# 1D Flow with Heat Addition

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 November 25, 2013, 13:29 1D Flow with Heat Addition #1 Senior Member     Amin Join Date: Oct 2013 Location: Germany Posts: 377 Rep Power: 8 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!

 November 25, 2013, 17:09 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,339 Rep Power: 110 Can you explain what the heat flow is? What does q=10^6 J/kg mean? Per kilogram of what?

November 26, 2013, 10:05
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Amin
Join Date: Oct 2013
Location: Germany
Posts: 377
Rep Power: 8
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.

 November 26, 2013, 17:58 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,339 Rep Power: 110 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 17, 2014, 11:57 Problem with 1D problem #5 Member   Join Date: Dec 2013 Posts: 53 Rep Power: 6 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.

 January 18, 2014, 05:04 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,339 Rep Power: 110 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.

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