In the present study, the concept of the spraying-type cooling towers is discussed, and then the preliminary design procedure of spraying-type cooling towers is provided. The spraying-type cooling towers are characterized by the spray-induced air draft to exchange heat and mass transfer between water (to be cooled) and the ambient air. In other words, instead of installing a large fan in the system, an array of spray nozzles is placed at the air-intake to induce the external air for cooling of water. Thus, the spraying-type cooling towers have a merit of low noise and vibration compared to the forced draft cooling towers with a large fan.
Generally, the main parameters to be considered in the design procedure are the specifications of the unit nozzles, configuration of the nozzle arrangement, injection pressure and temperature of water, and the ambient-air temperature and humidity. Once the specifications of the nozzles and their arrangements, and the injection conditions are given, the spray performance (such as drop size distribution and the spray pattern) can be decided. Then the amount of the air-draft is determined from the momentum exchange between the spray drops and the ambient air. At the same time, the change of the drop temperature can be determined from the heat and mass transfer between the spray drops and the ambient air. A simplified analysis has been performed to estimate the change of the water(drop) temperature with the axial distance from a nozzle for various injection and ambient air conditions. In the latter part of the present study, the performance of the spray from a unit nozzle was studied experimentally, and also the spray(drop) temperature was measured along the axial direction by changing the injection and the ambient air conditions. Fan spray nozzles widely adopted in the spraying-type cooling towers were used in the experiments. The analytical results reasonably agree with the experimental ones. Finally, the validity of the simplified analytical approach for the preliminary design of the spraying-type cooling was discussed along with the future works.
