Topic of the problem: Create smooth boundary conditions

mb_ing · May 10, 2012, 07:12

Hi everybody,
I want to simulate the free convection of a milling machine and its surrounding air. The machine itself is located in a hall modeled as a block around the machine (not visible in the pictures).
One aim is to get the Heat Transfer Coefficient of the machine surface.
Unfortunately, I just have the temperature of heating sources as boundary conditions on the surface (e.g.: Spindle). Therefore I have unrealistic local gradients between the regions with different temperatures and consequently problems with the HTC in these regions (see pictures). Additional information about the scene: HTC has a scaled color bar.
Does anybody know, how to create a smoother temperature distribution/boundary condition between the critical regions?
Thank you a lot in advance!

RobertB · May 10, 2012, 09:05

Model some or all of the metal as well. That is what physically conducts the heat away from the hotter parts.

mb_ing · May 11, 2012, 06:56

Hello everybody,
@RobertB: First of all thank you very much for your fast reply.
What do you mean by saying: “Model some or all of the metal as well.”?
Perhaps you matter about the “Holes” of the surface. But indeed they are caused by the scaled color bar.
The issue of my topic is to find a way how to create smooth boundary conditions. Maybe one possibility is to define tables for temperature with coordinates X, Y, Z.
Has anybody experience with this problem or knows how to handle this?
Thank you a lot in advance!

Ladnam · May 11, 2012, 14:58

I am not sure if I understand the problem. As long as you have set up the interfaces between the parts correctly with realistic resistances there should not be any unrealistic gradients. From the pictures it seems that this is not the case.

mb_ing · May 14, 2012, 05:45

Hi

@Ladnam: Thank you very much for your reply.
In this simply case only the free convection matters and the conduction won´t be considered. Because of this I have no interfaces.

In the front of the simulation a Boolean subtract was done. Actually, I get the surrounding air between the milling machine and the hall. So I just have a fluid and no interfaces have to be created.
I hope I could explain my problem and improve the hermeneutical difference

Thank you a lot in advance!

Ladnam · May 14, 2012, 15:50

I would have included conduction in the metal parts also.
Or else you can guess the temperature distribution and make a field function to create a non-uniform temperature on the boundaries.

May 10, 2012, 07:12	Topic of the problem: Create smooth boundary conditions	#1
mb_ing New Member MB_Ing Join Date: May 2012 Posts: 3 Rep Power: 14	Hi everybody, I want to simulate the free convection of a milling machine and its surrounding air. The machine itself is located in a hall modeled as a block around the machine (not visible in the pictures). One aim is to get the Heat Transfer Coefficient of the machine surface. Unfortunately, I just have the temperature of heating sources as boundary conditions on the surface (e.g.: Spindle). Therefore I have unrealistic local gradients between the regions with different temperatures and consequently problems with the HTC in these regions (see pictures). Additional information about the scene: HTC has a scaled color bar. Does anybody know, how to create a smoother temperature distribution/boundary condition between the critical regions? Thank you a lot in advance!

May 10, 2012, 09:05		#2
RobertB Senior Member Robert Join Date: Jun 2010 Posts: 117 Rep Power: 17	Model some or all of the metal as well. That is what physically conducts the heat away from the hotter parts. mb_ing likes this.

May 11, 2012, 06:56	Create smooth boundary conditions	#3
mb_ing New Member MB_Ing Join Date: May 2012 Posts: 3 Rep Power: 14	Hello everybody, @RobertB: First of all thank you very much for your fast reply. What do you mean by saying: “Model some or all of the metal as well.”? Perhaps you matter about the “Holes” of the surface. But indeed they are caused by the scaled color bar. The issue of my topic is to find a way how to create smooth boundary conditions. Maybe one possibility is to define tables for temperature with coordinates X, Y, Z. Has anybody experience with this problem or knows how to handle this? Thank you a lot in advance!

May 11, 2012, 14:58		#4
Ladnam Member Join Date: May 2010 Posts: 40 Rep Power: 16	I am not sure if I understand the problem. As long as you have set up the interfaces between the parts correctly with realistic resistances there should not be any unrealistic gradients. From the pictures it seems that this is not the case. mb_ing likes this.

May 14, 2012, 15:50		#6
Ladnam Member Join Date: May 2010 Posts: 40 Rep Power: 16	I would have included conduction in the metal parts also. Or else you can guess the temperature distribution and make a field function to create a non-uniform temperature on the boundaries. mb_ing likes this.

May 14, 2012, 05:45		#5
mb_ing New Member MB_Ing Join Date: May 2012 Posts: 3 Rep Power: 14	Hi @Ladnam: Thank you very much for your reply. In this simply case only the free convection matters and the conduction won´t be considered. Because of this I have no interfaces. In the front of the simulation a Boolean subtract was done. Actually, I get the surrounding air between the milling machine and the hall. So I just have a fluid and no interfaces have to be created. I hope I could explain my problem and improve the hermeneutical difference Thank you a lot in advance!

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