# Flow Simulation’s Thermal Analysis Capabilities – Part 1

For thermal heat transfer analysis, choose SOLIDWORKS Flow Simulation over the Thermal solver in Simulation Professional, Part 1 of 3 Conduction

With the exception of very few scenarios, when considering a thermal analysis solver for SOLIDWORKS, you should choose to use Flow Simulation, which is a computational fluid dynamics (CFD) code.  The most typical exceptions would be when: (1) there is no convective heat transfer mechanism in the problem that is being solved because likely the object(s) are in a vacuum and only transport heat through conduction and radiation; or (2) the thermal solution does not require a great deal of accuracy reflecting a physical test perhaps in the very early design stages when estimates are sufficient.  The main 3 reasons why Flow Simulation is the better option will be outlined in a series of three parts.

As noted above, there are three modes of heat transfer: conduction, convection and radiation.  I’ve made a long-form video explaining all of these modes in more detail, see link at the bottom, so I will only summarize them here in the series.

The solver in Simulation Professional should be thought of as the “Conduction heat transfer thermal solver,” though “Thermal” is used for short.

Conduction occurs in both fluids and solids through a temperature difference by electrons moving within the carrier material.  One can notice that the equation for solving the linear steady-state thermal conduction in matrix format, using the method employed by the Simulation Professional solver, fits the same exact pattern as that for Hooke’s Law used in linear structural stress analysis. So  for conduction can be solved in the same way as for elastic displacement.  One of the nice outcomes of this is that for Conduction, the unknown quantity solved for is the temperature {T} directly, which convenient that it is typically the quantity that we want to obtain.  [Unlike the unknown displacement {u} where subsequent calculations are done to get the strain and stress values that are wanted.] So in conclusion, the Simulation Professional Thermal solver is perfect suited for solving the conduction heat transfer problem, but convection and radiation can only be applied as known boundary conditions.  The question that I would want to consider in choosing Simulation Professional Thermal solver as my heat transfer analysis solution is whether solving conduction only is applicable in all cases.

We can say that for conduction only, Flow Simulation is at least equivalent to Simulation Professional’s capabilities.  There is an option to solve a problem for Heat Conduction in solids only, as shown in Image 1, so the flow equations are ignored and it only solves the energy equation.  Both Simulation Professional and Flow Simulation can be run as either steady-state or transient problems.

An example model of a regulator microchip was set up in both software packages running the heat conduction problem and convection applied as a boundary condition.  The results from both are shown in Image 2.  The results are nearly the same, where the main difference can be attributed to choosing different material properties from the available materials in each program; more specifically Flow Simulation has, out of the box, temperature-dependent properties for copper and solder.  You can also plainly see that there is a difference in the meshing schemes, but a further discussion on meshing will be handled in part 3.

If you are enjoying this series be sure to come back to read Part 2 and 3!

#### Joe Galliera

Senior Simulation Technical Manager , East area at DS SOLIDWORKS
Joe Galliera has been with SOLIDWORKS since 2002. Previously he worked in the aerospace industry primarily focusing on computational methods. He geeks out on computational fluid dynamics (CFD) and nonlinear analysis.