Contact heat resistance

[Nexxon]

Hello,
I am currently working on the thermal assessment of a cubesat with ansys. I would like to implement in the model the contact heat resistance between the components of the satellite. Typical contacts are aluminium planes, bolted, with a surface roughness of ~Ra 3.2, and under vacuum conditions. Tests will follow to determine the precise value of the resistance, but this will be in a while and I need some (rough) estimation now. Anyone could help me? any references about this topic?
Thank you very much

 

[Dougt115]

I would convert the Ra number to a percent surface contact area. You could use radiant heating for the non- contact area if you like.

 

[racookpe1978]

Verify the torque being assumed for the bolted joint, and establish that specific torque requreid is actually being met on ALL of the parts as theya re wassembled. Surface finish is relatively easy to change by machining methods and polishing methods. Surface finish will be fairly consistent when run by today's CAd/CAM machines.

But a "nominal" or "loose" or "fully torqued" joint will allow the degree of contact to vary all over the place irregular. Some parts would be pass the heat exchange requirement, others will burn up. Higher bolt torques will also distort and bend poorly touching pieces into complete contact that would otherwise fail.

 

[FredRosse]

racookpe1978 (Nuclear) is very correct here, and controlling surface contact resistance to heat transfer is a daunting task. I have worked where normal fabrication work resulted in contact thermal resistances orders of magnitude greater than handbook listed values which were documented for lapped surfaces. Some engineers wanted to use the lapped values, but that is just not correct unless surfaces are actually lapped, and cleanliness is meticulous.