transient heat transfer coorelation

[casipancmonster]

I have a fairly simple model that when I run a steady state version provides results that are similar to what we see in the real world. However if I try to simulate the heat up process with a transient model it fails to correlate by orders of magnitude. I expect some variation given the uncertainty of the boundary conditions but it should be remotely close and I am having trouble identifying the source of the error.

I am working in mm N s mm which gives me a a thermal conductivity in the range of 200 for aluminum (mW/mm*K). Does this seem correct? I am unsure on my convection coefficients (forced convection around 0,1 (mW/mm^2 * K) but I do not think that is issue here as even if I turn off convection the parts still heat much more slowly than expected. I do not have radiation active.

I have considerable experience with mechanical structural analysis but much less when it comes to thermal.

thanks

L

 

[Dave442]

@casipancmonster: If you are getting correct values but you're just out by orders of magnitude is it possible that your units are not consistent? Might be worth checking your unit system against some of the guides that are available online, for example:

http://www.idac.co.uk/services/downloads/consistent.pdf

http://www.altairuniversity.com/wp-content/uploads/2012/04/Student_Guide_55-57.pdf

http://www.endurasim.com.au/wp-content/uploads/2015/02/EnDuraSim-Engineering-Units.pdf

 

[casipancmonster]

Thanks Dave, it is good to get some more sources to check my more obscure units but as far as I can tell what I am using is consistent. I will figure it out at some point.