In one of my recent flow simulations I noticed something a little wonky with a definited contact resistance between two surfaces (K/W option). So I decided to make a basic flat-plate on flat-plate conduction-only model to test this out.

I applied a heat load to one surface of said plates & set the far surface to 25 deg C. Ran the model without any contact resistance & observed the expected temperature rise between the plates based off of hand calculations. I then added in a contact resistance of 0.01 K/W & with a heat load of 1000W I would expect to see a 10 deg C increase in my delta T. But instead I'm seeing a 40 deg C increase in delta T -- off by a factor of 4x.

To further verify what I observed, I ran the same model in a thermal FEA w/ a contact resistance, which output the correct/expected 10 deg c rise in delta T.

Finally, I went back to solidworks flow, separated my two plates by 0.010", & applied a thermal joint at this gap with a thermal resistance of 0.01 K/W. Results confirmed the expected 10 deg C delta T as well.

Is there something I'm missing about the way that the contact resistance works? Or is this a bug?

Thanks.