Open Cooling Towers are used to dissipate heat from water cooled refrigeration, air-conditioning, and industrial process system. Open Cooling Towers can economically cool water to within 5℉ to 10℉ of the ambient wet bulb temperature or about 35℉ lower than Air Cooled systems of reasonable size.
The thermal performance of open Cooling Tower is defined by Range and Approach:
- Range: The temperature difference between the water entering and leaving the Cooling Tower.
- Approach: The temperature difference between the leaving water temperature and the entering air wet bulb temperature in the Cooling Tower. The approach is a function of Cooling Tower capability, therefore a larger Cooling Tower will produce a closer approach (colder leaving water)for a given heat load, flow rate, and entering air condition.
The thermal performance of an open Cooling Tower is affected by the entering air wet bulb temperature and relative humidity. The evaporation rate at typical design conditions is approximately 1% of the water flow for each 12.6℉ of water temperature range. In addition to water loss from evaporation, losses also occur because of liquid carryover into the discharge airstream (drift) and from blow down (to maintain acceptable water quality).
There are two main configurations of factory assembled open Cooling Towers:
- Cross Flow: The water flows vertically down the fill as air flows horizontally across.
- Counter Flow: The water flows vertically down the fill as air flows vertically up.
There are two types Fan System in Open Cooling Tower:
- Induced Draft: The axial fans of induced draft equipment are mounted in the top deck of the unit, minimizing the impact of fan noise on nearby neighbors and providing maximum protection from fan icing with unites operating in sub-freezing conditions. The use of corrosion resistant materials ensures long life and minimizes maintenance requirements for the air handling components.
- Force Draft: The fans are located on the air inlet face at the base of forced draft towers, facilitating easy access for routine maintenance and service. Additionally, location of these components in the dry entering air stream extends component life by isolating them from the saturated discharge air.
