Joule-Thompson Cryocooler

Big thanks to @Exotic_Chem_Lab chem lab for sharing his experience to help make this project happen In this video I’m going to examine the performance of a homemade cryocooler using the joule-thompson effect. A joule-thompson type device was the first method that was used to liquify nitrogen on an industrial scale, but it was very inefficient. Using nitrogen at pressures of 200-300 bar, it would drop the temperature through a regenerative heat exchanger until it reached a low enough temperature that some of the nitrogen would condense to liquid when it expanded through a flow restriction. This process was very inefficient, usually less than 1% of input power went into actually cooling and condensing the nitrogen. I’m going to be taking a slightly different approach that’s a sort of half-way between a joule-thompson device and a vapor compression system. Instead of using air or pure nitrogen as a working fluid, I’m going to use a mixture of hydrocarbon gases (propane, ethylene, and methane), which have dramatically higher joule-thompson coefficients. Unlike a traditional joule-thompson system, this type operates in a closed-loop. Typical low side temperatures get down to -160C to -170C, which is enough to liquify air or pure nitrogen if it’s pressurized to 10-20 bar inside the cold end, which is trivial to do. Higher boiling gases will condense as the temperature of the cold head is reduced and cease to contribute to the joule-thompson cooling, but still make a major contribution to heat transfer when they evaporate in the regenerative heat exchanger. I built this system using the compressor and condenser coil from a 12K BTU portable AC unit (meaning the compressor pulls around 900W loaded). The oil separator is a temprite 900 series, and the heat exchanger consists of 30 ft (9m) of two 3/16“ tubes for the high pressure side and a single 5/8“ tube for the low pressure return line. I only reached -88C in this video, because a defective oil separator was causing oil to overflow into my heat exchanger and freeze at such low temperatures, resulting in clogs in the capillary tube. The heat exchanger also wasn’t properly insulated or pre-cooled in this video. With those changes, reaching -150 to -160C should be relatively easy with the correct gas composition. Music Used Kevin MacLeod - George Street Shuffle Kevin MacLeod - Groove Groove Kevin MacLeod - Lobby Time Local Forecast - Elevator