Real gas state

sxl_sxl · August 13, 2021, 07:59

Forum boss, I use real gas for simulation in FLOEFD, I have a question，how to specify the state of real gas as liquid at the entrance boundary, I hope you can help me, thank you!

In addition, can you provide me with some real gas Phase change cases

evrenykn · August 15, 2021, 09:21

Hi sxl_sxl,

I think, you can define the real gas as liquid with initial conditions of the domain. You need to check the thermodynamic data of the gas when it's liquid form.

sxl_sxl · August 20, 2021, 08:47

hi Evren
Thank you for your reply. I set the pressure and temperature in the initial conditions, but in the pressure enthalpy diagram, the saturation pressure corresponds to two states. I want to saturate the liquid, but I can’t achieve it.
Thanks for your help

Boris_M · October 6, 2021, 02:58

Hi SXL,

As Evren said, the fluids phase is depending on its temperature and pressure. So if you use a fluid that is liquid at -10°C and 2 bar, then it will be liquid for such a boundary condition if specified at the inlet.
The state of the fluid is dependent on the conditions defined in the boundary condition. At the right temperature and pressure, you will have the fluids phase for those values.

Regards,
Boris

sxl_sxl · October 11, 2021, 08:51

Hello Boris_M
In the pressure enthalpy diagram, there are two saturation states corresponding to pressure and temperature. They are saturated liquid and saturated gas respectively. I want the inlet boundary to be liquid, but after calculation, the inlet boundary appears to be gaseous, so I always have questions
Regards,
sxl

Boris_M · October 11, 2021, 11:11

Can you check if the temperature near the inlet is the same as defined in the Inlet BC?
I just heard from another case that there is a bug where the temperature is higher although differently defined in the inlet BC. This of course might then get from the liquid state into the gaseous state.

Also, do you have the Advanced module?
If you want to consider phase change in the simulation, you will need the advanced module.

Regards,
Boris

sxl_sxl · October 13, 2021, 08:55

Hello Boris_M
The inlet temperature is consistent with the boundary conditions, but it is not the desired liquid, but gas. I have an advanced module. In addition, I would like to ask, what is the relationship between the solution time of transient calculation and the time step? Is there a calculation method?
Regards,
sxl

Boris_M · October 13, 2021, 12:39

Then someone from the support team should have a look at it. It is therefore best you raise a support ticket with them and provide them the geometry.

I'm not sure I understand the question about the solution time and time step.
Can you clarify what you mean by solution time and time step and what do you want to calculate or what you are refering to.

Regard,
Boris

August 13, 2021, 07:59	Real gas state	#1
sxl_sxl New Member SUN Join Date: Jan 2018 Posts: 7 Rep Power: 8	Forum boss, I use real gas for simulation in FLOEFD, I have a question，how to specify the state of real gas as liquid at the entrance boundary, I hope you can help me, thank you! In addition, can you provide me with some real gas Phase change cases

August 15, 2021, 09:21		#2
evrenykn New Member Evren Yilmaz Yakin Join Date: Feb 2016 Location: Ankara, Turkey Posts: 27 Rep Power: 10	Hi sxl_sxl, I think, you can define the real gas as liquid with initial conditions of the domain. You need to check the thermodynamic data of the gas when it's liquid form. __________________ Best Regards, Evren

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August 20, 2021, 08:47		#3
sxl_sxl New Member SUN Join Date: Jan 2018 Posts: 7 Rep Power: 8	hi Evren Thank you for your reply. I set the pressure and temperature in the initial conditions, but in the pressure enthalpy diagram, the saturation pressure corresponds to two states. I want to saturate the liquid, but I can’t achieve it. Thanks for your help

October 6, 2021, 02:58		#4
Boris_M Disabled Join Date: Jul 2009 Posts: 616 Rep Power: 24	Hi SXL, As Evren said, the fluids phase is depending on its temperature and pressure. So if you use a fluid that is liquid at -10°C and 2 bar, then it will be liquid for such a boundary condition if specified at the inlet. The state of the fluid is dependent on the conditions defined in the boundary condition. At the right temperature and pressure, you will have the fluids phase for those values. Regards, Boris

October 11, 2021, 08:51		#5
sxl_sxl New Member SUN Join Date: Jan 2018 Posts: 7 Rep Power: 8	Hello Boris_M In the pressure enthalpy diagram, there are two saturation states corresponding to pressure and temperature. They are saturated liquid and saturated gas respectively. I want the inlet boundary to be liquid, but after calculation, the inlet boundary appears to be gaseous, so I always have questions Regards, sxl

October 11, 2021, 11:11		#6
Boris_M Disabled Join Date: Jul 2009 Posts: 616 Rep Power: 24	Can you check if the temperature near the inlet is the same as defined in the Inlet BC? I just heard from another case that there is a bug where the temperature is higher although differently defined in the inlet BC. This of course might then get from the liquid state into the gaseous state. Also, do you have the Advanced module? If you want to consider phase change in the simulation, you will need the advanced module. Regards, Boris

October 13, 2021, 08:55		#7
sxl_sxl New Member SUN Join Date: Jan 2018 Posts: 7 Rep Power: 8	Hello Boris_M The inlet temperature is consistent with the boundary conditions, but it is not the desired liquid, but gas. I have an advanced module. In addition, I would like to ask, what is the relationship between the solution time of transient calculation and the time step? Is there a calculation method? Regards, sxl

October 13, 2021, 12:39		#8
Boris_M Disabled Join Date: Jul 2009 Posts: 616 Rep Power: 24	Then someone from the support team should have a look at it. It is therefore best you raise a support ticket with them and provide them the geometry. I'm not sure I understand the question about the solution time and time step. Can you clarify what you mean by solution time and time step and what do you want to calculate or what you are refering to. Regard, Boris