Tonight, I tried out an aquarium bubbler (perhaps actually called aerators
, I think).
The first thing I noticed is that the "whisper quiet" air pump is redonkulously loud
. It sounds like a jack hammer! I don't know how aquarium enthusiasts tolerate it. But, I was dumb about it. I just went to a pet shop and selected a pump that listed "quiet" as its primary design feature. I'll have to surf the aquarium web sites for a truly quiet air pump. (but only after I determine that bubbles actually help with cooling - I'll tolerate the noise while I experiment).
One thing I learned about the air pump: it is quieter under load. That is, it is loudest when running without any tubes plugged into it. Sort of like a car without a muffler. The air pump delivers air pressure in rapid bursts, and without something to dampen the output, it sounds very loud. But even after tubing up, the pump itself makes a lot
of mechanical noise.
The second issue I ran into is foaming. I mentioned in a previous post that, theoretically, little bubbles would cool better than big bubbles. This is because
- per unit air volume, little bubbles have more air/water boundary surface area than big bubbles do, which allows more heat energy to transfer from water to air
- little bubbles float to the top more slowly than big bubbles
One of the products is an air stone (a porous rock that you attach the air tube to which emits bubbles) which makes tiny bubbles (they said micro
bubbles -- no doubt someday to be obsoleted by nano
bubbles). I submerged that baby and turned on the pump. Yup, those bubbles were pretty small. And, immediately the bubbles formed a foam at the top of the oil. And the foam built up like the head on a mug of beer. I had to turn off the pump, lest the foam overflow the inner tank and spill into my outer (water) tank.
Not good. For one thing, a layer of foam would act as a thermal insulator, possibly negating the cooling benefit I sought by percolating air through the oil in the first place.
The other issue, of course, is foam spilling over and making a mess.
The Puget Systems people (Jon Bach @ http://www.pugetsystems.com/submerged.php
) reported that they had installed an aerator and occasionally it would start to foam up (they think
, because they'd sometimes find oil beside the tank). They didn't know why it sometimes did and sometimes didn't - but speculated it might be humidity. Personally, I have no idea what might be causing it. Jon
, do you have any more recent experiences to report on this? Also, your website mentions that you'll be revisiting this idea this spring -- how's that going?
Anyway, my bubble options seem to be
- Use bigger bubbles. They form less foam, perhaps because they pop more easily. But that means less cooling (theoretically).
- Turn the airflow down (again, less cooling)
- Don't fill the oil tank up so close to the top. Allow a couple inches of foam to build up - just don't let it spill over the sides of the tank.
- Research some kind of additive that makes the oil less foamy. I have no idea if such a thing exists. I still have to be mindful to keep the mixture nonconductive.
- Use bubbles in the water layer, not the oil. Water might not bubble up so badly.
- Don't use bubbles.
I hate to give up on the idea of bubbles for cooling, because it seems theoretically sound. And, if bubbles can be functional, that makes them extra cool to look at (pun intended).