CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Inteface thermal conductivity

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   March 10, 2002, 06:28
Default Inteface thermal conductivity
Posts: n/a
Dear friends,

My question is related to the inteface thermal conductivity between two adjacent materials. One is chip and the other is glass covering the chip completly. Within the chip there is a constant heat generation and in the glass no heat generation. The conduction model is supposed 2D (cylindrical coordinates) question is how can we determine the 2 effective thermal conductivities at the intefaces in radial and axial directions ???? As an example in Pakankar it is given as


where Kint,K1 and K2 are the thermal conductivities at the interface, the material 1 (chip for example) and material2 (glass for example)..but in presence of heat generation or heat source the interface thermal conducitivities ( radial and axial directions) should be different from this relation isn't it???

Waiting for you answers and helps



  Reply With Quote

Old   March 10, 2002, 22:53
Default Re: Inteface thermal conductivity
Posts: n/a
A good point. Yes, you are right - you can't use that type of formulation. Just make a cv energy balance.
  Reply With Quote

Old   March 11, 2002, 03:16
Default Re: Inteface thermal conductivity
Posts: n/a
Don't bother with that and use two independent control volumes at the interface, perform a heat flux balance through the interface and use the additional requirement that the control volume temperatures be equal. That way there is no need to blend the conductivities.

  Reply With Quote

Old   March 11, 2002, 04:15
Default Re: Inteface thermal conductivity
Henry Eatsink
Posts: n/a
Use FLOTHERM and it's ability to define explicitly an interfacial resistance in terms of K m^2/W.
  Reply With Quote

Old   March 11, 2002, 20:46
Default Re: Inteface thermal conductivity
Sebastien Perron
Posts: n/a
I assume you are using an FVM method.

This is another way of computing the interface conductivity. The formula you wrote was only valid for a constant mesh spacing.

This procedure is good for any coordinate system, only change the expressions for the numerical flux according to the flux in your coordinate system if different:

1) First you assume that the flux on either side of the interface is equal (conservativity of the flux):

K1 (T1-T)/D1 = - K2 (T2-T)/D2 (1)

2) express T (the temperature at the volume interface) in function of the others:

T = [ (K2/D2)*T2 + (K1/D1)*T1 ] / [ K2/D2 + K1/D1 ]

3) replace the expression for T in either side of equation (1) and make it equal to the flux across the interface:

K12 (T2-T1)/(d1+d2)

where K12 is the conductivity your looking for, after some manipualtion you get the final expression for it:

K12 = (d1+d2)K1K2/(d1K2+d2K1)

Good luck.
  Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Constant velocity of the material Sas CFX 15 July 13, 2010 08:56
Simulation of a single bubble with a VOF-method Suzzn CFX 18 October 2, 2009 04:18
mass flow in is not equal to mass flow out saii CFX 2 September 18, 2009 08:07
Porous Media Effective Thermal Conductivity Greg Perkins FLUENT 3 August 5, 2001 21:53
Info: Short Course On Thermal Design of Electronic Equipment Arnold Free Main CFD Forum 0 August 10, 1999 10:18

All times are GMT -4. The time now is 15:40.