I am starting to use dwsim, because i needed to make some simulations with flash calculations.
One thing that i was needing, and couldn't find, is a way of defining the percentage of the entrance molar flow, that should be recovered as a gas.
Is there any way of defining this?
If not, is there any way of implementing it in a future release?
Thanks
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You can use a heater in the inlet of the vessel, defining the calculation mode as "outlet vapor fraction" or change the inlet stream specification directly to Temperature/Vapor Fraction or Pressure/Vapor Fraction, specifying the desired vapor fraction, then the separator will just split the phases in the inlet stream.
Regards,
Daniel
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I tryed as you told.
Guessing this is not a very pratical way of doing it, and also, having some troubles.
When i do it, i define the inlet stream composition, and add a separation vessel to calculate the outlet streams composition.
What i notice is the following:
The vapor outlet stream has the same molar flow has the inlet, and the liquid outlet stream has a molar flow of 0.
I can't have an easy access to the outlet stream composition.
In my opinion, the recuperation should be an option of the vessel, as it would make it a lot easyer to use.
Thanks
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It seems i found the problem
At the flash operation temperature, all the mixture was beeing evaporated
But, after i lowered the temperature of the flash chamber, eve defining the fraction of vapor, it didnt work, i had to set an adjust point, so it would adjust the temperature of the flash
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
You don't have to override separation temperature and/or pressure. Just make sure that the inlet stream has two or more phases, then the separator will just split them into independent streams, with the corresponding amounts. Like I've wrote before, an easy way to do that is to change the stream specification to T/VF or P/VF, and then set the vapor fraction to the value that you want. See the attached screenshot.
As far as I know, in real life a separator just does as the name says, it separates the phases resulting from a mixture of its inlets. The separator model in DWSIM is not a "Flash vessel" as you were expecting because the equilibrium calculations are also carried out in every material stream, not only in the unit operations, so it would be redundant. HYSYS and UNISIM also work this way.
Anyway, You have the option to override temperature and/or pressure but that will break the flowsheet mass balance.
Desculpa insistir neste assunto, mas acho que uma camara flash, seria um bom investimento, para equipamento a adicionar numa futura versão. Poderia ser uma camara flash simples, como as que existem nos software pagos (Aspen).
Achas que seria possivel?
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi,
I am starting to use dwsim, because i needed to make some simulations with flash calculations.
One thing that i was needing, and couldn't find, is a way of defining the percentage of the entrance molar flow, that should be recovered as a gas.
Is there any way of defining this?
If not, is there any way of implementing it in a future release?
Thanks
Hi,
You can use a heater in the inlet of the vessel, defining the calculation mode as "outlet vapor fraction" or change the inlet stream specification directly to Temperature/Vapor Fraction or Pressure/Vapor Fraction, specifying the desired vapor fraction, then the separator will just split the phases in the inlet stream.
Regards,
Daniel
I tryed as you told.
Guessing this is not a very pratical way of doing it, and also, having some troubles.
When i do it, i define the inlet stream composition, and add a separation vessel to calculate the outlet streams composition.
What i notice is the following:
The vapor outlet stream has the same molar flow has the inlet, and the liquid outlet stream has a molar flow of 0.
I can't have an easy access to the outlet stream composition.
In my opinion, the recuperation should be an option of the vessel, as it would make it a lot easyer to use.
Thanks
It seems i found the problem
At the flash operation temperature, all the mixture was beeing evaporated
But, after i lowered the temperature of the flash chamber, eve defining the fraction of vapor, it didnt work, i had to set an adjust point, so it would adjust the temperature of the flash
You don't have to override separation temperature and/or pressure. Just make sure that the inlet stream has two or more phases, then the separator will just split them into independent streams, with the corresponding amounts. Like I've wrote before, an easy way to do that is to change the stream specification to T/VF or P/VF, and then set the vapor fraction to the value that you want. See the attached screenshot.
As far as I know, in real life a separator just does as the name says, it separates the phases resulting from a mixture of its inlets. The separator model in DWSIM is not a "Flash vessel" as you were expecting because the equilibrium calculations are also carried out in every material stream, not only in the unit operations, so it would be redundant. HYSYS and UNISIM also work this way.
Anyway, You have the option to override temperature and/or pressure but that will break the flowsheet mass balance.
Regards,
Daniel
Last edit: Daniel Medeiros 2014-04-12
I see.
Maybe a flash drum could be a nice piece of equipment in another version
Desculpa insistir neste assunto, mas acho que uma camara flash, seria um bom investimento, para equipamento a adicionar numa futura versão. Poderia ser uma camara flash simples, como as que existem nos software pagos (Aspen).
Achas que seria possivel?
É possível sim. Como seria o modelo deste vaso flash, que recursos ele deveria fornecer e que tipo de opções estariam disponíveis ao usuário?