The setup:
Injection of pressurized, cold, fluid water with P_water, T_water into
pressurized hot air with P_air, T_air (First approach P_water = P_air).
The water will partly evaporate and so its partial pressure will increase.
Contrary the air is cooled and its pressure decreases. The question is
the resulting total pressure,
temperature of the mixture, amount of evaporated and liquid water.
I tried the set up with a mixer. The resulting pressure in the outlet
material stream is always the same as in the inlet streams.
So the model seems to be wrong. Any suggestion what to do?
Thank you and regards
Thomas
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Hi Thomas,
the outlel pressures is defined by the operation mode of the mixer. You may specify the minimum, maximum or average pressure of the inlet streams. Taking this resulting pressure a PH flash is executed to calculate the resulting temperature of the outlet stream.
Gregor
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a. What does it mean "operation mode" of the mixer?
What are the different modes? Where to configure?
b. Where to configure minimum, maximum or average pressure of the inlet streams?
In the property section with 1. Conditions, 2. Molar Composition, 3. Properties ..
I see no way to specify P_min, P_max, P_av
Thomas
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Hi Thomas,
you will find this parameter in section 2 "Pressure downstream".
I prepared a sample to see the working of that.
I assumed a isenthalpic mixture - meaning there is no exchange of engergy to the environment. In this case you may use the mixer object like in my sample.
If you rather want to overwrite either pressure or temperature (or both) to a certain value the isenthalpic criteria is not valid any longer anymore. You have the use the flash vessel object instead with a energy stream attached. Here you may define the desired pressure and temperature and a PT-flash is executed for the outlet stream. You will find this version in the sample as well.
My guess is that this is a constant volume problem. DWSIM isn't capable of solving this type of operation directly, but you can use an Excel or Script unit operation and do the calculations by yourself.
Maybe this would be solved by a Volume-Enthalpy Flash calculation. Constant total volume and no heat loss (Q = 0), result is equilibrium pressure and temperature...
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@ Gregor
Thank you for your sample.
1. As I explained in the previous psot the results from the mixer simulation don't make sense.
2. Its the same with the results from the separator vessel. If changing temperatures and pressures of the inlet streams the pressure of the outlet streams are constant at 2,5 bar.
@ Daniel
What do you mean with "you can do the calculation by yourself"? In the scope of Dwsim?
If so: Do you have an example for the setup of a script unit operation?
Thomas
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Hi,
I am new to Dwsim.
The setup:
Injection of pressurized, cold, fluid water with P_water, T_water into
pressurized hot air with P_air, T_air (First approach P_water = P_air).
The water will partly evaporate and so its partial pressure will increase.
Contrary the air is cooled and its pressure decreases. The question is
the resulting total pressure,
temperature of the mixture, amount of evaporated and liquid water.
I tried the set up with a mixer. The resulting pressure in the outlet
material stream is always the same as in the inlet streams.
So the model seems to be wrong. Any suggestion what to do?
Thank you and regards
Thomas
Hi Thomas,
the outlel pressures is defined by the operation mode of the mixer. You may specify the minimum, maximum or average pressure of the inlet streams. Taking this resulting pressure a PH flash is executed to calculate the resulting temperature of the outlet stream.
Gregor
Hi Gregor,
thank you.
a. What does it mean "operation mode" of the mixer?
What are the different modes? Where to configure?
b. Where to configure minimum, maximum or average pressure of the inlet streams?
In the property section with 1. Conditions, 2. Molar Composition, 3. Properties ..
I see no way to specify P_min, P_max, P_av
Thomas
Hi Thomas,
you will find this parameter in section 2 "Pressure downstream".
I prepared a sample to see the working of that.
I assumed a isenthalpic mixture - meaning there is no exchange of engergy to the environment. In this case you may use the mixer object like in my sample.
If you rather want to overwrite either pressure or temperature (or both) to a certain value the isenthalpic criteria is not valid any longer anymore. You have the use the flash vessel object instead with a energy stream attached. Here you may define the desired pressure and temperature and a PT-flash is executed for the outlet stream. You will find this version in the sample as well.
Gregor
Last edit: Gregor Reichert 2016-03-06
My guess is that this is a constant volume problem. DWSIM isn't capable of solving this type of operation directly, but you can use an Excel or Script unit operation and do the calculations by yourself.
Maybe this would be solved by a Volume-Enthalpy Flash calculation. Constant total volume and no heat loss (Q = 0), result is equilibrium pressure and temperature...
@ Gregor
Thank you for your sample.
1. As I explained in the previous psot the results from the mixer simulation don't make sense.
2. Its the same with the results from the separator vessel. If changing temperatures and pressures of the inlet streams the pressure of the outlet streams are constant at 2,5 bar.
@ Daniel
What do you mean with "you can do the calculation by yourself"? In the scope of Dwsim?
If so: Do you have an example for the setup of a script unit operation?
Thomas