Water cooling tower design

Additional detailed information is available from the Cooling Tower Institute, including ATF-105 Acceptance Test Procedure for Water-Cooling Towers, STD-101 CTI Grades of Redwood Lumber [31], STD-102 Structural Design Data [70], and TSC-302 Cooling Tower Wood Maintenance [16],... 

Water quality is important, not only from an environmental point of view but also in relation to the type of packing to be specified. Analysis of the circulating water is simple to obtain, but it is very seldom offered to the cooling tower designer. The quality, or lack of it, will determine the type of pack to be used, the selection of structural materials and whether the tower should be induced or forced draft, counterflow or crossflow. Water treatment, in the shape of chemicals to control pH and to act as counter-corrosion agents or as biocides, all has a bearing on tower selection. 

The design of water-cooling towers, and humidification, is covered in Volume 1, Chapter 13. The same basic principles will apply to the design of other direct-contact exchangers. 

For example, a cooling tower with water containing four times as much total dissolved solids as its makeup supply would be operating at four cycles of concentration. The cycles of concentration are determined by the cooling tower design, water characteristics, operating conditions and the type of treatment system employed (cooling tower water treatment is discussed in detail in Chapter 8). 

Our discussion up to now has concerned the cooling of hot process waters exclusively. However, we insisted back in Chapter 1 that a cooling tower is nothing more than a device that transfers heat from one mass to another. Therefore, gas coolers are governed by the same theory of operation and design principles as are water cooling towers. 

Design problems of water cooling towers and their use in various water cooling systems are discussed. 

A large capacity sea-water cooling tower is designed with a drift eliminator to drastically reduce the drift carry-over. The drift carry-over from the tower has in fact been reduced to only an order of 6 to 7 X 107 of the quantity of sea-water circulated for cooling, or is as low as 1/2000 or less as compared with 0.2% in the conventional fresh-water cooling tower. The present paper gives an outline of the service results of this cooling tower. 5 refs, cited. 

A Method for Designing Counterflow Water Cooling Towers Vojislav, A. 

In some cooling tower designs, the main hot water distribution pipe running the length of the tower and supplying other smaller (lateral) pipes. 

The final components used in the distribution of hot water through a cooling tower, designed to break up water into finely dispersed droplets. 

FIGURE 5.10 Diagrams of direct (evaporative) and indirect cooling towers designed to shed heat loads to air rather than surface waters. 

Develop the design equation for water-cooling towers and dehumidifiers using air. 

Equation (8-32) is the design equation for water-cooling towers. The integral corresponding to the number of transfer units, N/G, is evaluated numerically following the procedure illustrated in Chapter 5 for absorbers and strippers if the individual coefficients hL and ky are known. The equilibrium curve for cooling water with air at 1 atm is that shown in Figure 8.2. 

C Design of Water-Cooling Tower Using Film Mass-Transfer Coefficients... 

Design of Water-Cooling Tower. Recalculate Example 10.5-1, but calculate the minimum air rate and use 1.75 times the minimum air rate. 

In both these cases, the area ABCD should remain constant—actually it decreases about 2 percent for every 10°F (5.6°C) increase in hot-water temperature. The cooling tower designers take this into consideration in their initial design by applying a hot-water temperature correction to design calculations when the design hot-water temperature exceeds 110°F (43.5°C). See Fig. 3.21. 

This expression, known as the Lewis relation, when used to compare Equation 9.1b and Equation 9.2b, leads to the conclusion that the adiabatic saturation and wet-bulb temperatures are essentially identical. The Lewis relation has other important implications as well, as will become apparent in Illustration 9.4 dealing with the design of water-cooling towers. It is seen there that the underlying model equations can be enormously simplified by making use of the Lewis relation. 

In heat transfer applications, either the liquid stream or the gas stream can be cooled. The most common application, in which the liquid stream is cooled, is a water cooling tower. Although there is sensible heat transfer between the warmer water and the cooler air, in this device the warm water primarily is cooled by evaporation of some of the water into the air stream. Both the heat and mass are transferred in the same direction, from the water to the air stream. Exit air from the water cooling tower may be assumed to be saturated with water vapor. Kern reports tests showing the exit air is 95% to 99% saturated [2]. Exit air enthalpy can be obtained from a psychrometric table. The inlet air condition usually is defined by the dry-bulb and wet-bulb temperatures. For practical design purposes the inlet air is assumed to be saturated with water at the wet-bulb temperature, because the enthalpy of this air is sufficiently close to the theoretically accurate adiabatic saturation temperature. 

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