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Film coefficient as a function of temperature
 
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atanu.das
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Joined: 20 Feb 2013
Posts: 9

PostPosted: Tue Oct 08, 2013 9:09 pm  Reply with quote

Dear expert,

I am doing a transient thermal analysis. How can I define a heat transfert coefficient(or film coefficient) as a function of the temperature (not as a constant value of temperature) on selected set of elements. I need temperature to calculate h for each load step on set of elements.

Film coefficient: h= 24.1*e-6*(T^1.63)

Thanks,
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Atanu Das

Indian Institute of Technology, Bombay
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ayo.brimmo
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Joined: 01 Jul 2013
Posts: 38
Location: Masdar City, Abu Dhabi

PostPosted: Wed Oct 09, 2013 2:03 am  Reply with quote

I think you might want to estimate the heat transfer coefficient over the expected temperature range of the elements, tabulate the solution then input directly.

So lets say you expect the temperature of the elements to fall between 0-500C, you manually calculate the values of H at 100,200,300,400 and 500C. If you are using workbench, inputting the resulting data as a boundary condition is pretty straight forward.
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Ayo Brimmo
Research Engineer
Masdar Institute of Science and Technology
UAE.
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mike.yaksh
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Joined: 05 Feb 2009
Posts: 291

PostPosted: Wed Oct 09, 2013 5:57 am  Reply with quote

Atanu

Usually the film coefficient is dependent on the difference of the surface temperature and the ambient. You need to input the an HF material temperature property using MPTEMP and MPDATA,HF,materialnumber
The HF is associated with the surface using the SF or similar command. Look at the element type and the keyopt will give you a choice of which temperature you want to use in the selection of the HF you defined during the solution. The one shown below is for the 2D thermal element

KEYOPT(1)
How to evaluate film coefficient:

0 --
Evaluate film coefficient (if any) at average film temperature, (TS + TB)/2

1 --
Evaluate at element surface temperature, TS

2 --
Evaluate at fluid bulk temperature, TB

3 --
Evaluate at differential temperature, |TS - TB|


Mike Yaksh
NAC International
Norcross GA

-----Original Message-----
From: xansys-bounces@xansys.org [mailto:xansys-bounces@xansys.org] On Behalf Of atanu.das
Sent: Wednesday, October 09, 2013 12:10 AM
To: xansys@xansys.org
Subject: [Xansys] Film coefficient as a function of temperature

Dear expert,

I am doing a transient thermal analysis. How can I define a heat transfert coefficient(or film coefficient) as a function of the temperature (not as a constant value of temperature) on selected set of elements. I need temperature to calculate h for each load step on set of elements.

Film coefficient: h= 24.1*e-6*(T^1.63)

Thanks,

------------------------
Atanu Das

Indian Institute of Technology, Bombay






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atanu.das
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Joined: 20 Feb 2013
Posts: 9

PostPosted: Wed Oct 09, 2013 11:40 am  Reply with quote

Thank you Mike for your reply.
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Atanu Das

Indian Institute of Technology, Bombay
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