CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Question about the inconsistent Prandtl number and Cv of water in tutorial cases

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 16, 2019, 11:35
Question Question about the inconsistent Prandtl number and Cv of water in tutorial cases
  #1
New Member
 
Tun
Join Date: Mar 2018
Posts: 12
Rep Power: 8
chengtun is on a distinguished road
Hi, everyone! I have a question about the inconsistent Prandtl number of water in tutorial cases. In the case of wallboiling of reactingEulerFoam solver in https://github.com/OpenFOAM/OpenFOAM...perties.liquid. The Prandtl number of water of liquid and gas was set at the same value, 2.289.(I wonder why the value was set the same? Is it not for the saturated phase?)
I looked up in the table and found for the pressure in simulation(p=100000Pa) and saturated phase, Pr is 1.757 for liquid and 1.015 for gas. For the pressure and initial temperature in simulation(p=100000Pa, T=368K) Pr is 1.848. All of them are different from the case value. How to explain the difference and how to set the value?
Another question is the Heat capacity at constant volume Cv is also inconsistent with actual value. Suppose p=100000Pa, for gas Cv was set at 4195 but actually is 1552.7; For liquid Cv was set at 12078.4 but actually is 3769.7; The unit is J/kg/K.
Thanks a lot for any hint!
chengtun is offline   Reply With Quote

Old   February 4, 2020, 09:53
Default
  #2
ZZW
New Member
 
Zhao
Join Date: Dec 2019
Posts: 4
Rep Power: 6
ZZW is on a distinguished road
Hi Tun,


I guess the unreal value is given to Cv because of the assumption to vapour. In the tutorial case the vapour is assumed saturated, which means that the properties remain unchanged after the vapour is generated. Therefore, an extreme high cv is given to stable the vapour temperature to suit this assumption.



Hope this would help you.


Regards,
Zao
ZZW is offline   Reply With Quote

Reply

Tags
heat capacity, prandtl number, water

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 18:52.