27 November 2023

Cooling Tower Basics | Cooling Water Chemistry |

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Cooling Tower Basics

1.) Cooling Tower

  • Cooling tower is a heat exchanger.
  • It transfers heat from circulating water to the atmosphere.

2.) Type of Cooling Tower

1. Natural Draft Tower:-

In this Air flow depend on the surrounding Which establishes the difference in between the warmer air inside the                    tower and external atmosphere.

2. Mechanical Draft Towers:- Use Fans

There are two types :-

(i) Force Draft Cooling Tower

(ii) Induced Draft Cooling Tower:- This is again two types:-  I.) Cross Flow        II.) Counter Flow

3.) Cooling Tower Terminologies:-

1.) Dry Bulb:- Ambient air Temperature.

2.) Wet Bulb:- The dew point of the air, which is also the coldest temperature to which water can be cooled by passing it through air.

3.) Make up:- Water  added to circulating water system to replace water lost from system.

4.) Hold up:- Total quantity of water in a system including basin ,sump, pipe lines.

5.) Blow down:- The water continuously or intermittently purged from the system to remove sludge and keep dissolved solids at a tolerable concentration.

6.) Drift:-Water loss from the tower carried by the wind.  (0.1% to 0.2%)

7.) Cycle of concentration:-comparison of dissolved solid in the concentrated water and make up water.

          COC =    Concentration of  TDS in C.T. water /  Concentration of  TDS in make up water

8.) Circulation Rate:-The Rate  at which water circulates through the   process exchangers is known as recalculating rate.

9.) Retention time:- The time required for water to fall from the distribution header to cooling tower basin.

10.) Range (R):- Difference between the hot water  temperature returning to cooling tower and cold water temperature leaving the cooling tower.

11.) Evaporation Rate:- The rate of water is being evaporated to cool the circulating water.

               E.R =  0.0018 *C.R.*  Delta T

12.) Approach (A):- Difference between temperature of cold water leaving tower  and the wet bulb temperature.

Approach = C.T. O/L temp.-Wet bulb temp.

13.) Efficiency:- Cooling Tower cooling efficiency.

Efficiency % = (R) / (R  +  A)


4.) Problems in Cooling water system

The four major problem associated with cooling tower:-

  1. Corrosion
  2. Scaling
  3. Fouling
  4. Microbiological Growth

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