Thermoacoustics, liquid nitrogen, and rotary vane motors.

Discussion in 'Spare Parts, Tools & Product Developement' started by CanadaGlass, Oct 30, 2013.

  1. CanadaGlass

    CanadaGlass New Member

    New to the forum, and indeed to motorized bicycles. I bought a second hand HT mounted on a bike in real rough shape. I love it, and now I want to build something nice. This forum is a goldmine of information, and I am in the planning stages now. I expect I will build a 4 stroke in-frame of some sort, focusing on making it as quiet as possible. My dream bike would run on liquid nitrogen, and that is the point of this thread. I doubt I will tackle this any time soon, but I would like to at some point down the road...

    I have been blowing glass since 1993. Every once in a while, a piece of glass I am working on starts "singing". Known as Sondhauss oscillations, they are powered by a heat differential in the glass. This was my introduction to thermoacoustics. Like the name suggests, thermoacoustics is the study of the interplay between heat and sound. There is a non-profit out there (SCORE research) developing a wood and dung burning stove for the third world that uses the heat of the stove to generate a sound wave, and the sound wave powers a refrigerator. Along the way, it also moves a speaker which generates a trickle charge for a laptop. The most commercially viable use for thermoacoustics is in the area of cryogenic refrigeration. It used to be, cascade vapour compression refigeration was the order of the day if you wanted to liquify nitrogen. That means multiple compressors, with multiple coolant gasses, and all the losses asscosiated with such a multi-stage system. Enter thermoacoustics, and pulse-tube refrigeration. Standard refrigeration works by compressing a gas so it gets hot, allowing the heat to dissapate, and then decompressing it so it gets cold. What is a sound wave, if not a fluctuating pressure wave? A sound wave shifting back and forth in a tube can work so well as a heat pump that this is now how industrial gasses are liquified. Search "Q-drive cryocoolers" for the world leaders in this technology...

    To make a long story short, interrupt. No, wait...
    Liquid nitrogen production has become much more energy efficient, and looks like a good candidate for an energy carrier, though one major drawback is it's low energy density. No half-gallon tank is going to do the trick here...needs more like a twenty litre dewar. If the welding supply companies weren't so predatory in their pricing, it would still be cheap to fill. Price per litre is less than 10 cents to produce, but it is more a question of what the market will bear. As an example, when filling high-pressure oxygen tanks for glassblowing, I have paid as little as 12$ for a fill, but have also had them try to charge me as much as $120 per fill...

    Air motors are extremely lightweight, work well over a wide rpm range, and are quiet. Thoughts?
     

  2. CanadaGlass

    CanadaGlass New Member

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