When tasked with developing a heatsink that works in either horizontal or vertical orientation for a dc power subsystem for a commercial airliner, rather than developing an entirely new heatsink geometry, which would have taken a large amount of time using conventional build and test methods, Crane Aerospace & Electronics used Flomerics’ Flotherm thermal simulation software to help meet the performance requirements.
Typically, this type of system would use fin-type heatsinks on the exterior sidewalls of the enclosure; however, in this case the default design would work only in the horizontal or vertical orientation, but not both.
Crane mechanical engineer Mark Resler and other Crane engineers brainstormed and came up with six different alternative heatsink configurations, which included:
Plate and standoffs
45º angled fins
Short-flanged fins with outer flange
45º angled fins with outer flange.
The conventional approach to evaluating these concepts would be to build prototypes and test their performance, but that was found to be too expensive and time-consuming and would not have met the customer schedule. Thermal simulation with Flotherm made it possible for Resler to evaluate a wide range of designs quickly and at relatively low cost. Resler used the pattern generator in Flotherm to produce the fins.
“Flotherm quickly generates a model and makes it easy to change boundary conditions, environmental conditions, and gravitational direction,” Resler said. “I used these capabilities to model all six geometries at various altitudes and ambient temperatures.”
Simulations were conducted twice for each design, in the horizontal and vertical orientations. Simulation results showed that the plate and standoff design provided the best overall performance for both horizontal and vertical mounting. Resler then performed a trade study that involved simulating the performance of the plate and standoff design while varying the length of the standoff.
“Building and testing several different prototype configurations would have had a significant cost and schedule impact,” Resler said. “Thermal simulation allowed us to optimize the heatsink thermal performance and weight in a very short time period. Thermal simulation also enabled us to optimize the design to improve its performance to a level that would have been impossible to achieve with the build and test method within our schedule constraints.”