THE EFFECTS OF WATER SPRAY COOLING ON COOLER PERFORMANCE

In recent years, summers in the Northeast, as well as in many other re gions of the United States, have reached record high temperatures. The se unusually high ambient temperatures have led to the overloading of power transformer coolers, resulting in the inability of the coolers t o maintain the top oil temperature of the transformer at an acceptable level. A field-tested solution to this problem is the application of water spray onto the tube bundles of the cooler to enhance the heat tr ansfer. Currently, the standard way of applying water to an overheated transformer cooler is to hose it down. This method has always been im plemented without consideration of the spray pattern or quantity of wa ter used, usually resulting in a wastefully high rate of water consump tion. An experiment has been setup to determine the performance of a t ransformer cooler subjected to water spray. This work consisted of the design and implementation of a water spray system to an existing full scale cooling loop representative of those found on actual transformer s. Predictions were also made for the top oil temperature subjected to dry-air cooling and compared with experimental data. The reliability of this model shows that it can be extended for water spray applicatio ns. Heat transfer data were obtained for a range of air velocities and water flow rates on this loop. The experimental results show a signif icant decrease in the top oil temperature of the cooler when water spr ay is applied to the cooler tubes. However, the enhancement was not as significant for water how rates above 4 GPM. Distribution of the wate r spray through the tube bundle were qualitatively made by visual obse rvation.