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:-
- Corrosion
- Scaling
- Fouling
- Microbiological Growth
