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The combustion chamber and nozzle of the Space Shuttle main engine were cooled with liquid hydrogen. Liquid hydrogen was also the fuel. It was used as a coolant before it was burned (regenerative cooling). Another example is the air breathing rocket engine SABRE. Here too liquid hydrogen is used as fuel. It's also used for liquefying the atmospheric ...

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Gaseous hydrogen is often used to cool the large generators in power plants. "Hydrogen’s low gas density, high specific heat, and high thermal conductivity" are listed in the GE link as the major drivers behind its use. For instance: http://en.wikipedia.org/wiki/Hydrogen-cooled_turbo_generator http://www.control.com/thread/1267097548 https://powergen....

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There is no way to get around the physics in this case. The fundamental issue here is that peltier effect refrigerators are individually extremely inefficient, and stacking them in essence "stacks" their inefficiencies. Why are they inefficient? Because the material they are made from ideally should have zero electrical resistance and infinite thermal ...

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Internal energy is a measure of the distribution of translation, rotation, and vibration in the molecules. A liquid has far less in translational and rotational energy per molecule. As proof, consider that $$\tilde{U}_{vap} - \tilde{U}_{liq} = \Delta_{vap}\tilde{U} = \Delta_{vap}\tilde{H} - \Delta_{vap}(p\tilde{V})$$ For an ideal gas, $\Delta_{vap}(p\... 2 Does the stacking of peltiers device shows promising results in achieving the cryogenic temperature? If you consider actually working in devices that are working in satellites to be "promising", then yes. I have tried doing the experiment, the overall temperature of the system increased around 80ºC and then the dissipation of that heat was the prime ... 1 You are after a method to reduce a position or temperature variation in thermal conductivity to one value over the entire object. You want to substitute this one value into series + parallel thermal resistance equations. The starting theoretical formulation for heat flow$\dot{q}$(W) through an area$A$(m$^2$) in a material at a temperature$T$(K) with a ... 1 If you like living, do not attempt to build your own high-pressure LN2 tank if you have never designed commercial-grade pressure vessels before. Use this. 1 Short answer is no, as other commenters have suggested. The best solution is a small Dewar flask, which is stainless steel. Depending on how much you need, a commercial Thermos could do in a pinch. (Edit: I saw you want to use this for a tank on your rocket. If you are using it for a tank, there is not much in the cheap+light phase space. Cheap would be ... 1 If I am not mistaken the answer to your first question would be none.$\mu_{JT} = \frac{\partial T}{\partial p}|_H\$ shows that that the conversion takes place under circumstances with no change in enthalpy. This does not mean however that you do not need energy for the process. However I can't answer that because you did not specify what pressures you will ...

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I debated between Answer or Comment on this, but ultimately I think it is more of an answer - albeit an imperfect answer. It sounds to me like the primary problem you are trying to solve is preventing material transfer from the balls/cups etc. during the ball milling process. I don't think you necessarily need to change materials, and perhaps could even ...

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If cost isn't an extreme object, then hou might have lowest contamination by using a Co+WC makeup for your balls, and use a cryoplastic cup to avoic abraiding between balls & cup. The WC is extremely thermally stable & has an incredibly high surface hardness (not to mention density). As long as your Co binder could hold up to the stresses (or you ...

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