Flash calculations

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Stephan
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Joined: 15 July 2020, 08:16

Flash calculations

Post by Stephan »

I have a flash unit operation in a testfile.
When I run it, the liquid outlet has a higher water flow than the condensed portion of the water in the inlet stream.
How can that be?

See attached file.
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Test Flash.fsd
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jasper
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Re: Flash calculations

Post by jasper »

The document you posted seems to only contain compressor units - can you check whether you attached the right document?
Stephan
Posts: 46
Joined: 15 July 2020, 08:16

Re: Flash calculations

Post by Stephan »

Indeed, I atached the wrong file. Here is the right one.
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Flash Test.fsd
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jasper
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Re: Flash calculations

Post by jasper »

At 1.634999 bar and 78 C, water is liquid. The vapor pressure for water at 78 C is 0.43703103 bar.

However, mix it with enough air and enough water goes into the vapor phase. Your vapor molar flow rate is 16.5x higher than your liquid molar flow rate. Water mole fraction in the vapor phase is roughly 27%, which, from a quick google search (https://www.engineeringtoolbox.com/maxi ... _1403.html) is not unreasonable?
Stephan
Posts: 46
Joined: 15 July 2020, 08:16

Re: Flash calculations

Post by Stephan »

Indeed, I was wrong.
I just misinterpreted the stream informations.
The flash unit behaves as it should.
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jasper
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Re: Flash calculations

Post by jasper »

Glad to hear your issue is resolved.
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