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Phase Change of Supercritical CO2 (from liquid to supercritical fluid)
4

Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

(OP)
Hi all,

I am currently studying the application using the supercritical carbon dioxide as the process fluid. I am just wondering, will there be any problem if I introduce the carbon dioxide at liquid phase first, then only raise the temperature until the carbon dioxide becomes supercritical carbon dioxide after some time. Seriously I do not know what will happen inside the pipeline. I only know the density change will be huge. Is that anyone has the related experience over here?

Thank you for your time!

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

the density will go down as you raise the temperature (the velocity will increase).

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

what sort of temperatures and pressures are you talking about?

what lengths, flows?

The phase diagrams of pure CO2 with density are well known and easily found. Example below - scroll down for the graph.

http://what-when-how.com/nanoscience-and-nanotechn...

Mass flow will remain the same therefore if density goes down, velocity goes up.

The benefit of liquid or super critical CO2 is that the viscosity is very low.

CO2 with contaminants, even small amounts ( 1-2%) make those diagrams invalid and you need to do some specific testing.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

(OP)
Thank you all for the responses. I wished to introduce the Carbon dioxide at 20 C with a pressure of 100 barg. Then slowly heating the carbon dioxide until target temperature of 70degC at certain pressure drop like about 5 barg. So I guess I can expect the change of phase from liquid to supercritical fluid. Will there be any problem if I do so?

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

A similar experiment was done with water at a Cleaver Brooks facility some 30 years ago except pressure and temperature were much greater. At critical point, you could not distinguish liquid from vapor phase.

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

When you " first introduce the CO2 as liquid phase ", check that the pipeline is initially at a pressure that will prevent the transient formation of solid CO2 as the upstream liquid expands isenthalpically into the downstream. Else, once solid CO2 forms, it could block up the injection fitting.

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

Patchlam. I don't really understand your third sentence and can't work out what you're trying to do. Is this a flowing thing our a fixed volume? What pressure drop of 5 barg. Please explain yourself the equipment and procedure. We can't see what you can see only what you've told us so look at that and see where the gaps are.

Heating co2 at a pressure above 75odd bar will mean you transition from liquid to supercritical. Unless your volume increases then so will your pressure as the density reduces. That pressure rise could be quite big.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

(OP)
Hi LittleInch,

Thanks for your response. Yes, basically the CO2 will be flowing inside a fixed volume of pipe and the pressure will drop across the pipe.

RE: Phase Change of Supercritical CO2 (from liquid to supercritical fluid)

Beware that the viscosity of CO2 is really low and hence to get 5 bar you'll need to be flowing very fast or using some sort of pressure restriction device.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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