Air Liquefaction

At a very general level, if the entire liquefaction were done using a Carnot cycle, the efficiency would be quite low, perhaps 20-25% for air. However, the precooling can be done by one of several reversible processes, all of which have high efficiencies perhaps as high as 80-85%, followed by a small Carnot cycle for the actual liquefaction. Thus, just as a theoretical example,you might have 90% of the work done at 85% efficiency and 10% done at 25% efficiency. The total efficiency would then be

(0.90)(0.85) + (0.10)().25) = 0.79 or 79% efficiency overall.

You should consult a good cryogenic engineering reference for actual numbers (the ones used in the example were just made up) and to see how the various processes such as Stirling fit together.

Thou art a scholar; speak to it, Horatio. - Hamlet

Hi guest

I find this a very good question, I don't know the answer, I only make general assumptions. I would like to see many responses to this. But I am afraid (anonymous, not from the States they easily threat you as a scavenger here. Even if they are considered as multicultural and broad minded)

Most likely it is often more expensive to need two machines in on process even when the gains are considerable. The theoretical gain versus the practical gain is often very poor.
You always have to pay for the learning curve. The expenses are growing exponentially with the depth of it, so if you install a pre-process for the easiest gained merits. In general you gain not that much.

In this case it is less of a topic, space constraints, weight constrains, people skills/ history, target group, are often an important factor.

There is often the fragile link between two processes. To manage a double set of parameters.

In the past energy was cheap and is was not worth while installing a secondary process.

People start often with the easiest process, gain experience, and don't bother for alternatives, because they have experience with the first process. Unless they are forced too.

The cost of being operative. Double set spare parts, multiple skills, require assistants of two suppliers.

The American standard is often when you not gain money in the second year the product will be disposed off. Why bother to build a more difficult process. Even Einstein said it "out of the clutter find simplicity"