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Comment by kragen | Hacker News Reader

probably if you are trying to understand how this works it would be useful to read https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine

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This and the posted article mention a speaker or driver. No mention of how they deal with aging or fatique effects in e.g. a flexible ring connecting to the frame and holding the cone. Have done applications where a special "high cycles" acoustic driver had to be sourced.

i hadn't thought about that; it seems especially important given that they're talking about kilowatt power levels and macroscopic wavelengths, so a nice piezo probably won't cut it

how did you source the high cycles driver, what was it made of, and how much did it cost

I just found this[1] which mentions rubber vs. foam surrounds (suspensions), and butyl rubber with apparent good life. (That might have been the simple difference; the normal-looking speaker was already sourced; I came in to do embedded/DSP.) At kilowatt/constant power levels I'd imagine going as far as oil/magnetic suspension for high life; even o-rings under high cycles can fall apart.

I'm pondering how one would do accelerated reliability/life testing for the acoustic heat pump application. Maybe they have good-enough FEA/multiphysics on a suspension and cone, and strain/life curves they are prepared to trust. With a slope on log-log strain vs life they might project how much to overpower/overstrain for an e.g. 1000hr accelerated test.

[1] https://www.avforums.com/threads/speaker-life-expectancy.164...

thank you very much

Thanks. I was trying to square the very first sentence of the article "Equium has developed a new thermo-acoustic heat pump core that reportedly produces 3 kW to 4 kW of heat for every kilowatt of power it consumes." for not violating the first rule of thermodynamics.

Yes, this regularly comes up with any heat pump discussion. Strictly speaking, it is not producing heat, it is moving heat from outside to inside (or vice versa for an air conditioner, or for that matter, a refrigerator).

⅔ to ¾ of it anyway

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