# solids in contact??!!

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 June 4, 2007, 16:24 solids in contact??!! #1 donia Guest   Posts: n/a hi, what 's the difference between internal and interface boundaries? i'm working with different solids in contact!each one has a thermal conductivity!what should i impose as boundary for faces connecting solids? thanks!!

 June 4, 2007, 16:48 Re: solids in contact??!! #2 AJ Guest   Posts: n/a Hi, It is contact resistance if you want to pick-up/predict heat transfer from one solid to other.... When you don't specify anything its assumed perfect contact between these two solids... How are these two solids in contact in reality? Are these in contact due to some pressure applied by bolt etc... then you have to go into next level of modeling to incorporate the thermal contact resistance between solids which is complex phenomena and depends on many factors: surface roughness of two surfaces, thermal conductivity, hardness, pressure etc.... Read few articles on this topic if these are relevant for you: http://meweb.ecn.purdue.edu/~CTRC/re...ts/TCC/tcc.htm http://en.wikipedia.org/wiki/Thermal...ct_conductance Type thermal contact resistance and perform google search and you will find many many articles on this... There is one site which could help you a lot on contact thermal resistance is following: http://mhtlab.uwaterloo.ca/MHTLarchive.html Have fun... AJ

 June 5, 2007, 04:22 Re: solids in contact??!! #3 Donia Guest   Posts: n/a hi AJ, in deed i wonna study heat transfer between the solids but i can't find "contact resistance" in boundary conditions list!!!??? any way thanks for help and for the information!!

 June 6, 2007, 23:48 Re: solids in contact??!! #4 AJ Guest   Posts: n/a Here it goes for contact resistance in Fluent: You could define thickness of material and material which will offer the thermal resistance... Select the wall which is between the two solids in contact, compute the contact thermal resistance externally using different methods ( CMY, Cooper etc...) and convert this resistance/impedance into a material which could offer this resistance. Under the BCs for this wall --> thermal tab, it should be coupled thermal condition, set material to the effecive material property, set thickness to the required thickness ( calculate 1D resistance from the t/k like).... You should be able to solve contact resistance problem this way... Icepak (another software) which uses Fluent has better GUI where in you could use a plate in the contact region which will have the contact resistance properties.... Just try with a material with fictious k=0.1 W/m-K and keep changing this value and see if the temperature is changing, with some finite thickness... You could also specify planar conduction by enabling Shell conduction ON for this interface material... Hope this helps... ENjoy... AJ

 May 27, 2010, 12:41 #5 New Member   Join Date: May 2010 Posts: 3 Rep Power: 9 I am simulating a test setup where a thermal interface material is in contact between two aluminum blocks. So in other words the TIM is sandwiched between two Al blocks. I defined the four contacting surfaces(lower of first block, upper and lower of TIM, upper of second block) as interfaces in Gambit. The heat tranfer is taking place with the material properties (density, K and Cp) but it cannot be accurate since I do not have the heat coefficient value as an input. I do not understand how to input the heat coefficient h for an interface? Do I have to changes the interfaces to walls? Would the heat transfer take place then? Any help would be highly appreciated. Omar

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