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Anonymous Poster

Evaporative Coolers for Swimming Pools

08/20/2010 3:07 PM

we have 750 cubic meters swimming pool, during summer our water ranging 30-40 deg. celcius which is not comfortable for the swimmer, we have 2 filtration pump running 24/7, six nos. of supply lines, water pressure of 1 bar @ 2 inches pipe, flow rate of 6 liters per minute. How does an evaporative coolers as sprinklers exposed to normal atmosphere and to be erected 2 meters height whose diameter is 2 inches with 1 meter length. I want to reduce my water temperature to 25 degrees celcius to make it comfortable for the swimmer. Please give me an alternative solutions without using water chiller. I'm very much interested for evaporative coolers using pumps rather than fans.

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#1

Re: evaporative coolers

08/20/2010 3:11 PM

Is the pool above ground?

If so, keeping the water level below ground level should help a lot.

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#2

Re: Evaporative Coolers for Swimming Pools

08/20/2010 9:49 PM

A spray pond ought to work for this. Off to the side of the pool, make a basin with with an array of nozzles spraying upward and falling back into the basin. Pump from the pool to this piping array, and let the water gravity drain back to the pool.

The pool will need more than the previous make-up water, which may require adjustment of the chlorination or other treatment system.

Offhand I don't know how to size this, but maybe it's a start.

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#3

Re: Evaporative Coolers for Swimming Pools

08/21/2010 3:30 PM

Do not work with them, but know : the output of an evaporative cooler depends on ambient air relative humidity (no latent heat can be get at 100 % RH).

And I believe a more or less effective evaporative cooling is impossible without fans - one needs a water-to-air heat rejection point.

Probably, in the end, you would not do without a refrigeration cooler (750 tons of water is too much to achieve a not too lenghthy cooling down from 40C to 25 C - by an EC ).

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#4

Re: Evaporative Coolers for Swimming Pools

08/21/2010 3:57 PM

What's your relative humidity? Evaporative cooling won't work on the Gulf Coast of Mexico.

You'll have to evaporate one liter of water for every 30 - 35 liters water cooled. This comes from 20% r. h. in the desert and the sensible heat and latent heat of evaporation of water.

You can get an idea of the heat duty from the makeup water rate.

If the heat duty requires evaporating 20 liters/hour then 10 liters/min of water must be pumped through the system.

Unless you know of some other way to keep the air moving, you'll need a fan. Pre humidified air won't work. About 5 orders of magnitude more air must be exchanged than liquid water on a volume basis.

Pool chemicals will be stripped out at a higher rate using the method posted above but the only alternative is a cooling tower.

If you simply add cool water you'll either have to dump the entire pool volume several times a week or you'll never cool it down.

Bret Cahill

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#5
In reply to #4

Re: Evaporative Coolers for Swimming Pools

08/22/2010 2:27 PM

Humid air at those temperatures is 4% lighter than dry air. It'll also be 15 C cooler and therefore 1% heavier overall. Natural convection won't work.

You need a 1 m^3/sec air flow rate, a $20 window fan.

Pool chemicals are expensive and 1000 m of 25mm sch 20 pvc tubing is only $300.

You already have a pump and a fan so you might as well make a cooling tower.

Just make sure you have a lot of parallel lines to keep the pressure drop and pumping costs down.

A 0.5 kW pump will pump 100 liters/min through 10 lines because the pressure drop is so low.

The only part of a cooling tower that may be a problem is making sure there are no dead spots. There's something in heat transfer handbooks about how to space and locate the pipes.

Bret Cahill

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#6

Re: Evaporative Coolers for Swimming Pools

08/23/2010 4:31 AM

25degC?

OK.

What's the wet-bulb temperature of the surrounding air? If it's ordinarily over 25degC, then evaporative cooling will only work if a fridge plant is installed as well.

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