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Topic: How do superfluids and normal fluids interact?  (Read 859 times)

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Offline Cwm9

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How do superfluids and normal fluids interact?
« on: February 24, 2019, 04:59:36 AM »
Suppose I compress CO2 and N2 at 35 bar at 0c.

I'd expect the CO2 to liquify and the N2 to be supercritical.

Does the supercritical fluid sit on top of the liquid since it is of lower density?
« Last Edit: February 24, 2019, 05:12:41 AM by Cwm9 »

Offline Enthalpy

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Re: How do superfluids and normal fluids interact?
« Reply #1 on: February 25, 2019, 05:38:32 AM »
Instead of "supercritical", you can say "gas" for N2.

35bar and 0°C is a boiling condition for CO2. At equilibrium, you would have a partial pressure of 35bar CO2 vapour in the gas phase, to which a partial pressure of N2 gas adds, so equilibrium is impossible.

The out-of-equilibrium proportions depend on the process and are more difficult to determine. If for instance CO2 is fully liquefied at 35bar and 0°C and you add N2 at 35bar and 0°C too, then liquid CO2 will stay at the bottom and gaseous N2 on the top, but CO2 evaporates slowly (without boiling if the pressure exceeds the liquid-vapour equilibrium pressure) and the total pressure rises above 35bar, for instance towards 70bar if the volume is constant.

"Superfluid" has a different meaning.

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