This is a very old article but its always interesting when it pop's up again. Archive: https://archive.today/CgdbI From the post: >>I determined that there was no good tutorial on how the average person can liquefy nitrogen or air. A few references to cryocoolers, which use an internal helium Stirling engine to create a cold head exist, and I even saw one person use this as a means to liquefy nitrogen, allowing the gas to condenses as it passes over the head. This method is cheating because it relies on a self-contained refrigeration unit. I wanted to do this using regenerative cooling just like Carl Linde back in 1895.