10 replies to this topic

[paraschemix]

Dear sir/madam,
We are in the process of calculating cooling tower duty. Our question is this.
Whether we have to consider cooling tower capacity same as that of cooling tower circulating pump capacity or we should omit the flow rates of SSF (side stream filter : CW pump --> SSF --> CT basin) and blowdown ?
 

[breizh]

Consider reading this document to support your query .

 

Breizh

[mansari]

The file attached by Breizh is an excellent document on thermal design of cooling tower and covers all the key elements related to cooling tower design, in detail.

 

To answer your question, Cooling tower capacity is the flow rate circulating through the tower. Whenever you determine L/G (an important parameter for tower performance calculations), L (water flow rate) is the flow passing through the tower packing and in contact with incoming air "G".

 

Sidestream filters normally draw 3-5% of the pump discharge (cold water) and return filtered water back to basin, bypassing the tower packing, therefore this flow remains in closed circulation and does not come into main cooling water heat and mass balance and its hydraulic loading "gpm/ft2" 

 

Tower capacity is defined on the based of process cooling requirements, converted into water flow at a given temperature difference (range) specified by the vendor of the cooling tower. Flow requirement for side stream filters is specified separately (based on maximum allowable suspended solids) and this flow is added to the pump capacities, over and above the main stream recirculation.

 

Blowdown is also a function of water chemistry and allowable cycles of concentration, not part of the tower recirculation. Tower capacity is the flow rate of water measured at  cooling water main supply or return pipe, to or from the process plant respectively

[Venkat Subramanian_32163]

 TOWER PERFORMANCE VER4.xlsm   807.65KB   461 downloadsThe attached xl file will help in estimating the cooling tower capability. There could be VBA incompatibility. If so this can be rectified and shared again.

[mansari]

Excellent worksheet Mr. Subramnian.

[paraschemix]

Thank you Mr.Breizh, Mr.Mansari and Mr.Venkat Subramanian. It will help me a lot in understanding of Cooling tower.

[paraschemix]

Dear sirs,

I am working out on cooling tower basin calculation. I understand that the basin dimensions are based on the number of cells in CT, its dimension and how it is aligned. 

Now,

1. I am in searching for preliminary cooling tower basin volume and dimension.

2. Also for designing pump pits associated with it.

 

Any thumb rules..?

Procedures..?

[breizh]

http://www.cheresour...ng-tower-basin/

 

Consider this resource ( SPX .pdf) , you should find guidance.

 

Breizh 

Edited by breizh, 09 July 2013 - 12:52 AM.

[Venkat Subramanian_32163]

Cooling Tower Design Norms Typical:

Water loading = 5000 - 13000 kg/h m2

Air loading = 6500 - 9000 kg/h m2

L/G ratio = 0,75 - 1,5

Approach = 3 - 5 °C

Tower operating = 80% - 120% of the design

Fan pressure drop < 5 cm

Fan blades pitch =  3° (Summer +3°, Winter - 3°)

Air velocity = 1,5 - 2,0 m/s (1,2 - 1,8 natural-draft)

Design WBT = avg. June-September (<5% exceeded)

Minimum contact = 4900 - 7300 kg/(hr)(m2 ground area)

Nd (KaV/L) = 0,5 - 2,5

Drift losses

old type = < 0,2 % circulating rate

new = < 0,02 % circulating rate

Air/water contact

splash fill = 2 - 3 m2 surface per m3 fill

film = >60 m2 surface per m3 fill 

lCooling Tower Base Area required: 1Million Calories Heat Load requires 3.0-3.5m2 

[Venkat Subramanian_32163]

Procedure for CT acceptance: ATC 105 specified by CTI.

Typically evaluates nd=number of diffusion units= KaV/L.

[slmn]

thanks mr venkat

please upload the full description of the file if you have