My son's science project involves liquifying air. I found the Linde process which is the way it was done first. We are trying and not getting very far so I am looking for advice.
I have an air compressor good to 150psi. We are slowly ramping up the pressure in the system. We are currently testing at 80psi. We pressurize 20 feet of copper tube bent in a coil running through an ice bath. The tube exits and goes into the bottom of a thermos. The end of the tube is capped, and we allow a small leak so that pressure drops from 80psi to 1atm.
We insulated the few inches between the ice bath and the thermos. We do not yet have a double walled tube, but we taped the thermos so all the air coming out is exiting through the insulation.
When we run, the thermos drops from room temperature (about 68F in the basement) to our best of 45F. I'm quoting in Fahrenheit right now because the boys are very obnoxious about not wanting to use a temperature system they aren't comfortable with, and I just haven't been able to convince them that they are being unreasonable.
The point is, we are not even achieving the temperature of the ice bath. Incidentally, as measured with my multimeter, the ice bath is always 3C. I'm curious about that too, but that will be a separate question. Needless to say, we are not achieving any refrigeration.
The next step we will increase the leak so that the flow through the system is much higher. And we will start trying to use a Peltier cooler so we can have an intermediate stage that is 20C or so cooler than the ice bath.
Obviously we can up the pressure, but I would think we should see something more than we are getting. Any suggestions? Should I take a picture of our setup?
