Hot Air - Does It Matter?

[TwoTankAmin]

I was just over on Planetcatfish reading a thread dealing with tank temps and controlling heat. It was suggest that in warm weather filters and powerheads etc. all act to warm the water. The OP was concerned about low O in his tank due to higher temp water. He a;so observed that at times the ambient temperature where the tank was could hit 90F. A number of posters suggested using air stones to help oxygenate the water and to avoid or minimize the issue of equipment generated heat in a tank.
 
However, I saw an apparent issue with this advice. The temperature of the air going into a tank should be slightly above the ambient temperature. The slightly above (how ever much or little it is) would be contributed by the heat generated from the mechanical parts of the pump itself. But what I thought this all boiled down to was that bubbling 90f+ air through water of a lower temperature would act to raise that water temp. by some amount.
 
So my question here is how much heat (or cooling for that matter) can aeration contribute to the overall tank temperature. Is it a meaningful contribution towards heating or cooling or is it basically so minimal that it doesn't matter. Would it matter if one doubled the amount of aeration?

 

[Chad]

Living in Arizona I deal with heat issues a lot. My understanding of this is that just like sweating cools the human body via evaporation air over the surface of the water will cause evaporation and usually a a couple degrees of cooling through the energy lost by the process of evaporation. I'm not sure what benefit, if any, is derived by pumping air into the water itself. 

 

[TwoTankAmin]

Tcamos- the original issue was one of getting more oxygen into the water. There were suggestions of adding filters, adding a powerhead with a venturi etc. The poster then observed that a powerhead in a tank with a venturi would create heat in the water and at times the ambient temp there was 90F or a bit higher. The implication was that most ways to aerate the water would also be adding heat to the water. Then the comment was made that using air pumps and air stones would help with both the oxygen issues and the heat issue.
 
So my question had nothing to do with evapoartion but with the fact that if one is using an air pump and airstone and the air going to the air pump was at 90F, would those air buttble coming out of the air stone not be 90 F? I further wonder since and airpump motor makes heat inside the pump,would that also not act to heat the air going through? Ultimately, the question I am asking is: If one pumps air bubbles of 90F+ air into a tank which is a lower temp than that, wont those bubbles act to raise the water temperature?
 
Now I know that the bubbles breaking the surface would move a bit of air over the surface, but then so would any equipment that roiled the surface thereby moving some air at the surface/water interface.
 
But perhaps it is easier to answer the question when one considers the reverse. Lets say I have a tank at 80F and I hook up my air system so it runs through a container filled with water and ice. I use a long enough airline so I get a bunch of coils in that bucket so the air temperature in the airline before it goes into the tank is now 40 F. What effect would sending 40F air bubbles through the water to the surface have on the temperature of the 80F tank water? Would the cold air bubbles drop the tank temp?
 
If I bubble very warm or very cold air through an airstone in a tank- will it affect the temperature of the water over time?

 

[Chad]

Ah, I thought they were trying to cool the tank.
 
Yes, I've done this before. I'm not sure of the physics involved but pumping cold air will lower water temp. Perhaps the bubbles work as a means of forced convection and transfer the heat out of the water. Not sure. However, because liquids aren't that great at heat transfer the air pumped in needs to be quite a bit cooler.
 
Heat from pumps works on conduction much like boiling water on the stovetop that much I do know.