SEL Thermal Card Guide

The goal of this project is to develop a card guide design that can be applied in SEL equipment that has a net thermal resistance less than 1 ⁰C/Watt between an aluminum tray (.05"-.1" thick) and the chassis (.05"-.1" thick). This involves creating an instrumented test stand for measuring heat transfer across the card guide. Results should be reconciled against an analytical model to assure accuracy. The recommended solution should meet SEL standards for vibration.

Deliverables

 * Experimental test set-up that can accommodate different guide configurations
 * Experiment design and test results that demonstrate which guide configurations are most effective
 * Comprehensive project documentation for easy future reference by client
 * Proof of Concept guide design

SolidWorks Flow Simulation
To determine a suitable card guide deign our group used SOLIDWORKS to model heat transfer rates with Flow Simulation. This was then calibrated to match the experimental setup, so we could have a verified test apparatus once the guide was manufactured. The testing aparatus was then simplified to a two plate study, so we could control temperature boundary condition and solve for varying surface area, thickness, contact pressure, and material properties. All these factors were varied in parametric studies to determine the point where thermal conduction is optimal.

Experimental Setup
For our test setup we have created a scale version of the thermal card guide. This experiment would allow us to use thermocouples to measure temperature differences on the guide and determine the conductive power. To do so the resistance was calculated using R=L/kA, where R is resistance, L is length between two thermocouples, k is the thermal conductivity of the material, and A is the cross-sectional area of the tray. Once resistance is found we used Q =(T_1-T_2)/R, where Q is the conductive power, T is the temperature at a point, and R is the resistance calculated.

Experimental Results
After completing the experiments we were able to draw some conclusions from the data. However, these experiments still have some distance to cover as matching it to the SolidWorks Flow-Sim models have not been fully achieved. There was still 22% difference between the simulation and the actual experiment, but the simulation was conservative in estimating the resistance. With the pressure experiment there was only a 13% difference between the conductive resistances of the aluminum and brass, functionally the brass could replace the aluminum as material for the guide. That being said the brass would be much more expensive. Secondly in the pressure experiment, to reduce thermal contact resistance, pressure was found to be effective.

Final Design
For our final design we created a two piece card guide with one thermally conductive piece and another used to apply pressure to the tray when inserted. This will ensure better contact with the guide and decrease contact resistance, which was the biggest issue with our system. The Final Guide Design had intricate bends in the spring steel, so it couldn't be produced in the shop and its manufacturing required a 6 week lead time. As an alternative our group designed and 3D printed a PLA bracket to use as a proof of concept.