Bleed off from Cooling tower

[sridhar1312]

Is there any formula to ascertain the bleed off recommended for cooling towers to ensure concentration build up in the cooling water system.We find many of the cooling towers does not have the provision for bleed off thereby the refrigeration system operates almost same condensing temperature as the Air cooled condition.
What is optimum quality of water recommended for the Cooling tower.

 

[BM4BRANES]

Uh oh, sounds like the immediate problem is scale build up. Installing a bleed valve now will not undo years of differed maintenance.

After you have resolved the scale(heat transfer) problem, or installed a new tower, a bleed valve needs to be installed. Once you establish the Cycles of Concentration, you might try this: "Bleed rate" = "evap rate"(1.8gal/hr/to) / "cycles of concentration". good luck.

 

[DRWeig]

Or, once you've installed the bleed valve as BM4BRANES suggests, put in a conductivity transmitter and controller. Find the optimum setting by consulting with whoever sells treatment chemicals in your area (but watch out for the sales pitch).

Good on ya,

Goober Dave

 

[RossABQ]

Most controllers are set for 1,000 - 1,200 micromhos conductivity, depending on the water chemistry and the amounts/types of minerals. I agree tho, water chemistry isn't the only problem here. It sounds like the air is bypassing around the fill, or air flow is inadequate.

 

[atlas06]

try looking into the dolphin water treatment system if no one wants to deal with chemical treatment.

incidently, I have read case studies and all on the Dolphin water treatment system and it appears to sell good. Even ASHRAE green tips list it as an energy and water saving system.

Question, does anyone out there has good experience with it? sorry sridhar if this is a highjack of your post, but I think it is relevant to your post.

 

[sridhar1312]

Attention: atlas06

Haven't come across dolphin system can you send link please

 

[atlas06]

http://www.clearwater-dolphin.com/market_research.htm

Yiu ought to develop the instinct to google out things.
Smile -

 

[RossABQ]

Atlas, ought to search on this forum for several threads about the Dolphin system! ;-) NO positive remarks, I can assure you! The people who are "accepting" it don't have to live with its failings.

 

[cjw81]

My advice, you should get a professional in to make an analysis of your system. you should get only a licensed guy to perform the work. They should have a pesticide applicators license.it does sound like you have multiple problems with the system. Do not take the possibility of legionella lightly.

 

[imok2]

Chemical savings are directly proportional to water savings. For a 10,000 gpm open recirculating system with a 10o D T.
Increasing from 3 to 5 cycles gives 85% of the water and chemical savings you would receive if the cycles were increased from 2 to 10.

As cycles increase, so does the fouling potential in the system. Suspended solids and contaminants also increase with the increased cycles of concentration. It is usually best to limit cycles at or below 5. Further increase does not result in significant makeup water and treatment chemical savings and may not warrant the possibility of deposit formation and system fouling.

Remember, only when water savings are of paramount importance should cycles be allowed to approach theoretical limits. Other safe and effective levels are the best.

 

[mauricestoker]

Atlas,

I've had a few physical water treatment salesman make their pitch. Pretty much the NIMBY repsonse, Not In My Bundle-Your's? I've spoken with a lot of plant operators, when we get to details, the answer has been that the water chemistry is not suitable.

 

[MFranklin]

3 gallons of water at minute for every 100 tons of capacity.
This is in addition to make up for carry over. Which is also 3gpm/100t. A rule of thumb from the ammonia refrigeration trade.

 

[marcoh]

All depends on the quality of the makeup water and how much dust is taken in. A well designed system with good quality water should achieve 5 or 6 cycles of concentration. You should talk to a local water treatment specialist who should know local water quality.

Of course your cooling towers need to be well maintained, have clean fill, clean basins, float valves that don't leak, side stream filtration systems etc all of which will affect performance.