled cooling tower model with and without the windbreak wall. The influences of three wind attack angles (0°, 30°, and 60°) with respect to the windbreak wall were investigated. The angle was found sensitive to the overall heat transfer performance of the cooling tower. The study found that the cooling performance is improved most if the tri-blade-like windbreaks placed in the attack angle of 0°.The experiment results agreed with the predictions of the two 3D CFD models, the 15 mtall prototype and the 1.2 m-tall tower model, so that verified the validity of the previous CFD modelling