Making Liquid Air
Most recent answer: 01/22/2014
- Dov Kruger (age 47)
Teaneck, NJ, USA
This is a really interesting project, and it sounds like you guys have put some real thought into it. Unfortunately, I don't think that a single-stage compressor cooler of the type you're using will be able to get cold enough.
Let's follow through on that adiabatic calculation you were doing. It has a lot of approximations and idealizations, but it's still a good starting point. You want to reduce the absolute temperature about a factor of 4 to get liquification at atmospheric pressure. If we treat the gas as ideal with a fixed gamma of γ=7/5, we end up with p proportional to T(γ/(1-γ)). That would require p of 128 atmospheres, way beyond what your compressor can do.
In principle you could do this with multiple stages of compression, with each stage taking a portion of the material from the previous stage and cooling it further. I suspect that's much too elaborate for a home project.
Still, the project sounds worth pursuing to see how cold you can get it. I'm not sure why your current set-up isn't getting the air colder than the ice bath. Your idea of playing around with different types of leaks sounds good.
Mike W.
(published on 01/22/2014)
Follow-Up #1: limits on cooling air
- Dov
Teaneck, NJ, USA
Here's a first thought. You mentioned flecks of ice. The latent heat for converting water vapor to ice is very high. You could be removing heat from the gas but instead of lowering the temperature much it's just causing bits of ice to freeze out. If it turns out that's what's happening, it's a pretty interesting result even if it's not what you were aiming for. Maybe this is a long shot, but if you could start with dehumidified air (from the airconditioner?) maybe you could at least see more noticeable cooling.
Mike W.
(published on 02/08/2014)