Evaporative coolers

[ksteiny]

Posted this question in the aquaculture forum and didn't get any response so thought I would give it a try here. Does any one have any experience with these cooling there fish rooms? I live in the midwest and we have very hot and humid conditions in the summer. I want to cool a large out building/fishroom and I don't know if this type of system will work or be efficient in high humidity climates. They seem to be popular in the greenhouse industry. Any suggestions or personal experiences would be appreciated.
Thanks,
Kevin

 

[DJ88©]

Kevin,

I think this is more of an advanced type topic. If you don't get any responses to this here let me or another mod know and we will find a proper home for it.

[moved]

 

[Weatherman]

Evaporative coolers are not the best choice for humid climates. At best, they can only lower the temperature of the air down to the wet-bulb temperature (which is a few degrees higher than the dewpoint temperature). At the same time they lower the temperature, they increase the humidity. So, on a typical summer day in Missouri, an evaporative cooler might lower the temperature to around 80, but increase the humidity to near 100%.

Greenhouse plants love it, but 80 degree air with 100% humidity would not be good for a fish room.


My only personal experience with evaporative coolers was in Californiaââ"šÂ¬Ã¢"žÂ¢s Central Valley. The college I went to used them to cool the classrooms. They turn 105 degree air with 55 dewpoint into 75 degree air with 70 degree dewpoint really well. Unfortunately, I never considered 75 over 70 to be comfortable indoor conditions.

 

[ksteiny]

Thanks for the input weatherman.

 

[Nathan]

My vote goes for a standard Air Conditioner. Trust me, it works and costs less than an expensive "chiller" AND you get the advantage of a cool room!

-Nathan

 

[castorpollux]

ditto with Nathan, the swamp coolers work wonders in colorado where im from but in kansas city where my family lives it would make life a living hell...

 

[Fredfish]

I remember some discussions years ago about evaproative cooling towers and if they are constructed properly, they can work.

However, I would think that a better approach would be to set up an in ground cooling (geothermal) system using pvc piping. There are several good discussions here on RC if you can find them. It takes quite a bit of effort to set one up because you have to bury a long run of larger diameter (4") piping deeper in the ground (deep enough to get cooling effects). They are, however, very effective.

Fred

 

[ksteiny]

I have seen them working in a few local green houses. They say that they can keep the temp. in the low 80's but condesation and humidity are definatley a factor. Especialy with large open tanks of water. I like the idea of being able to keep the whole room cool, which is why I was exploring the evap. coolers since they are much cheaper to run than standard a/c. I think that what weatherman and others have said though about having the hummidity at close to 100% would make it very uncomfortable to spend any amout of time in there even if the temps were in the upper 70's. And it could definately be a problem with mold and mildew as well. I have also cosidered using a geothermal type system running off of well water. Should be much easier than burying pipe. Also you can buy titanium heat exchangers that are much more eficient than pvc(also more expensive).
Kevin

 

[Fredfish]

Yup, lots of options. There was a web site called titaniumjoe.com that sold recycled tytanium at reasonable prices. I wonder how much you could reduce your run if you burried titanium.

Fred

 

[H20ENG]

The ground would heat up locally around the tubing with the short runs of ti. It would depend on how much cooling you needed though. A whole greenhouse vs just a tank.
This is why many commercial Geo loops use the Pex tubing. You could use copper, but the ground can only absorb so much. The longer runs spread the heat out enough to make it viable. The PEX heat transfer is nowhere near that of copper, but works fine with such long runs.

 

[jrc541]

Kevin,
This is actually a complex design problem for an HVAC engineer because the solution lies in the correct estimation of evaporation which varies according to several factors in the physical environment. To get it right you'll need to spend a bit of money to hire a pro that is fanilar with ASHRAE guidleines and you'll end up with an expensive commercial type system.
A standard AC won't work because they typically haved a fixed sensible heat ratio of .75. This will result in overcooling, equipment cycling and poor dehumidification.
Explanation:
Total heat = sensible heat + latent heat
Simplifying, sensible is the dry heat, latent is the moist heat.
Sensible heat ratio = sensible / total
Not sure what a fish room SHR is but I bet it's more like 0.5
A coworker is working on something simlar using a Desert Air unit. Material cost in our case = $10k for 36,000 BTUH
These links might help - pools are decent comparison

[url]http://www.desert-aire.com/pdf/AN/an10.pdf[/URL]
I'd be interested in hearing more from the public aquarium engineer.
John

 

[Fredfish]

Hmm, hadn't considered heat dissipation in the ground. What exactly is pex tubing?

Fred

 

[H20ENG]

Cross linked polyethylene. Thick walled , tough stuff.

I know that when designing for big geothermal systems, they test the soils' makeup to see what the thermal conductivity is to the earth. If its not ideal, they can add certain clays and whatnot to help it transfer the heat. They also can predict if the ground will simply heat up and stop providing enough heat transfer. Not sure of all the formulas....

Seems like I read to use about 400-600' of tubing per ton of cooling. Remember though that this is for refrigerant based systems, where the heat differential (and therefore heat flow through the tubing to the ground) is much greater. We would need more tubing to get enough cooling in our relatively low differential delta T setups.

 

[ksteiny]

One of my many ideas (I am full of lots of things) is to either run tank water down to a well through a titanium heat exchanger or more likely to run well water up to my systems through a heat exchanger or series of heat exchangers then back to the well. Basically a closed loop. I hadn't really considered running piping in the ground. I would think that the well idea would be much more efficient and easier to set up. Does anyone see any draw backs compared to an in ground system. I have the ability to do it either way. Obviously if my well went dry I would be screwed. I think I could adequately cool my tanks with this sort of system, but that still leaves my building to cool. The building size is aprox. 2800sqft. Work shop and garage area will be seperate from tank area. Seems at this point that maybe just standard a/c and maybe the way to gokeeping the tanks on a seperate system and controling the a/c for comfort as needed.?? Could outside air be drawn over a heat exchanger or radiater type system to acheive any signifigant cooling. Like maybe before my well water closed loop enters the tanks or even a seperate loop??? I appreciate everyones input. Also do you have any links on the pex tubing?
Kevin

 

[H20ENG]

The well water would be very efficient. You dont want your tank water in a loop that could be shut down to stop the cooling cycle, it'll go sour. I would put a copper coil down in the well running to a Ti coil in the sump or other exchanger. Run freshwater in this loop and control its pump by your cooling thermostat.
Another thing to watch for with a well system is how slow the aquifer is. Probably fine unless you were cooling a huge commercial building.

 

[ksteiny]

I was thinking a pump in the well straight to my exchanger in the tank or tanks and then just dumping the water back into the well. Don't see a need to have a coil in the well and run it closed, maybe I should say it is more of an open loop. Do you see any disadvantage to this over the coil in the well? What about the radiator idea for cooling the building??

 

[H20ENG]

The one disadvantage I see is electrical consumption. Your well pump is probably at least 3/4HP, where a small close loop pump will only run 100 watts or so. But it would work...

 

[ssgatbliss]

Re: Evaporative coolers

<a href=showthread.php?s=&postid=6840338#post6840338 target=_blank>Originally posted</a> by ksteiny
Posted this question in the aquaculture forum and didn't get any response so thought I would give it a try here. Does any one have any experience with these cooling there fish rooms? I live in the midwest and we have very hot and humid conditions in the summer. I want to cool a large out building/fishroom and I don't know if this type of system will work or be efficient in high humidity climates. They seem to be popular in the greenhouse industry. Any suggestions or personal experiences would be appreciated.
Thanks,
Kevin

Short answer is the don't work in medium humidity let alone high read on for longer answer!

***************************************

Recently moved from El Paso, Texas to Colorado Springs, CO and most homes in the south west use swamp coolers as did mine. The problem with swamp coolers is it is very hard to control the temperature and they DO NOT WORK WELL IN MEDIUM or HIGH HUMIDITY!. In low humidity areas with high temps (like El Paso used to be) they work well but in July/August when the humidty gets above 40-50% they stop working. I ended up putting window units in the bedroom and my office because we didn't want to spend the money on central AC since we were moving.

Also swamp coolers add a ton of humidity to the house which is great for evaporation from the fish tank but devastating on anything wood. The doors stop closing properly and pictures that aren't framed well will simply fall off the frame or bulge up under the glass. And maintenance on the damn things is a pain also. El Paso had very hard water and every two months the evap pads looked like icebergs from the hard water deposits. Good swamp coolers cost more than most very large window units and that's without the pads. The "good" pads (Aerocool/Mastercool) run about $100 a pad and my two coolers needed two pads a piece. They say they have a five year warranty but that's only if you have soft water in your area. I had to replace mine every year andI had special pumps installed to exchange the water in the sumps every 4 hours which illegal in many areas due to the wasted water. The waste water can't be used for anything, I learned the hard way and killed a large section of my lawn and a tree by trying to use it to assist watering the lawn (had to replace the soil to correctthe problem, not fun).


To give you an idea I had two Mastercool units running 24/7 in July/August on 2200 square feet of home and the temp couldn't get below 85 in the house and that's with temps of 100 outside and about 60 percent humidity which used to be unheard of but is now becoming common place with all the swimming pools and golf courses going in. If you shut the coolers off for even a short time the temps skyrocket and don't come down until you get a break inthe weather. Most decent manufaturers sites or installers will tell you that swamp coolers are only meant to drop the temps 10-15 degrees F. Rainstorms render them useless.

Hope that helps, I'll never use them again.

 

[H20ENG]

ssgatbliss
Thanks for the first hand knowledge.
I know that there are now dual stage (direct / indirect) evaporative coolers which help with the indoor humidity, at the higher expense of more moving parts and maintenance.
ANY evaporative cooling process is at the mercy of the outdoor wetbulb temperature, which makes them a good choise only in certain climates.