Elma uses Flotherm in ATCA platform design

Elma thermal engineers used Flotherm to automatically run a series of flow simulations while varying various dimensions and other parameters to achieve design goals such as maximising airflow over the boards.

Elma recently developed a 13U ATCA platform that dissipates 4200W in the 14 main slots plus another 1120W in a rear transition module (RTM).

The boards themselves are 8U tall, leaving only 5U for cooling, including the fans and intake and exhaust plenums.

Ram Rajan, thermal engineer for Elma Electronic, said: 'At Elma we are strong believers in thermal simulation and use it frequently to design the spacing for air intake and exhaust, types of fans and blowers, the plenum space above or below the fans, the placement of air filters and the use of baffles to optimise chassis thermal management.

'We use the Mentor Graphics Mechanical Analysis Division's Flotherm because it is more user friendly, provides superior reporting tools and our customers have greater confidence in its accuracy.' Rajan used Flotherm's automatic optimisation module to explore the entire design space.

The Flotherm optimisation module automatically generates a series of models with design parameters varying over a design space defined by the user and runs these models while monitoring product performance to identify the optimal design.

Rajan added: 'I started with the fan-to-air filter and air-filter-to-boards dimensions because they determine the airflow spread between the different boards.

'After I optimised them, I used the Flotherm Command Center to optimise the intake-plenum to exhaust-plenum ratio, which dictates the total airflow through the system.' Rajan specified a goal of reducing the chassis' static pressure while maintaining airflow level and distribution over the boards at acceptable levels.

He specified 10 runs; the Flotherm Command Center then created a designed experiment that uses these runs to efficiently explore the design space.

Rajan added: 'With a couple of designed experiments run overnight, I was able to optimise every key dimension in the chassis and meet the performance requirements for the box with a minimum of time and effort.' The system uses three individually removable fan trays with two 120mm 48V fans in each tray.

The result is that the Elma S ATCA Carrier-Grade 13U system offers unmatched thermal performance by delivering 40 CFM per slot in the front card cage to cool more than 200W per slot and 6 to 10 CFM over the RTMs.