heat flux vectors

keeper · May 2, 2012, 05:14

Dear all,

I need to display heat flux vectors in a domain but in variables menu there is no heat flux option.

Could it be solved by the expression? Which expression should I use? q = lambda * deltaT?

Please help.

Thanks for all answers.

Best Regards

ghorrocks · May 2, 2012, 18:24

That is because heat flux is not a vector quantity. It is a scalar.

keeper · May 3, 2012, 04:23

Thanks for reply but if I want to display "path" of the heat going through the domain from warmer to colder position, how should I call it? because this is what I would like to see..

keeper · May 3, 2012, 07:25

this is what I meant. It is done in Mechanical Thermal and I would like to have the same vectors in CFX.

ghorrocks · May 3, 2012, 07:25

Then you want the gradient of the temperature, enthalpy or something similar. Have a look in the "..." variables in CFD-Post and look for temperature.grad.

keeper · May 3, 2012, 07:59

I want to have exactly the same thing which is displayed on the image above. No temperatures, no enthalpy. I know that in CFX you are able to display heat flux on the walls only, that is why it is scalar. But inside the solid domain there must be some way how to do that.

ghorrocks · May 3, 2012, 08:46

The gradient of temperature is proportional the heat flux.

keeper · May 4, 2012, 06:28

thanks glenn, I displayed temperature gradient and it seems to be ok but I think that it shows vectors conversly (Vectors are in direction from colder to hotter position). Can I switch the direction somehow?

Thank you for your replies.

ghorrocks · May 4, 2012, 06:34

You can generate a user defined variable in CFD-Post which has the inverse of the components, U component = -temperature.grad U etc.

keeper · May 4, 2012, 07:12

thanks a lot again, appreciate your help

May 2, 2012, 05:14	heat flux vectors	#1
keeper Senior Member Join Date: Jul 2010 Posts: 152 Rep Power: 15	Dear all, I need to display heat flux vectors in a domain but in variables menu there is no heat flux option. Could it be solved by the expression? Which expression should I use? q = lambda * deltaT? Please help. Thanks for all answers. Best Regards

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May 2, 2012, 18:24		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	That is because heat flux is not a vector quantity. It is a scalar.

May 3, 2012, 04:23		#3
keeper Senior Member Join Date: Jul 2010 Posts: 152 Rep Power: 15	Thanks for reply but if I want to display "path" of the heat going through the domain from warmer to colder position, how should I call it? because this is what I would like to see..

May 3, 2012, 07:25		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Then you want the gradient of the temperature, enthalpy or something similar. Have a look in the "..." variables in CFD-Post and look for temperature.grad.

May 3, 2012, 07:59		#6
keeper Senior Member Join Date: Jul 2010 Posts: 152 Rep Power: 15	I want to have exactly the same thing which is displayed on the image above. No temperatures, no enthalpy. I know that in CFX you are able to display heat flux on the walls only, that is why it is scalar. But inside the solid domain there must be some way how to do that.

May 3, 2012, 08:46		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	The gradient of temperature is proportional the heat flux.

May 4, 2012, 06:28		#8
keeper Senior Member Join Date: Jul 2010 Posts: 152 Rep Power: 15	thanks glenn, I displayed temperature gradient and it seems to be ok but I think that it shows vectors conversly (Vectors are in direction from colder to hotter position). Can I switch the direction somehow? Thank you for your replies.

May 4, 2012, 06:34		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	You can generate a user defined variable in CFD-Post which has the inverse of the components, U component = -temperature.grad U etc.

May 4, 2012, 07:12		#10
keeper Senior Member Join Date: Jul 2010 Posts: 152 Rep Power: 15	thanks a lot again, appreciate your help