Effective Thermal Design Of Cooling Towers (original) (raw)
Various misconceptions arise when it comes to the thermal design of cooling towers. Sometimes related parameters, such as range, approach, effectiveness, liquid-to-gas ratio ( L/G), wet-bulb temperature, cooling water temperature, relative humidity, number of transfer units (NTU) and other terms create a confusion for the designer in effectively sizing, selecting and evaluating a particular cooling tower. This leads to inadequate design.
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Applied Thermal Engineering, 2012
A thermodynamic model was developed and used to assess the sensitivity of thermal performance characteristics of a closed wet cooling tower to inlet air conditions. In the present study, three cases of different ambient conditions are considered: In the first case, the average mid-winter and mid-summer conditions as well as the extreme case of high temperature and relative humidity, in Athens (Greece) during summer are considered according to the Greek Regulation for Buildings Energy Performance. In the second case, the varied inlet air relative humidity while the inlet air dry bulb temperature remains constant were taken into account. In the last case, the effects on cooling tower thermal behaviour when the inlet air wet bulb temperature remains constant were examined. The proposed model is capable of predicting the variation of air thermodynamic properties, sprayed water and serpentine water temperature inside the closed wet cooling tower along its height. The reliability of simulations was tested against experimental data, which were obtained from literature. Thus, the proposed model could be used for the design of industrial and domestic applications of conventional air-conditioning systems as well as for sorption cooling systems with solid and liquid desiccants where closed wet cooling towers are used for precooling the liquid solutions.
Thermodynamic study of wet cooling tower performance
International Journal of Energy Research, 2006
An analytical model was developed to describe thermodynamically the water evaporation process inside a counter-flow wet cooling tower, where the air stream is in direct contact with the falling water, based on the implementation of the energy and mass balance between air and water stream describing thus, the rate of change of air temperature, humidity ratio, water temperature and evaporated water mass along tower height. The reliability of model predictions was ensured by comparisons made with pertinent experimental data, which were obtained from the literature. The paper elaborated the effect of atmospheric conditions, water mass flow rate and water inlet temperature on the variation of the thermodynamic properties of moist air inside the cooling tower and on its thermal performance characteristics. The analysis of the theoretical results revealed that the thermal performance of the cooling tower is sensitive to the degree of saturation of inlet air. Hence, the cooling capacity of the cooling tower increases with decreasing inlet air wet bulb temperature whereas the overall water temperature fall is curtailed with increasing water to air mass ratio. The change of inlet water temperature does not affect seriously the thermal behaviour of the cooling tower.
A Simplified Procedure for Calculating Cooling Tower Performance
Tower coefficient is commonly used to characterized the heat rejection capability of cooling tower. A simplified calculation procedure of tower coefficient is presented. The procedure is then applied to a popular cooling tower model, to illustrate the relationship between tower coefficient and water-air flow ratio. The data from a cooling tower site test are provided to verify the Merkel cooling tower theory, which is the basis of tower coefficient concept.
To simulate an industrial cooling tower and study its performance based on The cooling load Approach to wet bulb DESCRIPTION :
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