Daily and annual variations in ambient air wet-bulb temperatures

Wind velocities, wind directions, wet and dry-bulb temperatures are available from data collected by the U.S. Weather Bureau or the U.S. Military Forces covering a wide range of chronological periods. Sometimes information can be obtained from weather stations located at nearby airports. 

Once the heat load is known and the wet-bulb temperature established, the selection of hot and cold water temperatures and gpm flow help to determine 

The selection of the cooling range depends on process characteristics and requirements, as well as the type of cooling tower under consideration. In general, cooling ranges are divided into three categories  

By definition, approach is the temperature difference of the cold water temperature leaving the tower and the wet-bulb temperature of the ambient air entering the tower. Once the wet-bulb temperature and range have been computed, the establishment of the approach fixes all the operating temperatures of the tower fluids. 

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Figure 5.8 Daily and annual variations in ambient air wet-bulb temperatures.

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