09 Jun Thermal Modeling – Quick!
Medical devices often contain built-in heating and cooling elements; diagnostic devices must comply with assay thermal protocols and therapy devices must maintain biologics at optimum temperatures. Performing quick thermal finite element analyses (FEA) on device components early in the design process can help to optimize the design for thermal management, saving both money and time. Computer simulation modeling programs, such as the industry standard SolidWorks Simulation, will streamline FEA by allowing you to run a quick thermal analysis on the native solid model, revise the design and test it against real world scenarios. Supplementing and validating thermal analysis results using inputs gleaned from real-world experiments enables you to greatly improve the design and outcomes on subsequent iterations.
Start by eliminating as much complexity as you can from the component you wish to model. For example, you can delete areas of the component that are not thermally relevant or if the component is symmetrical, using SolidWorks you can strip away half of the model and run the study over just one half of the symmetric component. Runtime on studies can vary widely from a matter of seconds for a simple steady state analysis to several hours for a large transient or nonlinear model. Using simplified geometry initially allows the simulation to run more quickly, which can make a drastic difference on larger and more complex models.
Next, define properties of the materials used in your device. Material properties are specified on material data sheets, and standard values can also be found in Solidworks’ own database for commonly used materials. Every material, adhesive or coating needs to be considered, since each one will conduct, retain, insulate, lose or transfer heat differently.
Setting realistic inputs and boundary conditions is critical. What boundary conditions externally influence your model? Are there any external heat sources and how many watts of internal heat are generated? Is there external insulation? Do you have a convective boundary or is the part exposed to radiation? Using SolidWorks, you can quickly set these thermal boundary conditions as well as the locations and direction of any thermal loading conditions applied to the part. Then determine how much detail you’d like to see in your results, trading off the mesh resolution required with model run time.
Run the study and compare the computational results with experimental findings or those found in the literature. Do your results make sense? Dive down a little bit further, adjust a few values, and do some rough hand calculations to make sure everything seems reasonable. This is where unique engineering expertise always comes in handy – to help validate whether analysis results match physical testing. A good study will inform the direction of your design, and in turn your experimental findings will inform how you conduct future simulations. Calibrating your computer model against real-world results will go a long way to “reality check” your designs before you travel too far along the pathway of physical iterations.
Key Tech has run thousands of quick thermal models, usually with the goal of getting to an accurate prototype faster. We’ve developed an extensive library of parametric analyses for a variety of medical components, from robotic surgical tools to automated instruments and their disposable cartridges. The accumulation of these models and the knowledge gained from their interpretation speeds progress in two ways. Instead of starting over each time, we can modify models from our library. And our understanding of prior outcomes sometimes allows us to skip analysis iterations altogether, moving more quickly toward a final solution. Our goal is to take a study just as far as necessary and with the right amount of precision, to advance the best design for our clients in the shortest possible time.