Conjugate Heat Transfer at a pipe

andoss · August 12, 2009, 05:00

I want to simulate a conjugate heat transfer at a pipe but I do not know how to set the boundary conditions with Ansys Cfx Pre

.
At the inlet of the pipe there is air with 350 K and a pressure of 1,2 bar and at the outlet of the pipe there should be a pressure of 1 bar. Outside the pipe (external surface) there should be a temperature of 293 K.
I have created a Domain Interface between the solid and the fluid domain.
With CFX Post I was able to see a temperature distribution within the fluid domain (in the pipe) but not in the solid domain of the pipe.
Does someone know which parameters I have to set in ANSYS Cfx Pre to get the temperature distribution in the solid domain of the pipe?

Thank you in advance,

Andi

ghorrocks · August 12, 2009, 07:07

Hi,

The timescales of the temperature in the pipe and the flow are likely to be different by orders of magnitude. That is to say the fluid flow will settle down in under a second but the pipe will take hours to come to a steady temperature.

So: Are you sure you have run it for long enough to get the pipe temperature to move significantly? If steady state are you using a solid timescale factor? Are you sure your simulation is converged? CHT simulations really need convergence on residuals AND imbalances to ensure convergence.

Glenn Horrocks

andoss · August 13, 2009, 04:57

Hi,

I increased the solid timescale, now it works

Andi

ghorrocks · August 13, 2009, 06:21

Hi,

You really need to use imbalances as a convergence critereon for these type of simulations. If you were using imbalances then you would have known that your first go had not converged.

Glenn Horrocks

csmistry · August 17, 2009, 03:24

Sir can we consider only fluid domain (considering inner dimensions of tube) and assuming canstant wall temp condition on outerwall... so there is no need of FSI and no question of steady state... am i right

ghorrocks · August 17, 2009, 08:54

If you are asking whether constant temperature boundary conditions can be applied, the answer is yes. I don't know what you mean about steady state, you will have to make the question clearer.

August 12, 2009, 05:00	Conjugate Heat Transfer at a pipe	#1
andoss New Member Andi Join Date: Aug 2009 Location: Austria/Graz Posts: 5 Rep Power: 16	I want to simulate a conjugate heat transfer at a pipe but I do not know how to set the boundary conditions with Ansys Cfx Pre . At the inlet of the pipe there is air with 350 K and a pressure of 1,2 bar and at the outlet of the pipe there should be a pressure of 1 bar. Outside the pipe (external surface) there should be a temperature of 293 K. I have created a Domain Interface between the solid and the fluid domain. With CFX Post I was able to see a temperature distribution within the fluid domain (in the pipe) but not in the solid domain of the pipe. Does someone know which parameters I have to set in ANSYS Cfx Pre to get the temperature distribution in the solid domain of the pipe? Thank you in advance, Andi davidrlc89 likes this.

August 17, 2009, 03:24	alternative	#5
csmistry Member mistry Join Date: Apr 2009 Location: India Posts: 69 Rep Power: 17	Sir can we consider only fluid domain (considering inner dimensions of tube) and assuming canstant wall temp condition on outerwall... so there is no need of FSI and no question of steady state... am i right davidrlc89 likes this.

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August 12, 2009, 07:07		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Hi, The timescales of the temperature in the pipe and the flow are likely to be different by orders of magnitude. That is to say the fluid flow will settle down in under a second but the pipe will take hours to come to a steady temperature. So: Are you sure you have run it for long enough to get the pipe temperature to move significantly? If steady state are you using a solid timescale factor? Are you sure your simulation is converged? CHT simulations really need convergence on residuals AND imbalances to ensure convergence. Glenn Horrocks

August 13, 2009, 04:57		#3
andoss New Member Andi Join Date: Aug 2009 Location: Austria/Graz Posts: 5 Rep Power: 16	Hi, I increased the solid timescale, now it works Andi

August 13, 2009, 06:21		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Hi, You really need to use imbalances as a convergence critereon for these type of simulations. If you were using imbalances then you would have known that your first go had not converged. Glenn Horrocks

August 17, 2009, 08:54		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	If you are asking whether constant temperature boundary conditions can be applied, the answer is yes. I don't know what you mean about steady state, you will have to make the question clearer.