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I need equations to calculate these cryogenic problems:

  • Generally how much energy (joules) is required to convert room temperature (21 °C) nitrogen gas into 1 liter LN2 using Joule–Thomson effect ?

  • Is there a more energy-efficient way to do that ?

  • How much will cost to convert 1 liter vaporized nitrogen into liquid again in it's very low temperature right after vaporization above −195.79 °C ?

wuka
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  • Another method that may be "easier" if not more efficient is a "turbo expander" - a turbine driven by the gas flow and performing work on a load which can be outside the cooled space. An air powered die grinder driving a "fan" may be suitable. Some such grinders have coaxial input/output lending themselves to counterflow heat exchange, – Russell McMahon May 26 '15 at 15:16

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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 be working with. I assume you want to have liquified nitrogen at 1 atm. What that will cost you depends on the pressure you start with and how you achieve that.

There are multiple instructions on the web in order to liquify nitrogen at low costs. You might want to check them out.

idkfa
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