Calculate heat flux direction

TrII4d · February 4, 2014, 11:39

Dear all,

is it possible to calculate the heat flux for each direction (i.e: $\dot{q}_{x}= ... , \dot{q}_{y}= ... , \dot{q}_{z}= ...$ ) ?

I want to simulate the heat transfer from a plate to ambient air ... velocity is s.th round 2 m/s ...

is there a way to do this with "Additional Variable" ? if yes, how is the workflow ? At the moment I'm just using AV for gradient calculations ...

thanks in advance !

ghorrocks · February 4, 2014, 17:22

You can calculate these heat fluxes from the thermal conductivity equation if it is a solid domain. Or is it a fluid domain?

TrII4d · February 5, 2014, 02:21

hi glenn and other cfd-user,

as supposed it's a fluid domain ... but i'm calculating the fluid with $\lambda = const.$ ... so i can use the thermal conductivity equation for my fluid, too ?! or am i wrong ?

thanks in advance !

ghorrocks · February 5, 2014, 05:27

In a solid domain you can get the thermal fluxes from the gradient of temperature in the body as the only heat transfer is from conduction. But in a fluid you have conduction and convection, and possibly other mechanisms as well. I guess you can look at the temperature (or enthalpy) gradient here too.

TrII4d · February 5, 2014, 11:15

hi glenn,

its always nice to hear your point of view ... anyway ... i assume that i have thermal conductivity in a fluid with const. thermal conductivity ... for this case i calculated my heat transfer for all three directions ... at the moment i have no verification for the results ... what i have done is that i compared the contour plot of the grad q with the streamlines (see attached)

in a further step i want to calculate the heat transfer for a 1D problem analytical and compare the value with CFX ... or does anyone has a better idea ?

- thanks

February 4, 2014, 11:39	Calculate heat flux direction	#1
TrII4d Member Join Date: Nov 2011 Location: Germany Posts: 40 Rep Power: 14	Dear all, is it possible to calculate the heat flux for each direction (i.e: $\dot{q}_{x}= ... , \dot{q}_{y}= ... , \dot{q}_{z}= ...$ ) ? I want to simulate the heat transfer from a plate to ambient air ... velocity is s.th round 2 m/s ... is there a way to do this with "Additional Variable" ? if yes, how is the workflow ? At the moment I'm just using AV for gradient calculations ... thanks in advance !

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February 4, 2014, 17:22		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You can calculate these heat fluxes from the thermal conductivity equation if it is a solid domain. Or is it a fluid domain?

February 5, 2014, 02:21		#3
TrII4d Member Join Date: Nov 2011 Location: Germany Posts: 40 Rep Power: 14	hi glenn and other cfd-user, as supposed it's a fluid domain ... but i'm calculating the fluid with $\lambda = const.$ ... so i can use the thermal conductivity equation for my fluid, too ?! or am i wrong ? thanks in advance !

February 5, 2014, 05:27		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	In a solid domain you can get the thermal fluxes from the gradient of temperature in the body as the only heat transfer is from conduction. But in a fluid you have conduction and convection, and possibly other mechanisms as well. I guess you can look at the temperature (or enthalpy) gradient here too.