applying heat flux in case of shadow and wall

Shamoon Jamshed · January 24, 2022, 10:00

Dear CFD ppl,

I want to apply heat flux from a paper on wall that is common between solid and fluid zones. As you know, Fluent creates shadow wall in this case. The wall is considered coupled by the solver since the mesh was built in ANSYS MESHER from ANSYS workbench. Now it is not clear if the heat flux boundary condition will be applied under Thermal TAB in each of these walls (wall and shadow)? If I apply the flux, the heat does not transmit to the fluid and a localized high temperature is created which increases Temp to infinity. I mean >5k which ultimately diverges the solution. So please help me out in this regard.

Regards,

SJ

AlexanderZ · January 25, 2022, 00:55

heat source is applied as volumetric heat source (not heat flux)
you should define wall thickness and specify heat generation rate (W/m3)

Shamoon Jamshed · January 25, 2022, 12:49

volumetric cannot be applied since no info is available about it. I have only heat flux data with me. Now if the coupled wall is defined, how can I define a wall thickness?

LuckyTran · January 26, 2022, 05:45

Choosing temperature or heat flux for either the wall or shadow wall uncouples the interface. Then you specify the heat flux on both the walls (positive for one and negative for the other). If this diverges then you have another issue.

Shamoon Jamshed · January 26, 2022, 09:38

When I apply the heat flux, the coupled shadow BC also gets heat flux automatically applied. This does not let me specify negative heat flux on the shadow wall. This means that the interfacing still remains intact after applying heat flux.

LuckyTran · January 26, 2022, 11:34

It should break unless your case is so special that it is somehow bugged. See Thermal Conditions for Two-Sided Wallsl.

aun.ali · January 27, 2022, 04:05

Thanks for your reply Lucky but what do you think about how this simulation can be done as shown in fig 22. although the flux is applied at the interface ?. is it correct to take air and patch it with 0 pressure to model vacuum in this case. Air and tube interface is restricting to apply heat flux.

MOHS · October 18, 2022, 11:59

Quote:

Originally Posted by AlexanderZ

heat source is applied as volumetric heat source (not heat flux)
you should define wall thickness and specify heat generation rate (W/m3)

where i can find a volumetric heat source option, in case of wall and shadow wall both has to give flux (or volumetric heat source) or only wall has to give

January 24, 2022, 10:00	applying heat flux in case of shadow and wall	#1
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	Dear CFD ppl, I want to apply heat flux from a paper on wall that is common between solid and fluid zones. As you know, Fluent creates shadow wall in this case. The wall is considered coupled by the solver since the mesh was built in ANSYS MESHER from ANSYS workbench. Now it is not clear if the heat flux boundary condition will be applied under Thermal TAB in each of these walls (wall and shadow)? If I apply the flux, the heat does not transmit to the fluid and a localized high temperature is created which increases Temp to infinity. I mean >5k which ultimately diverges the solution. So please help me out in this regard. Regards, SJ

January 25, 2022, 00:55		#2
AlexanderZ Senior Member Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34	heat source is applied as volumetric heat source (not heat flux) you should define wall thickness and specify heat generation rate (W/m3) MOHS likes this. __________________ best regards ****************************** press LIKE if this message was helpful

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January 25, 2022, 12:49		#3
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	volumetric cannot be applied since no info is available about it. I have only heat flux data with me. Now if the coupled wall is defined, how can I define a wall thickness?

January 26, 2022, 05:45		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,748 Rep Power: 66	Choosing temperature or heat flux for either the wall or shadow wall uncouples the interface. Then you specify the heat flux on both the walls (positive for one and negative for the other). If this diverges then you have another issue.

January 26, 2022, 09:38		#5
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	When I apply the heat flux, the coupled shadow BC also gets heat flux automatically applied. This does not let me specify negative heat flux on the shadow wall. This means that the interfacing still remains intact after applying heat flux.

January 26, 2022, 11:34		#6
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,748 Rep Power: 66	It should break unless your case is so special that it is somehow bugged. See Thermal Conditions for Two-Sided Wallsl.