The rain zone is one of the most important area in the wet cooling tower. It contains about 20% of the overall heat and mass transfer of the whole wet cooling tower. The air drag in the rain zone accounts for more than 50% of that in the entire wet cooling tower. However, the study of the rain zone is always a difficulty in the cooling tower research. This is because there exist numerous raindrops in the rain zone, the size distribution and the motion mechanism of the raindrops are very complicated. Therefore to carry on the study of the rain zone, this paper conducts the field test of the raindrops measurement in the wet cooling tower for the first time. The velocity distribution and the size distribution of the droplets in the rain zone are explored and analyzed. The scattering techniques of the drop sizing measurement are used firstly in the cooling tower research. The optical disdrometer which is often used in the meteorology is employed. A stretchable jib arm with full length of 20 m is designed by the author to equip the optical disdrometer. The velocity and the diameter of the raindrops are firstly investigated in different positions in the rain zone. The characteristics of the droplets size distribution is revealed, that is the raindrops have almost the same diameter distribution in different positions in the rain zone. At last, the mechanism of droplets motion and its impact on the size and velocity distribution are analyzed and discussed.
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .