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Discussion Starter · #1 ·
I've been kicking around the idea for a long term project of a large plywood tank in the garage. There are a couple of things I've been thinking about: either a very long stream tank, or maybe a large african cichlid tank, but ignore that for now.

Here in NC, summer temperatures get hot, and my garage will spend long periods of time in the 90's. Some big honking 2hp chiller is going to be out of the question because I'm too cheap.

So here's my thought: It's a big tank and it's got a big sump. How about a second pump in the sump that puts water over basically a big waterfall. I'm imagining something like a rain gutter at the top with slits to spill water over a piece of epoxy coated plywood, maybe with lava rocks attached, to evaporate off water, cool it, and drop it into the tank.

Has something like this ever been done? Should I lay off the drugs?
 

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My only concern would be that I doubt evaporation will bring the temp down by the 10 to 15 degrees you would need. I would think 10 degrees max. Someone with more scientific knowledge might be able to provide better figures. Also with that much water evaporating from a large tank you'll have to figure out how to dehumidify your garage or possibly end up with mold issues.

Harry
 

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In the evaporative coolers used at industrial sites the water being evaporated is not the water being cooled. There needs to be two water systems so there can be a transfer of heat from one system to the other. The water being cooled is pumped through what is basically a large radiator. The water being evaporated runs down over the radiator to a collection tank where it is pumped back up to the top to repeat the process. Heat is transferred to water on the outside of the system leaving the water in the radiator cooler. If you could cool water by just allowing part of it to evaporate, a glass of water sitting outside would cool down as it begins to evaporate.

Also, heat always flows "downhill," that is, it always flows from an area of high heat to an area of low heat. If the water in the aquarium is at 90deg and the water in the cooling tank is at 90deg there will be no heat transfer. You would need something to make the water in the cooling tank cooler than the the water in the tank. Normal industrial evaporative coolers are cooling water that is well above ambient temperature so the water in the cooling tank is still cooler. The evaporative coolers that are on top of the house (swamp coolers) transfer heat from the air to the water leaving the air cooler.

You could possibly see a small decrease in temperature because the evaporating water will still take a small amount of heat with it but I would be surprised if it even drops one degree. Basically the only heat that it will take with it is the heat that was input from the environment to raise it the last little bit necessary to evaporate. You may even see your tank temperature rise more quickly as spreading it out gives greater surface area for heat to be transferred from the air to the water.
 

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Discussion Starter · #5 ·
In the evaporative coolers used at industrial sites the water being evaporated is not the water being cooled. There needs to be two water systems so there can be a transfer of heat from one system to the other. The water being cooled is pumped through what is basically a large radiator. The water being evaporated runs down over the radiator to a collection tank where it is pumped back up to the top to repeat the process. Heat is transferred to water on the outside of the system leaving the water in the radiator cooler. If you could cool water by just allowing part of it to evaporate, a glass of water sitting outside would cool down as it begins to evaporate.
When I sweat, it cools me down, why wouldn't evaporating water cool down water? I think a glass of water does get cooler just by evaporating, but I could be mistaken. I think it just doesn't evaporate very quickly, and hence doesn't cool very much.

Also, heat always flows "downhill," that is, it always flows from an area of high heat to an area of low heat.
AKA the first law of thermodynamics.

You could possibly see a small decrease in temperature because the evaporating water will still take a small amount of heat with it but I would be surprised if it even drops one degree. Basically the only heat that it will take with it is the heat that was input from the environment to raise it the last little bit necessary to evaporate. You may even see your tank temperature rise more quickly as spreading it out gives greater surface area for heat to be transferred from the air to the water.
I'm thinking that maybe the thing to do is some sort of experiment. Maybe pour a small amount of water over a smaller version of what I am thinking about and measure the temperature before and after.

If all else fails, I've got a garage fridge. ;)

As always, thanks for the time and input.
 

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When I sweat, it cools me down, why wouldn't evaporating water cool down water?
The sweat evaporating cools down your body not the other sweat. Again there is a transfer of heat.

I think a glass of water does get cooler just by evaporating, but I could be mistaken. I think it just doesn't evaporate very quickly, and hence doesn't cool very much.
The rate of evaporation would definitely have an effect. I could be totally wrong, it does happen much more than I care to admit but I really think that any temperature drop would be insignificant. If I run into one of the physics professors tomorrow I will get their input.

I was just thinking that a large scale evaporation would cool your tank, but not necessarily through the evaporation, but through the cool water being put back into the tank to keep the tank full. Maybe if you are evaporating enough water, between the cooling effect of the evaporation and the cooler water being added to the tank, you would achieve the necessary temperature reduction. I will definitely try to talk to one of the physics professors tomorrow to see what they say.
 

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Discussion Starter · #8 ·
The sweat evaporating cools down your body not the other sweat. Again there is a transfer of heat.



The rate of evaporation would definitely have an effect. I could be totally wrong, it does happen much more than I care to admit but I really think that any temperature drop would be insignificant. If I run into one of the physics professors tomorrow I will get their input.

I was just thinking that a large scale evaporation would cool your tank, but not necessarily through the evaporation, but through the cool water being put back into the tank to keep the tank full. Maybe if you are evaporating enough water, between the cooling effect of the evaporation and the cooler water being added to the tank, you would achieve the necessary temperature reduction. I will definitely try to talk to one of the physics professors tomorrow to see what they say.
Markopolo above says a fan cools his tank by 4°. That makes me optimistic.
 

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I'm not sure how well this would work. You'd have to rig up something pretty decent, but:

Think of ponds. Waterfalls and sprinkler pumps are used in ponds to aerate and cool the water. You could rig up a system where water is sprayed in the air(maybe inside a sealed box) and falls back into the sump to be pumped back to the tank. It wouldn't necessarily cool down the water unless the air around it was cooler. Making a system where water dripped down(or sprayed) in front of a fan. It would certainly cool things down. If you know a bit about wiring, you could hook up a temperature controller to the fan to cycle it on and off depending on the water temperature.

I would also suggest insulating the aquarium to shield it as much from the 90 garage as possible. If you do get it cool, you'll want to protect it.
 
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