Necessary Properties for heat transfer

M29 · January 7, 2020, 21:09

Hello!

I use CFX to simulate heat transfer in dry cask.

To put it simply, I want to simulate heat transfer between solid and fluid domain.

I will use ideal helium gas in fluid domain and carbon steel and stainless steel in solid domain.

But I know only density, thermal conductivity, thermal expansion coefficient, and specific heat for carbon and stainless steel.

E.g. I don't know molar mass, Ref. specific enthalpy and so on.. in cfx property tap.

So, i want to know the necessary properties to simulate heat transfer between solid and fluid domain...

Gert-Jan · January 8, 2020, 02:51

Molar mass is only relevant for Helium since the density is derived from it. For steel, density is fixed. You don't have worry about Enthalpies. For most cases, these are irrelevant. Set them to 0.

M29 · January 8, 2020, 11:25

Quote:

Originally Posted by Gert-Jan

Molar mass is only relevant for Helium since the density is derived from it. For steel, density is fixed. You don't have worry about Enthalpies. For most cases, these are irrelevant. Set them to 0.

First of all, thank you for your answer.

Can i ask something about your answer?

If the steel density is the function of temperature, is it no matter??

And, do you know when the enthalpies use?

Gert-Jan · January 8, 2020, 13:21

If you have density function that depends on temperature, then it depends on temperature. Not on molar mass.
Enthalpy is just a reference state from which temperatures are derived.

If you don't trust it, just do a test where you change the parameters and see what you get.

evcelica · January 8, 2020, 13:33

Density should be constant to account for all solid mass, unless you are modeling the change in size as part of the analysis, which I'm sure you are not, as this would then be a 2 way FSI.

If this is steady state then density and specific heat won't matter for solid domains, they only effect transient results.

M29 · January 13, 2020, 02:11

Quote:

Originally Posted by Gert-Jan

If you have density function that depends on temperature, then it depends on temperature. Not on molar mass.
Enthalpy is just a reference state from which temperatures are derived.

If you don't trust it, just do a test where you change the parameters and see what you get.

Thank you!! I will try that.

M29 · January 13, 2020, 02:16

Quote:

Originally Posted by evcelica

Density should be constant to account for all solid mass, unless you are modeling the change in size as part of the analysis, which I'm sure you are not, as this would then be a 2 way FSI.

If this is steady state then density and specific heat won't matter for solid domains, they only effect transient results.

I can't understand exactly.. but density and specific heat in solid are not necessary to simulate heat transfer between solid and fluid domain, aren't you?

Gert-Jan · January 13, 2020, 04:15

It all depends on: "What question are you trying to answer using CFD?".
Please answer this.

If you don't need to know the temperature in the solid, then you don't need these properties. If you need to include the temperature distribution in the solid, then you need to provide density and specific heat. But probably not as a function of whatsoever. If your temperature range is limited, then their influence will be limited.

Again, it all comes doen to the questions: "What question are you trying to answer using CFD?". You need to know for your self what you can ignore, and what not. We at this forum don't know if you are not clear about the EXACT problem you are trying to solve.

January 7, 2020, 21:09	Necessary Properties for heat transfer	#1
M29 New Member Sumin Park Join Date: Jul 2019 Posts: 26 Rep Power: 6	Hello! I use CFX to simulate heat transfer in dry cask. To put it simply, I want to simulate heat transfer between solid and fluid domain. I will use ideal helium gas in fluid domain and carbon steel and stainless steel in solid domain. But I know only density, thermal conductivity, thermal expansion coefficient, and specific heat for carbon and stainless steel. E.g. I don't know molar mass, Ref. specific enthalpy and so on.. in cfx property tap. So, i want to know the necessary properties to simulate heat transfer between solid and fluid domain...

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January 8, 2020, 02:51		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	Molar mass is only relevant for Helium since the density is derived from it. For steel, density is fixed. You don't have worry about Enthalpies. For most cases, these are irrelevant. Set them to 0.

January 8, 2020, 13:21		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	If you have density function that depends on temperature, then it depends on temperature. Not on molar mass. Enthalpy is just a reference state from which temperatures are derived. If you don't trust it, just do a test where you change the parameters and see what you get.

January 8, 2020, 13:33		#5
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,167 Rep Power: 23	Density should be constant to account for all solid mass, unless you are modeling the change in size as part of the analysis, which I'm sure you are not, as this would then be a 2 way FSI. If this is steady state then density and specific heat won't matter for solid domains, they only effect transient results.

January 13, 2020, 04:15		#8
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	It all depends on: "What question are you trying to answer using CFD?". Please answer this. If you don't need to know the temperature in the solid, then you don't need these properties. If you need to include the temperature distribution in the solid, then you need to provide density and specific heat. But probably not as a function of whatsoever. If your temperature range is limited, then their influence will be limited. Again, it all comes doen to the questions: "What question are you trying to answer using CFD?". You need to know for your self what you can ignore, and what not. We at this forum don't know if you are not clear about the EXACT problem you are trying to solve.