Field test study on water droplet diameter distribution in the rain zone of a natural draft wet cooling tower

A field test study was conducted on a natural draft wet cooling tower to quantitatively investigate the water droplet diameter distribution in the rain zone for the first time. A test rig with alterable test positions was designed and constructed. The test time for each set of data is 300 s. The test data are presented in the form of a number ratio (R) with water droplet diameter (d). The results manifest that d is scattered between 0.312 mm and 15 mm, regardless of the crosswind velocity. Under low crosswind speed conditions, R has nearly an identical distribution pattern along the circumferential and radial directions, which are relatively large at d = 0.812 mm and 5.5 mm, respectively. As the droplets move from the position of c(1)r(1)h(1) to c(1)r(1)h(3), the R at d > 3.75 mm increases significantly, and the difference in R at d = 0.812mm and d = 5.5 mm increases from 0.7% to 4.1%, respectively. When the crosswind speed is relatively high, the R is basically consistent at different height positions and shows a difference on the windward side, leading to a noticeable increase in R at d < 3.25 mm. For engineering applications, the cumulative distribution of water droplet diameter is further obtained.