FloEFD reduces thermal prototypes needed on Terra

Azonix, a division of Crane Co, is a provider of highly engineered computers and displays designed for extremely harsh environments.

James Young, design engineer for Azonix, said: 'FloEFD computational fluid dynamics [CFD] software enables design engineers without a fluid-analysis background to perform thermal simulation.

'The result is that we got the design right the first time, only had to make one prototype and avoided expensive design changes that typically occur in the late stages of the development process,' he added.

The Terra is a new embedded computer designed for use in the transportation industry, which is claimed to be completely sealed from the elements and designed for use in very hot environments.

Young continued: 'As with most of our products, we were limited to conduction and natural convection cooling.

'This presents a difficult challenge for modern electronics equipment.

'We opened the Solidworks model in FloEFD and defined the heat dissipation sources, material properties and the ambient temperature outside the enclosure at the product's design limit of 60C..

'Then we defined the goals and performed a thermal simulation.

'The software analysed the CAD [computer-aided design] model, automatically identified fluid and solid regions and allowed the entire flow space to be defined and gridded without user interaction and without adding extra objects to the CAD model.

'The software took about five hours to generate simulation results.

'The results showed, as expected, that temperatures on the surfaces of key components exceeded the allowable limit of 90C,' he added.

The conduction path from the heat-dissipating components to the heat sink and heat-sink geometry were the primary design parameters that were available to improve thermal performance.

The cross section of the heat spreader was increased and changed from aluminium to copper.

Gap-type thermal interface material was inserted at the interfaces between the components and the heat spreader.

The thermal interface material was modelled as a contact resistance, reducing the number of cells, rather than conduction through material.

'These changes substantially reduced the surface temperatures on the dissipating components, but not enough to meet the thermal requirements,' said Young.

'Then we optimised the design of the heat sink,' he added.

After about six different iterations, in each case changing the spacing and height of the fins, the heat sink was optimised and the internal component temperatures were minimised.

Young continued: 'The changes to the heat sink reduced the surface temperatures below the maximum allowable levels.

'The result was that we were able to complete the thermal design prior to building the first prototype.

'When the prototype was built and tested, the measurements were within five per cent of the simulation predictions.

'As a result, this was the only thermal prototype that needed to be built.

'This is a good example of how the new generation of embedded CAD tools can save money and time by enabling design engineers to optimise the design from a thermal standpoint early in the design process,' he added.

The Mentor Graphics Corporation Mechanical Analysis Division was formerly known as Flomerics.