Wall temperature contours in CFD Post of CFX results

Waris6420 · November 12, 2024, 02:59

Hi! I have done multiphase simulation using RPI wall boiling model in CFX. Now I want to visualize the contours of wall temperature. There is no such variable in CFD Post. There are seperate variables for liquid and vapor wall temperature and I am not sure which one to read. I have also performed the same simulation using FLUENT and there was a variable of TEMPERATURE in those simulation results. Kindly help in this regard.

ghorrocks · November 12, 2024, 04:31

What boundary condition did you use for the wall? Or did you model the wall as a solid with conjugate heat transfer (CHT)?

(Note I am not very familiar with the RPI boiling model)

Waris6420 · November 13, 2024, 00:06

I have given heat flux at that particular wall on which i want wall temperature

evcelica · November 13, 2024, 10:58

I don't think "Wall Temperature" is ever a variable. Temperature should be the wall temperature if you are using "hybrid" values in the plot. "Conservative" would be the temperature of the first node adjacent to the wall.
I don't know if RPI makes any difference, maybe it does, I'm not 100% sure as it's been a while since I've used RPI, and I used a solid wall in my RPI model so didn't need to check.

Waris6420 · November 14, 2024, 03:31

Quote:

Originally Posted by evcelica

I don't think "Wall Temperature" is ever a variable. Temperature should be the wall temperature if you are using "hybrid" values in the plot. "Conservative" would be the temperature of the first node adjacent to the wall.
I don't know if RPI makes any difference, maybe it does, I'm not 100% sure as it's been a while since I've used RPI, and I used a solid wall in my RPI model so didn't need to check.

For hybrid, there is no variable of TEMPERATURE either. only Liquid and Vapor temperature are there seperately

evcelica · November 19, 2024, 09:50

I see.
You may have to either model the actual wall, or perhaps it is possible to form an expression for "WallTemp" using the various wall heat transfer coefficients and wall adjacent temperatures?
This is possible in single phase flow, where "WallTemp" = (Wall Heat Flux / Wall Heat Transfer Coefficient) + Temperature. This Method is listed in the FAQs: https://www.cfd-online.com/Wiki/Ansy...ficient_in_CFX

Of course, if it is even possible, it may be more difficult with your two-phase model, and you may have to use various applicable Heat Fluxes, adjacent temperatures, and HTCs, and perhaps even sum the Delta T's?
Likely much easier to just model a thin wall.

November 12, 2024, 02:59	Wall temperature contours in CFD Post of CFX results	#1
Waris6420 New Member Muhammmad Waris Join Date: May 2024 Posts: 5 Rep Power: 2	Hi! I have done multiphase simulation using RPI wall boiling model in CFX. Now I want to visualize the contours of wall temperature. There is no such variable in CFD Post. There are seperate variables for liquid and vapor wall temperature and I am not sure which one to read. I have also performed the same simulation using FLUENT and there was a variable of TEMPERATURE in those simulation results. Kindly help in this regard.

November 12, 2024, 04:31		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What boundary condition did you use for the wall? Or did you model the wall as a solid with conjugate heat transfer (CHT)? (Note I am not very familiar with the RPI boiling model) __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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November 13, 2024, 00:06		#3
Waris6420 New Member Muhammmad Waris Join Date: May 2024 Posts: 5 Rep Power: 2	I have given heat flux at that particular wall on which i want wall temperature

November 13, 2024, 10:58		#4
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,188 Rep Power: 23	I don't think "Wall Temperature" is ever a variable. Temperature should be the wall temperature if you are using "hybrid" values in the plot. "Conservative" would be the temperature of the first node adjacent to the wall. I don't know if RPI makes any difference, maybe it does, I'm not 100% sure as it's been a while since I've used RPI, and I used a solid wall in my RPI model so didn't need to check.

November 19, 2024, 09:50		#6
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,188 Rep Power: 23	I see. You may have to either model the actual wall, or perhaps it is possible to form an expression for "WallTemp" using the various wall heat transfer coefficients and wall adjacent temperatures? This is possible in single phase flow, where "WallTemp" = (Wall Heat Flux / Wall Heat Transfer Coefficient) + Temperature. This Method is listed in the FAQs: https://www.cfd-online.com/Wiki/Ansy...ficient_in_CFX Of course, if it is even possible, it may be more difficult with your two-phase model, and you may have to use various applicable Heat Fluxes, adjacent temperatures, and HTCs, and perhaps even sum the Delta T's? Likely much easier to just model a thin wall.