Cooling tower units 1

[kunal2603]

We got two cooling towers with same capacity in the plant. Initial plan was to operate them independently but these towers have come with equalizers and flume lines.
Is it efficient to operate the towers independently or together as one unit? There is no float v/v and make up water connection for one tower. I can fabricate and order floating v/v from Marley though. Your help will be appreciated.

Kunal

 

[katmar]

There are advantages of having them operate together as one tower. You have already pointed out the single level controller needed - others off the top of my head are single water treatment plant, better ability to handle short peak loads and simplified piping. In winter you may also get away with running only one fan.

In some instances you have to run your towers separately - especially if you have significantly different temperature rises, or if you have potential contamination.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[kunal2603]

Katmar,

There are no diffrent temperature rises here. Maximum in summer will be 95 deg F. If we run them as one unit, we have to shutdown both the units for maintenance which leave me without cooling water for the plant. Preventive maintenance of this tower during annual s/d will keep us away from unschedule tower maintenance?

 

[dcasto]

Outside temperature isn't the controlling factor, it air dew poit (wet bulb) that matter. In my opinion, it would be better to have them connected more for the ability to also control your cooling at the end devices by better balancing loads there.

 

[kunal2603]

Dcasto, thanks for your suggestion.Sorry for the confusion. The max inlet water temperature to the cooling water is 95deg F. Entering Wet bulb Temp is 80 deg F . Conditions are to cool 97 deg F water to 86 deg F .

Can anybody tell me how do we calculate wind load? My vendor has given the value (50psf) though.

 

[katmar]

In response to your comment about maintenance - a cooling tower very rarely breaks down. The most likely items to require breakdown maintenance are the mechanical items like the pumps and fans. Generally the pumps would have installed or easily installable spares, so a breakdown here is unlikely to be a major problem. If fans are inspected and overhauled during the annual shutdown it would be unusual for them to give problems during the year.

By temperature rise I meant the difference between the supplied and returning water. For example, fermenters can require a set temperature close to your cooling water temperature, but the driving force is very small. In this case the cooling water may heat up by as little as 2 or 3 degrees C on its way through the cooler and back to the tower. On the other hand, a condenser on a distillation unit may allow the water to heat up by as much as 10 degrees C. Mixing these two returning stream would not be efficient.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[kunal2603]

Katmar, Thanks for the valuable post

 

[krb]

Can you provide info on how the pumps are connected and how the fans are controlled? Also, how much does the water flow vary during the year as there is a minimum and maximum flow rate for each tower.