Can your product take the heat? It's a common question, especially if your product contains heat-producing electronics or is exposed to a wide temperature range in use, shipping or storage. One way to find out is to build it and test it. However, increasingly companies are using thermal simulation to find out early in the development, when the product can be easily redesigned.
If you have a 3D CAD model of your product, you have the starting point for thermal analysis. The next step is to analyze the model with Thermal Finite Element Analysis (FEA) software.
This is the point where it can get challenging. Which Thermal FEA software to use? Is your CAD geometry "clean"? What are your thermal loads and boundary conditions? How quickly can the analysis be done? Are the results high quality - meaning that the simulation closely matches physical test results? Who will be your thermal analyst? Can the thermal analyst recommend effective solutions?
Fortunately there are best practices that can help in each of these areas.
Dozens of Thermal FEA software packages are available. They range from open source free-ware to modules of very expensive multi-physics packages. On the low end, the packages have limitations on the model size they will handle and may not allow import of CAD geometry. On the high end, the packages can cost tens of thousands of dollars and take weeks of training and months of experience for a user to become productive. The best practice is to start with a mid-range Thermal FEA package that integrates seamlessly with your CAD package of choice. Many companies find that this is sufficient for their needs. Others eventually move up to a high end package when their needs for higher accuracy justify the investment.
3D-CAD models of products are typically developed over time as the design is refined, and may contain historical artifacts that can interfere with thermal analysis. Therefore, it’s important to “scrub” the model to make sure that the CAD geometry is “clean”. Are there unintended interferences between parts in an assembly that should be removed? Are components that are supposed to touch, actually touching? The best practice is to address these issues, and also consider simplifying or removing detailed features that are inconsequential from a thermal standpoint, to speed up analyses. In some cases, it may be more efficient to generate a new simplified 3D-CAD model than to eliminate artifacts one by one.
Do you know what thermal loads your product will see? Will they change over time? Sometimes these loads are specified in the product requirements. In other cases they must be developed based on anticipated environmental conditions and power draw of heat-producing components. The best practice is to make sure that all of the thermal loads are addressed from the beginning, because re-running analyses with updated loads can be time consuming.
What are the boundary conditions for each component in your product assembly? It could be perfect heat transfer (bonded), no heat transfer (perfect insulation) or in most real world situations, something in between. The best practice is to work with a thermal analyst who has the experience to research and establish the right boundary conditions to correctly model the real-world product.
Thermal analyses can be time consuming to set up and run – and a project typically requires multiple analyses. An experienced thermal analyst will use best practices to minimize the time. Initial analyses can use a coarser mesh and run faster to locate the trouble spots, then be followed up using more refined meshes for detailed exploration. Analyses can be set to run overnight as well as during the day. The sequence of analyses can be tailored to speed up the whole process, even utilizing tools such as Design of Experiments (DOE), just as in physical testing in the lab.
How closely do the results of your thermal analyses match the real world test results? The best practice is to conduct a coordinated strategy of thermal analysis and physical testing. The thermal analysis parameters can be updated so that the results are a close match to the physical test results. At the same time, with good Thermal FEA, the number of physical tests can be limited and targeted, by relying on the thermal analysis results.
Do you have an engineer on staff with a thermal background who is also a design engineer and well versed in CAD? Do you have the budget for Thermal FEA software and training? If so, you may wish to purchase Thermal FEA software and run analyses in-house. If you don’t have the appropriate engineer and/or software and training budget, or have a limited need for thermal analyses, you may wish to consider outside resources. There are Engineering Product Development firms with Thermal FEA software and thermal analysts on staff. Outside resources can be found through value-added CAD resellers, internet searches and word of mouth. The best practice is to start with an outside thermal analyst, and as the needs increase, consider bringing the work in house. Even with a full time in-house analyst, some companies still use outside resources to supplement during busy times or to help with more difficult problems.
Thermal analysts can model your product and point out the thermal issues. A top-notch thermal analyst is also a good design engineer and can make suggestions on how to resolve the thermal issues and any related structural issues, and improve the design. The best practice is to find and utilize top talent. This will enable a tightly integrated and iterative design-analyze-test loop that will reduce your product development cycle time and save you money overall.
The Design Factory, Inc. is a Product Development firm in Shrewsbury, MA. We use Solidworks Simulation Professional for Thermal FEA as well as Structural, Vibration and Motion analysis. We recently helped a client design an outdoor enclosure so that the internally produced heat would melt the snow off of critical areas. What thermal problems can we help you solve?