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Coolit sways marine power-panel designers

Courtesy of Textron Systems

At Textron's AAI Division in Hunt Valley, MD, unmanned boats for military and commercial applications are a specialty. Recently its electronics designers developed a common marine power panel for installation in a boat engine room. The six-sided panel could house any of several circuit configurations, some of which produced high heat loads. When the configurations were submitted for thermal analysis, the electronics group dictated that the circuits were fixed, and nothing, not even the thermal pads could be changed.

The need to accommodate multiple component layouts left the thermal engineer with only two possible vent locations. There was no room for a heat pipe, or a bigger heat sink. "The only option," he explains, "was to manage air flow as efficiently as possible in order to remove the maximum heat."

First, he verified that airflow direction would have no impact on cooling. Then he split the ducting into 2 paths, biasing flow to the area with the highest heat. Using Coolit, he identified the most effective wall location to deliver adequate airflow to the hot side, with enough leftover to handle the secondary path.

As the thermal analysis proceeded, the electronic circuits were still in a state of flux. There seemed to be new versions constantly coming in for analysis. "Many times I had to rebuild the whole model," explains the thermal engineer. "Fortunately, that proved pretty easy to do. With Coolit, I could start a new model from scratch, have it up and running, and deliver results in the same day."

"Sometimes Coolit surprises you," he observes. "You expect one thing to happen and another thing does. One surprise was that small changes in object orientation made a significant impact on cooling."

At some point during the process, the electronics designers learned that the thermal engineer assigned to their project was a first time Coolit user.

"They expressed their concerns to me," notes the thermal engineering manager, " because they couldn't understand how our thermal engineer could be getting valid answers so quickly, when they couldn't. Another group within their general organization had been using a different thermal package and spent weeks running thermal analyses. Often the problems ran overnight, and even then, they couldn't get conclusive answers."

"When thermal engineer and I showed them how quickly we could obtain a Coolit solution, they were amazed. Not only was Coolit at least five times faster than what they were using, our answers were conclusive and theirs weren't."

"I used Coolit ribbons," explains the thermal engineer, "so they could visualize the air flow, and velocity and temperature changes. That proved a definite eye opener."

Though component changes were considered a no-no, he went on to prove that a slight change in the thermal pads would greatly decrease the amount of cooling required. The presented evidence was so strong that the designers relented and changed the pads. "They wouldn't have changed their minds if I hadn't been able to prove it," he notes.

When the design was completed, the worst case scenario proved the predictions to be accurate; there was more than a 5 degree buffer between maximum operating temperature and design limits.

CUSV - common unmanned surface vehicle - uses modular architecture to accomodate multiple configurations and interchangeable payloads.
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