As the name implies, thermoacoustics studies the interplay between heat and sound. My first exposure to the topic was Sondhauss oscillations, where hot glass starts “singing” sine waves.
Standard refrigeration works by vapour compression… What is a sound wave, if not a fluctuating pressure wave? To shorten a long ramble into one, potentially confusing, statement; If you can get a sound wave bouncing back and forth inside a tube (filled with helium at 17 bar), with nodes in the waveform interfering, and heat exchangers placed strategically at high and low pressure nodes, you can achieve single stage cryogenic cooling, with only one moving part, aside from the “working fluid”. I know that’s going to be hard to read, but I’m lazy, trying to be concise, and there are better resources for understanding how it works than something I haven’t typed yet anyway, including the sales brochure I plan on linking to.
The world leaders in this tech are a company called “QDrive”, along with Los Alamos labs. I was looking into thermoacoustic cryocoolers well over a decade ago for liquifying oxygen, and decided it wasn’t economically viable for me at that point, but I’ve kept an eye on the company since. They and their parent companies keep being bought up by bigger and bigger fish, and they are currently in the belly of the military contractor RIX Industries.
So yeah, who’s interested in efficient, single stage cryogenic cooling?