Energy Conversion With Supercritical Fluids

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Discussion Overview

The discussion revolves around the conversion of thermal energy into kinetic energy using supercritical fluids, specifically focusing on the dynamics within a closed system designed to facilitate this energy transfer. Participants explore the implications of achieving supercritical states and the associated velocities of molecules in such systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes a system where CO2 is maintained at pressures conducive to a supercritical state, suggesting that thermal energy can be converted into kinetic energy as the state changes.
  • Another participant challenges the assumption that nearly supercritical fluids are frictionless, asserting that this is not the case.
  • A subsequent reply indicates a misunderstanding between supercritical fluids and superfluids, clarifying that they exhibit different properties, particularly regarding viscosity.
  • One participant expresses confusion about the relationship between supercritical states and molecular velocities, questioning whether increased velocities can be achieved through heat transfer.
  • A participant mentions finding a research paper that may provide clarity on the topic, indicating ongoing exploration of the subject matter.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the properties of supercritical fluids, particularly in relation to friction and viscosity. There is no consensus on the implications of these properties for energy conversion and molecular velocities.

Contextual Notes

Participants have differing interpretations of the behavior of supercritical fluids versus superfluids, which may affect their understanding of the energy conversion process. The discussion reflects a range of assumptions and interpretations that remain unresolved.

Benign Paradigm
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Technically, this isn't a question concerning supercritical fluids. It's more about converting thermal energy into velocity by playing "keep-away" with molecules that want to go supercritical.

The idea is simple. In an fully contained system, we can more or less say volume is static. Temperature becomes what determines both pressure and state of matter once we have that system of static volume. We can now simulate the introduction and removal of thermal energy.

Let's say our system is a figure-8 loop and contains CO2 at the right pressure to invoke a super-critical state relatively near to ambient external temperatures. We can now introduce a low-energy heat source to generate a state change with relative ease. As the CO2 begins to go supercritical, we can introduce a low-energy source of cooling to from outside of this closed system, as well.

What I'd like to know is how to describe the transfer of this energy. It seems to me, that an unnaturally large portion of the thermal energy we introduce will be converted directly into kinetic energy until it leaves the system as thermal energy again on the "cooling side" of our figure-8.

I'm trying to determine the potential velocity of molecules within this system, based on the differential between my source of heat and my heat absorption. I'm just not sure exactly how to go about such a thing. Supercritical fluids are purportedly frictionless, but a system that is very nearly supercritical should be very nearly frictionless correct?

If that's the case, shouldn't it be hypothetically possible to generate extreme velocities within this system by increasing both the heat source and heat absorption rates to high levels?

And if so, how do we trend these rates to accurately achieve a desired velocity?
 
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Benign Paradigm said:
Supercritical fluids are purportedly frictionless, but a system that is very nearly supercritical should be very nearly frictionless correct?
In a word? "No."
 
Bystander said:
In a word? "No."
My understanding was that matter in the containment will reach greater velocities than it normally would, if the rest of the volume is near to reaching a supercritical state.

Judging by the simplicity of your answer, am I to assume that I'm completely wrong?
 
You have confused "supercritical" with "superfluid," as in He II is a low/zero viscosity "superfluid."
 
I see. I was taught that an entire volume must be undergo the change to a super-critical state in order for the super-critical fluid to be relaxed. For that reason, I drew a parallel to super fluids. I was with the impression that matter undergoing the change to a super-critical state would increase in velocity to transfer heat out of the volume by exhibiting the same defiance of friction.

I think I found a paper that'll adequately answer my mangled question. Maybe you'll be interested.

https://www.researchgate.net/profile/Pierre_Carles3/publication/235528431_Relaxation_of_a_supercritical_fluid_after_a_heat_pulse_in_the_absence_of_gravity_effects_Theory_and_experiments/links/00b49537191b169ed3000000.pdf
 
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Thankee.
 

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