Experimental study of drift deposition from mechanical draft cooling
towers in urban environments
Cooling towers are evaporative devices for removing heat in several applications such as air conditioning in buildings and industrial processes. In this work a comprehensive experiment to study the drift deposition from a mechanical draft cooling tower located in an urban environment was conducted, because of the lack of data in the literature. To predict the area affected by the cooling tower drift deposition is interesting both for its environmental impact assessment, and for the detection of the origin of an outbreak of Legionnaire’s disease. The objective of the experiment was the measurement of the amount of drift water emitted and deposited from the cooling tower. Secondary objectives were to establish a database for use in drift deposition model validation and to analyze the interaction between ambient variables on downwind deposition. These objectives were met by the simultaneous measurement of cooling tower source emission parameters, meteorological variables (registered by a 40 m tall meteorological tower) and drift deposition during four test runs. The sensitive paper technique was employed. Regarding downwind deposition patterns, deposited water and characteristic droplet size decreased as the distance from the tower increased. Variations of 70% of deposited water were found in the measurements at close distances to the tower when the wind velocity level was low. Wind direction also affected the deposition level. Averaged differences of about 45% were observed between the results obtained for the wind blowing from the northwest or the southeast.