CFX-Turbomachinery-Use Conjugate Heat Transfer or Not?

gikamc · January 2, 2021, 09:28

Hello, Happy New Year!

I am involved in a project regarding the simulation of an axial turbine. The final purpose of the project is to specify temperature and stress distribution along blades.

The first step I have done so far is a steady-state analysis using CFX. I have imported mesh for fluid domain that I created in TurboGrid. I succeeded a good convergence plot and then imported the result for Thermal Analysis and Structural Analysis on Ansys-Mechanical.

In literature I have found that Conjugate Heat Transfer (CHT) promises more accurate results. What is the difference between direct importing of CFXs' results to Ansys Mechanical and CHT ? Is it worth to carry out CHT or the results will slightly differ from what i have done?

If CHT is worth to perform it, I know that i have to import mesh for solid domains of blades of interest and create the interfaces between solid-blade and fluid-flow. The problems i need to resolve are:

1. It turns out with an error because of similar domain that was used twice in the analysis. It was actually the blade surface and I deleted it from the flow domain and let only the inerface to take place in my model. Is that right ?

2. I defined in turbogrid tip clearance. Do i have to create a new blade in Design Modeler and cut it to the specified tip clearance or is there an automatic way to perform that ?

P.S. All I need are insights about the previous steps of that tutorial: https://www.youtube.com/watch?v=R9G8_tlz74c&t=31s

ghorrocks · January 5, 2021, 18:45

It is all a matter of what causes significant effects on something else.

The temperature of the fluid affects the blade obviously. But does the temperature of the blade affect the fluid temperature significantly? Or the flow field?

The answer to this question determines whether you can do one-way coupling (transferring the results from CFX to ANSYS Mechanical) or require two-way coupling (CHT).

gikamc · January 6, 2021, 20:27

Hello! Thank you for your reply!

In a sense of engineering understanding it seems that the turbine temperature would not affect much the flow so I think that one way fsi is proper for my case as i am concerning about temperature on rotor blades (without cooling flow).

But, in my literature survey i found related publications that use CHT even if it is about the rotor blades.

Could you please give me your insights ?

ghorrocks · January 6, 2021, 20:43

Insights on what? If you want general information then try a textbook or the literature. If you have a specific question we will try to answer it.

gikamc · January 6, 2021, 20:57

Thank you for your prompt response! If you have any suggestions for related textbooks or anything that will help my study please refer to them.

I am not searching the easy way, I really want to get all the appropriate knowledge in that field. By the way i am learning on my own, so if you have something related in mind it will save me a lot of time searching the net!

January 2, 2021, 09:28	CFX-Turbomachinery-Use Conjugate Heat Transfer or Not?	#1
gikamc New Member Join Date: May 2020 Posts: 21 Rep Power: 6	Hello, Happy New Year! I am involved in a project regarding the simulation of an axial turbine. The final purpose of the project is to specify temperature and stress distribution along blades. The first step I have done so far is a steady-state analysis using CFX. I have imported mesh for fluid domain that I created in TurboGrid. I succeeded a good convergence plot and then imported the result for Thermal Analysis and Structural Analysis on Ansys-Mechanical. In literature I have found that Conjugate Heat Transfer (CHT) promises more accurate results. What is the difference between direct importing of CFXs' results to Ansys Mechanical and CHT ? Is it worth to carry out CHT or the results will slightly differ from what i have done? If CHT is worth to perform it, I know that i have to import mesh for solid domains of blades of interest and create the interfaces between solid-blade and fluid-flow. The problems i need to resolve are: 1. It turns out with an error because of similar domain that was used twice in the analysis. It was actually the blade surface and I deleted it from the flow domain and let only the inerface to take place in my model. Is that right ? 2. I defined in turbogrid tip clearance. Do i have to create a new blade in Design Modeler and cut it to the specified tip clearance or is there an automatic way to perform that ? P.S. All I need are insights about the previous steps of that tutorial: https://www.youtube.com/watch?v=R9G8_tlz74c&t=31s

January 5, 2021, 18:45		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	It is all a matter of what causes significant effects on something else. The temperature of the fluid affects the blade obviously. But does the temperature of the blade affect the fluid temperature significantly? Or the flow field? The answer to this question determines whether you can do one-way coupling (transferring the results from CFX to ANSYS Mechanical) or require two-way coupling (CHT). __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

January 6, 2021, 20:43		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	Insights on what? If you want general information then try a textbook or the literature. If you have a specific question we will try to answer it. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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January 6, 2021, 20:27		#3
gikamc New Member Join Date: May 2020 Posts: 21 Rep Power: 6	Hello! Thank you for your reply! In a sense of engineering understanding it seems that the turbine temperature would not affect much the flow so I think that one way fsi is proper for my case as i am concerning about temperature on rotor blades (without cooling flow). But, in my literature survey i found related publications that use CHT even if it is about the rotor blades. Could you please give me your insights ?

January 6, 2021, 20:57		#5
gikamc New Member Join Date: May 2020 Posts: 21 Rep Power: 6	Thank you for your prompt response! If you have any suggestions for related textbooks or anything that will help my study please refer to them. I am not searching the easy way, I really want to get all the appropriate knowledge in that field. By the way i am learning on my own, so if you have something related in mind it will save me a lot of time searching the net!