Why hydrogen? Why not propane? Variable-position propane valves are commonplace. I'm sure you could find one that would suit your needs. But, given that you're thinking of using a "ball valve and servo" to handle a flammable gas, maybe it'd be better to leave this one be. This may be one of those projects where, if you have to ask, you shouldn't do it.
Okay, so I think I know how I'm going to do throttle, but I need to use it in a liquid fuel system anyway. So, does anyone here know how to cool stuff below -500 degrees Fahrenheit?
QuoteOkay, so I think I know how I'm going to do throttle, but I need to use it in a liquid fuel system anyway. So, does anyone here know how to cool stuff below -500 degrees Fahrenheit? no.
Well, i don't need it to be that cold. Just cold enough so i can create and store liquid hydrogen.
But, what the heck: if you really want liquid H2, just go down to your local Praxair and buy a container of it. You don't have to compress it yourself.
Quote from: WireJunky on Sep 07, 2013, 12:44 amWell, i don't need it to be that cold. Just cold enough so i can create and store liquid hydrogen. Absolute zero is: ?459.67°FBoiling point of hydrogen is:?-423.17 °FSo, yeah....you've got a little wiggle room. It will be cheaper to buy liquid hydrogen than to liquefy your own. But...if you want to try, here ya go -The critical temperature for hydrogen as 33 Kelvin. This is the maximum temperature at which hydrogen can be a liquid, no matter how great the pressure is. The process of liquefying hydrogen must therefore get it below 33 Kelvin.The critical pressure for hydrogen is about 13 atmospheres (atm). This is the minimum pressure needed to keep hydrogen a liquid at its critical temperature. These critical points provide the parameters for keeping hydrogen a liquid.The regenerative cooling process. This method pressurizes gas and allows it to expand. This allows the gas to exchange heat with its environment, thus cooling it. The gas is then passed through a heat exchanger, which cools the gas, thereby compressing it. This process is repeated until the gas cools enough to liquefy.Step 1)Apply the regenerative cooling process to liquefy hydrogen as first performed by James Dewar in 1898. Pressurize the hydrogen to 180 atm and pre-cool it with liquid nitrogen. Allow the hydrogen to expand through a valve that is also cooled by liquid nitrogen.Step 2)Repeat Step 1 until the hydrogen liquefies. Dewar's experiment yielded about 20 cubic centimeters (CCs) of liquid hydrogen, which was about 1 percent of the hydrogen in the experiment.Good luck!