Inlet/Outlet Radiative Heat Transfer in CFX-Pre CEL Expression

meierch · October 21, 2016, 06:03

Dear all,

I would like to use the total net radiative heat transfer through inlets and outlets in a CFX-Pre CEL Expression. At walls, I can use areaInt(Wall Radiative Heat Flux)@myWall. However, this variable is not defined at inlets and outlets.

The quantity of interest is available in the solver manager monitor as "I-Radiation Boundary Flow at ...". Is there a workaround to get this value into a CEL expression?

Radiation solver is Discrete Transfer, surface to surface. (Monte Carlo is an option, if it would make a difference).

Thanks in advance!
Chris

Opaque · October 21, 2016, 12:32

Not certain, but have you tried monitoring the value in the ANSYS CFX Solver Manager ?

Add a Monitor Point, Option = Expression, Expression Value = areaInt (Wall Radiative Heat Flux)@MyInlet, and see if it produces a non-zero value, and compare to the Boundary Flow reported for the I-Radiation equation.

I agree with you that in CFD-Post that variable is not defined.

Hope the above helps,

meierch · October 24, 2016, 06:10

Thanks, Opaque. The monitored output for areaInt (Wall Radiative Heat Flux)@MyInlet is not correct. The value is non-zero but also non-sensical... sometimes correct, sometimes not, i cannot see the logic behind it.

However, I found that the quantities "Wall Irradiation Flux" and "Wall Absorbed Radiation Flux" are correct at myInlet. This is sufficient, as I can calculate the net "Wall Radiative Heat Transfer" as
Irradiation - TextBlackBody**4 * Sigma * Area.
TextBlackBody is the "External Blackbody Temperature" BC set at Inlets/Outlets.

Thanks again, Problem Solved

PS my guess is that "Wall Radiative Heat Flux" is too derived as difference between other quantities, and that at some point, the local fluid temperature is used instead of the External BB Temperature, causing the non-sensical Output ...

October 21, 2016, 06:03	Inlet/Outlet Radiative Heat Transfer in CFX-Pre CEL Expression	#1
meierch New Member christoph meier Join Date: Sep 2010 Posts: 2 Rep Power: 0	Dear all, I would like to use the total net radiative heat transfer through inlets and outlets in a CFX-Pre CEL Expression. At walls, I can use areaInt(Wall Radiative Heat Flux)@myWall. However, this variable is not defined at inlets and outlets. The quantity of interest is available in the solver manager monitor as "I-Radiation Boundary Flow at ...". Is there a workaround to get this value into a CEL expression? Radiation solver is Discrete Transfer, surface to surface. (Monte Carlo is an option, if it would make a difference). Thanks in advance! Chris

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October 21, 2016, 12:32		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,880 Rep Power: 33	Not certain, but have you tried monitoring the value in the ANSYS CFX Solver Manager ? Add a Monitor Point, Option = Expression, Expression Value = areaInt (Wall Radiative Heat Flux)@MyInlet, and see if it produces a non-zero value, and compare to the Boundary Flow reported for the I-Radiation equation. I agree with you that in CFD-Post that variable is not defined. Hope the above helps,

October 24, 2016, 06:10		#3
meierch New Member christoph meier Join Date: Sep 2010 Posts: 2 Rep Power: 0	Thanks, Opaque. The monitored output for areaInt (Wall Radiative Heat Flux)@MyInlet is not correct. The value is non-zero but also non-sensical... sometimes correct, sometimes not, i cannot see the logic behind it. However, I found that the quantities "Wall Irradiation Flux" and "Wall Absorbed Radiation Flux" are correct at myInlet. This is sufficient, as I can calculate the net "Wall Radiative Heat Transfer" as Irradiation - TextBlackBody*4 Sigma * Area. TextBlackBody is the "External Blackbody Temperature" BC set at Inlets/Outlets. Thanks again, Problem Solved PS my guess is that "Wall Radiative Heat Flux" is too derived as difference between other quantities, and that at some point, the local fluid temperature is used instead of the External BB Temperature, causing the non-sensical Output ...