1D Flow with Heat Addition

amin.z · November 25, 2013, 12:29

Hello dear engineers!

In first I must say that my English language is week! excuse me!

I'm modeling a thin air flow in a simple path like a simple channel.
Section of path is a rectangle.
The inlet condition: Mach=0.2, P=1 atm, T=273 K
and Heat is adding to the flow from top & bottom ( q=10^6 J/Kg)
I have modeled the top & bottom in CFX-Pre as wall with heat transfer and
I use mass rate for changing the "q: (J/Kg) " to "heat flux: (W/m^2)"
But when I run CFX-Solver it exit with return code 225!

1- Is selecting the top & bottom as wall correct?
2- Is the changing I did true?
3- What is cause of error in your opinion ?

thank you!

ghorrocks · November 25, 2013, 16:09

Can you explain what the heat flow is? What does q=10^6 J/kg mean? Per kilogram of what?

amin.z · November 26, 2013, 09:05

Quote:

Originally Posted by ghorrocks

Can you explain what the heat flow is? What does q=10^6 J/kg mean? Per kilogram of what?

consider a simple channel with triangle section. Heat is adding per mass of air that flow in channel .It's adding from up & down of channel. I have the inlet condition and want to find the Mach and pressure in outlet.

ghorrocks · November 26, 2013, 16:58

I do not know of a system where the heat transfer to the fluid is proportional to the mass flow rate. My question is that this sounds like a non-physical system and then it only makes sense that modelling it is difficult.

If there is a constant heat input at the wall then use a heat flux boundary. If constant temperature then use constant temperature. There are also convective boundaries it that is suitable.

myaccount · January 17, 2014, 10:57

Hi everyone!!!

I am trying to simulate a 1d heat transfer in a medium confined between two large walls (top and bottom wall). I created a 2d rectangle in icem cfd. For top and bottom lines I have given the boundary conditions as walls. But I am not clear what boundary condition I should use for left and right lines which are not supposed to be present. (I created them only for meshing)..

Pls reply.

ghorrocks · January 18, 2014, 04:04

Have a look at what the CFX tutorials do for the simulations where they need to put outer boundaries on which are not physically present.

November 25, 2013, 12:29	1D Flow with Heat Addition	#1
amin.z Senior Member Amin Join Date: Oct 2013 Location: Germany Posts: 397 Rep Power: 14	Hello dear engineers! In first I must say that my English language is week! excuse me! I'm modeling a thin air flow in a simple path like a simple channel. Section of path is a rectangle. The inlet condition: Mach=0.2, P=1 atm, T=273 K and Heat is adding to the flow from top & bottom ( q=10^6 J/Kg) I have modeled the top & bottom in CFX-Pre as wall with heat transfer and I use mass rate for changing the "q: (J/Kg) " to "heat flux: (W/m^2)" But when I run CFX-Solver it exit with return code 225! 1- Is selecting the top & bottom as wall correct? 2- Is the changing I did true? 3- What is cause of error in your opinion ? thank you!

January 17, 2014, 10:57	Problem with 1D problem	#5
myaccount Member Join Date: Dec 2013 Posts: 53 Rep Power: 12	Hi everyone!!! I am trying to simulate a 1d heat transfer in a medium confined between two large walls (top and bottom wall). I created a 2d rectangle in icem cfd. For top and bottom lines I have given the boundary conditions as walls. But I am not clear what boundary condition I should use for left and right lines which are not supposed to be present. (I created them only for meshing).. Pls reply.

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November 25, 2013, 16:09		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Can you explain what the heat flow is? What does q=10^6 J/kg mean? Per kilogram of what?

November 26, 2013, 16:58		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I do not know of a system where the heat transfer to the fluid is proportional to the mass flow rate. My question is that this sounds like a non-physical system and then it only makes sense that modelling it is difficult. If there is a constant heat input at the wall then use a heat flux boundary. If constant temperature then use constant temperature. There are also convective boundaries it that is suitable.

January 18, 2014, 04:04		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Have a look at what the CFX tutorials do for the simulations where they need to put outer boundaries on which are not physically present.