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HWT : This is hot water temperature. This is the temperature of water going in to cooling tower.

CWT : This is cold water temperature. This is the temperature of water coming out of cooling tower.

WBT : This is wet bulb temperature of atmospheric air.

Approach : This is difference between CWT and WBT.

Range : This is difference between HWT and CWT.

L/G ratio : This is liquid to gas ratio, in cooling tower liquid is water and gas is air.

Evaporation Loss : During water cooling process of cooling tower some part of water get evaporate. This is called as evaporation loss, approximately it can be calculated as RANGE in deg C/6.11=evaporation loss in % of circulating water.

Drift Loss : This is purely a mechanical loss, some water droplets are get away through cooling tower fan and fall on cooling tower surrounding. This loss is called as drift loss, normally its value to be taken 0.005% of circulating water. In case of sea water cooling tower this loss can be calculated, designed and tested very accurately, since sea water can cause damages to surroundings.

Blow Down : During evaporation process, pure water gets evaporated leaving behind burden of total dissolved solids (TDS). This increased concentration of TDS gets accumulated at bottom of basin. To keep balance of TDS in circulating water it is required to take out some portion of water from basin bottom timely, called as blowdown. Approximate level of blow down can be calculated by following formula,
C=(E+D+B) / (D+B)
where E: Evaporation Loss, D: Drift Loss, B: Blow down, C: Cycles of concentration.

Performance curves are prepared based on design condition of cooling tower, same will be submitted to client by cooling tower manufacture. These curves are made for +/_ 10 % water loading and +/- 20 % heat loading, compare to design one. These curves are helpful to cooling tower users in order to maintain track record of cooling tower Performance.

Types Of Fills

There are basically two types of fills, Film fill and splash fill. Film fill are more effective compare to splash one, but are more sensitive to choking & clogging. Hence proper selection of fill for particular operation is very much important for better cooling performance.

Some of the film fill are : Cross Flutter (C-10-12, C-10-19, C-10-27), Straight Fluter, Straight Flutter with holes etc.

Some of the splash fill are : Optigrid fill, PVC V bar fill, Concrete bars, Timber laths, TURBO Splash PAC etc.

Recirculation

Cooling tower is designed for inlet air wet bulb temperature. This inlet air wet bulb temperature will be at higher level compared to atmospheric wet bulb temperature, this happens because of recirculation. Fumes coming out of cooling tower get partially recirculated through cooling tower air inlet causing higher value of inlet wet bulb temperature. Recirculation depends on type of tower, size of tower, its location, wind direction and exit air velocity. Recirculation needs to be properly calculated and considered during tower designing.

Cooling tower fan selection.

Cooling tower fan will be selected based on air volume requirement to cool the water and static pressure across cooling tower.