Customer Brief: Sechan

Sechan Electronics was tasked with developing a new digital fire control system for the Paladin self-propelled Howitzer. Soldiers count on the reliability of this unit and Sechan backed it with a protracted warranty, so the engineering team used Pro/ENGINEER and CFdesign to insure maximum reliability and performance.

The system required a single chassis to house three single board computers and associated hardware. Maintaining safe operating temperatures for all of the devices within the chassis was essential. Due to the sealed nature of the chassis and the shock mounting configuration, cooling of the chassis depended solely upon free convection and radiation from the exterior of the chassis. Heat from the internal electronic devices was transferred to the chassis essentially by conduction, fans where not an option.

Critical thermal management required an accurate prediction of the buoyancy-driven convective flow and radiation heat transfer. CFdesign supplied Jim Smith, lead mechanical engineer at Sechan, an efficient upfront simulation platform to systematically evaluate and interactively visualize conduction, convection, and radiation heat transfer modes simultaneously.

"I ran a number of simulations, starting with simplified geometry and more encompassing assumptions, and progressing to more detailed and realistic models," explained Smith. "For example, initially radiation was ignored and the Pro/E model was extensively de-featured. Gradually, the model became a more authentic representation of the actual hardware and environment."

Smith used the parametric relationship between CFdesign and his native Pro/ENGINEER assembly to evaluate several design alternatives. Additionally, simulations were conducted on the heat pipe assembly and components, and the single-board computer frames, to minimize the weight while maintaining an acceptable delta T and structural robustness. "The integration with Pro/E was excellent and essentially transparent. We were dealing with fairly complex geometries and assemblies without incident," stated Smith, adding that within CFdesign, "meshing was painless and predictable."

Smith says putting CFD upfront in the design process allowed Sechan to eliminate the costs associated with two rounds of prototypes and, more importantly, "we achieved our objective four months faster than if we had relied on traditional prototyping and testing methods." Another advantage of using CFdesign, according to Smith, is seeing the total product performance picture. "There's no way data from a collection of thermocouples could have given us the same level of knowledge and confidence about our design. Verification of the CFD simulation by testing in an environmental chamber demonstrated the accuracy of the model with close correlation of temperature data."