The amount of energy that must be removed from die in hot water at the entrance to the tower is equal to the sum of the cooling capacity of connected units, their enthalpy compression and heat absorbed by water on its way to the tower. The water entering the tower is called hot water source. Cooler water outlet from the tower is called the cold, or return water.
As energy and mass are transferred from the water to the atmosphere, the remaining liquid is cooled. Change of temperature experienced water as it passes through the tower is called the range of cooling. Cooling of the range equal to the temperature of hot water in freezing cold water temperature. When a cooling tower is used to serve a single piece of equipment, its range is raising the temperature of the water entering dirough water-cooled condenser. The mathematical difference between the input atmospheres WB temperature and the temperature of the cold water is called the tower approach. As an approach decreases, cold water leaving the tower at temperatures closer to die WB, the temperature of the atmosphere entering the tower.
Cold water can leave the tower at a temperature that is lower than at the entrance into the atmosphere DB temperature.
The mass transfer of water into the atmosphere makes this operating characteristics of the possible. Evaporating moisture draws its latent heat from the remaining liquid. Each unit of energy used for conversion of water into steam, the state reduces the temperature of the remaining amount of water. Therefore, the temperature of the water leaving the tower is more a function of the amount of evaporation that takes place than the DB temperature difference between air and water. Theoretically, WB, entering air temperature is the lowest temperature of the cold water outlet of the cooling tower can be reduced. If diis happened, it would mean that the atmosphere leaving die tower will be saturated. In practice, it is not economically feasible for the construction of the tower, which is always cool water WB temperature entering the atmosphere. Therefore, in most cases, the die temperature of the cold water leaving the tower will be in the range of 7 to 10 F (4 to 6C) above, the WB temperature of the incoming air. Therefore, the atmosphere leaving the tower will also be less than saturated.
Increase the number of evaporation occurring in the tower, thereby reducing approach, the quantity of water surface is exposed to the atmosphere should be maximized. The surface of hot water are die atmosphere increases the evaporation rate is also increasing. The same is true if the length of time diat water is exposed to the atmosphere increases. These features are implemented in the cooling tower designs to make them more effective and in large applications, dian the same size, with air-cooled condensers...
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