Simulation Saves Solectron 3 Months and $40,000 in Cooling Outdoor Antenna
Solectron saved a considerable amount of time and money in prototyping and testing expenses by using computer simulation to model the cooling design of an outdoor WiFi antenna. "We used Flomerics' FloTHERM cooling simulation software to optimize and validate the design from a cooling standpoint prior to building the first prototype," said Robert Raos, Mechanical Engineering Manager for Solectron. "The result was that the initial prototype met all of our customer's performance specifications, saving at least 3 months and $40,000 that would have otherwise been required to identify and correct problems in the initial design concept."
The WiFi wireless access point is designed to be mounted outside on a pole and provide wireless service to a large building such as a hotel. The unit generates an internal heat load of 200 W and solar heat loading of approximately the same value. The maximum allowable temperature in the electronics compartment is 66oC based on a maximum external ambient temperature of 46oC. Other constraints include a maximum weight of 12 pounds and a maximum cost of $120 for thermal management components.
Raos investigated four alternative cooling methods including thermo-electric cooling, a panel mounted air conditioner, phase-change materials heat storage, and an air-to-air heat exchanger. The air-to-air heat exchanger design that he selected uses internal fans to provide air circulation over internal fins and external fans to move ambient air over external fins. Heat transfer is by a combination of convection to and from the fins to the air and conduction between internal and external fins. The internal and ambient air do not mix.
"I selected FloTHERM to analyze cooling performance because it is designed from the ground up for modeling electronics cooling and provides many different options for reducing the time required to model electronics components," Raos said. For example, Raos entered design parameters of the printed circuit boards, heat sinks, and fans into Flomerics' FloTHERM.PACK web site to generate compact models of them. He then downloaded the models and inserted them into his system model, eliminating the need to create detailed geometry for these components. The compact model provides an accurate approximation of the thermal behavior of the components. When the system model was complete, Raos solved it, generating results that included the temperature and flow velocity and direction at every point within the enclosure.
The simulation of the initial design showed that temperatures in some areas of the enclosure and on the board itself were hotter than the maximum of 66oC. Raos modified the enclosure and heat sink geometry and reran the analysis several times until the design met all of the customer's requirements. When the design was built and tested, the first prototype met all of the customers' requirements. "Simulation helped us zero in very quickly on a design that did exactly our customer wanted it to do," Raos said.
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