Liquefying air

Nov 2013
Hi there.

I am interested in a process whereby you can liquefy relatively large quantities of air quickly. I'm not talking about compressing the air and cooling it (joules-Thompson) but rather, are you able to use a liquid helium refrigeration cycle and pass the air across a membrane or similar heat exchanger and get liquid/solid air on the other side?
The makeup of the air is not important, as long as its density is significantly higher than that of normal gaseous air. One problem I'm facing is that you may get icing on the heat exchanger and not be able to extract the liquid/solid air easily.

Any thoughts? the only reason I'm avoiding the compression/cooling approach is because I want a compact and relatively low energy consuming process, on top of this I need high quantities of the liquid air on demand.

Also if this system were just passively sucking air from the atmosphere, would the vacuum caused by the loss of air in front of the heat exchanger be enough to suck more air in, or would it need a pumping system?