# SW 2011 2D Thermal Simulation Heat Flow Units

Question asked by Ryan Thompson on Apr 20, 2016

Hello,

I am currently using 2011 to run a 2D thermal simulation on the cross-section of an aluminum window frame. I've cut out a section of my overall window to a thickness of 100mm, and have also filled in all internal cavities with solids, which are being assigned air as a material. The simulation is setup as a 2D simplification, with a section thickness of .001". As far as boundary conditions go, I have convection on the inside and outside edges with a 20 degree temperature difference, respectively. The simulation meshes and runs perfectly, and the temperature gradient seems very reasonable. My end goal is to calculate the window frame's U-value, and to find this value I need to find the heat flow through the frame. To do so, I am creating a resultant heat flow thermal plot, and I am probing all of the outer edges of my model on the cold side. This probe ultimately leads to a value for the average heat flux in units W/m^2. This would make perfect sense if I was running a 3D simulation, where area would be playing a role, however given this is a 2D simulation, it doesn't really make sense as to why it is presenting the heat flow as a function of surface area. I figured it was perhaps taking into account my model's thickness (100mm), so I made a new version that is 200mm tall and reran it, only to receive identical results for heat flow. I know it isn't taking into account my section thickness, since multiplying through by .001" gives very unreasonable results for the heat flux, so my question is how does SW calculate heat flux for 2D simulations? What is it using as a secondary term for the surface area? I need heat flux in W/m, so I need to know what to multiply my results by in order to remove the m^2 term.

Any help would be appreciated.

Thanks,

Ryan