Specification List for Cooling Towers

1 A cooling tower has a cross-sectional area of 25 X 25 ft. The total heat load to the unit is 27,500,000 Btu/hr. The locality has a 5% wet-bulb temperature of 75°F. Water exits the tower with a 12° approach to the wet-bulb temperature (i.e., 87°F).The hot process water enters the tower at a temperature of 125°F, and the water equivalent to this range is 1800 gpm. The systems fan capacity is 150,000 cfm (a) Determine the number of diffusion units that the tower must be capable of performing to meet process requirements (b) the tower manufacturer provided the following data for overload and underload conditions for the tower  

Determine how much water the tower can provide from 115°F to 85°F when the wet bulb is only 70°F. (Hint a trial-and-error solution must be used to match conditions on a plot of KaV L versus L G). 

0-ft-diameter (inside diameter) tower has a packed section 15 ft tall. The packing material is 3-inch Berl saddles. Water (50 gpm feed to the tower) is to be cooled from 128°F to 87°F. Approximately 4000 cfm of air is used to cool the water. The air has a dry bulb of 83°F and a wet bulb of 77°F. 

In a field test at a gas loading of 1500 lb/(hr)(ft2), a diffusion coefficient of 380 lb/(hr)(ft2)(lb/lb) was obtained. Determine the temperature to which the same tower could cool 7500 cfm to gas if the packing height were increased to 20 ft. Repeat the problem for 30 ft of packing height. 

3 A direct-contact gas cooler system operates as follows Approximately 35,000 lb/hr of bone-dry air is passed over hot trays. The air is heated from 150°F to 325°F as it passes over the trays. It exits from the unit with a due point of 105°F. The hot air is sent to a direct-contact cooler, where its temperature is reduced back to 150°F. During the cooling stage, the air is dehumidified with water that is heated frpm 75°F to 105°F. The unit is rated at 3.5 inches of water pressure drop (a) Determine the number of diffusion units needed for this operation and (b) Establish the required dimensions for the direct-contact cooling tower (Hint Use standard low-pressure-drop data from the literature. Some of the older literature give pressure drop data for simple fill. See Sherwood, T. K. and C. E. Reed [6]. 

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