Conjugate heat transfer - Free convection

delaneyluke · May 16, 2011, 12:23

Hi Guys,
I know the title seems like something discussed a dozen times before but hear me out please.
I've got the wall of a cooler, so cold air inside and ambient outside. Wall consists of steel and insulation. A simple heat balance gives me the heat flux and convective htc's (inside and outside)
Now attempting a 2D comparison with fluent and am just not able to match the htc's calculated, not even close.
It's purely laminar with a rayleigh number in the power of 10^3 on both sides. So have been running a 2D laminar sim with fixed values of temp for the inside and outside fluid domains.
I've tried constant dens, bousinesq and ideal gas but to no avail. Temp diff between outside and inside is around 20 degC.
I've considered a BL mesh to capture the thermal BL at the surfaces, adjusted relaxation parameters but htc's just dont come close.

Any suggestion please.

Regards
LD

oky · May 25, 2011, 00:14

Hi everyone,

I need help, how to get the value of convection coefficient [h] from Fluent directly?
Thank you.

Best regrads,

Oky

sandeep_tu · May 25, 2011, 06:08

@Luke

CHTC depends upon the reference temperature which u give in the REFERENCE VALUES panel. In natural convection consider the gravity and try with incompressible ideal gas(for density).

May be explain ur problem bit more detailed.

@OKY

U can get the CHTC values directly from reports--surface integrals---area wtd avg---wall flux---surface heat transfer coeff

Regards
Sandeep

May 16, 2011, 12:23	Conjugate heat transfer - Free convection	#1
delaneyluke Senior Member Join Date: Mar 2009 Location: Indiana, US Posts: 186 Rep Power: 17	Hi Guys, I know the title seems like something discussed a dozen times before but hear me out please. I've got the wall of a cooler, so cold air inside and ambient outside. Wall consists of steel and insulation. A simple heat balance gives me the heat flux and convective htc's (inside and outside) Now attempting a 2D comparison with fluent and am just not able to match the htc's calculated, not even close. It's purely laminar with a rayleigh number in the power of 10^3 on both sides. So have been running a 2D laminar sim with fixed values of temp for the inside and outside fluid domains. I've tried constant dens, bousinesq and ideal gas but to no avail. Temp diff between outside and inside is around 20 degC. I've considered a BL mesh to capture the thermal BL at the surfaces, adjusted relaxation parameters but htc's just dont come close. Any suggestion please. Regards LD

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May 25, 2011, 00:14		#2
oky New Member Oky Andytya Join Date: Nov 2010 Posts: 26 Rep Power: 16	Hi everyone, I need help, how to get the value of convection coefficient [h] from Fluent directly? Thank you. Best regrads, Oky

May 25, 2011, 06:08		#3
sandeep_tu Member Sandeep Join Date: Apr 2009 Location: Munich, Germany Posts: 30 Rep Power: 17	@Luke CHTC depends upon the reference temperature which u give in the REFERENCE VALUES panel. In natural convection consider the gravity and try with incompressible ideal gas(for density). May be explain ur problem bit more detailed. @OKY U can get the CHTC values directly from reports--surface integrals---area wtd avg---wall flux---surface heat transfer coeff Regards Sandeep