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.
==Problem Definition==
===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 
SEL Computer Model	Description
 	
This is the current SOLIDWORKS model of card guide and chassis. 
The preferred method of heat transfer is conduction as it doesn't use moving parts.
The electrical components generate heat in the card which is transferred to the tray. 
The tray then transfers heat to the chassis through the card guide.
===Specifications===
Sepcification 	Details
Thermal Performance 	Net thermal resistance of the guide must be ≤1°C/W between the tray it is supporting and the chassis it is fixed to.
Reliability 	Low DPU/Replaceable in case of failure.
Part Cost 	Card guide needs to cost less than $5.00/part.
Insertion Force 	Actual force of insertion.
Corrosion Resistance 	Must not promote galvanic corrosion.
Operational Simplicity	How easy it is to use.
Dimensions 	The card guide is to be 5in* long, 0.38in wide, and 0.50in tall. Design able to support variable length and variable tray thickness.
==Project Learning==
===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.
Test Setup	Description
 	
The testing apparatus was used to compare with our experimental model 
A heat source was placed on the end of the guide to create a mock resistor 
This model was the first assembly used to determine the thermal resistance through the card guide 
This model was the first assembly used to determine the thermal resistance through the card guide
It was found to have too many variables and too much variation from experimental model
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.
Two Plate Test	Description
 	
This design allows for an easy set-up and controlled variables. 
The temperatures are specified at each end of the plate assembly with goals specified throughout. 
This model allowed us to solve for contact resistance in the experimental setup. 
Parametric studies were able to be easily ran on this design with accurate results.
===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. 
Initial Setup	Thermocouple Figure	Description
 	 	
Two power resistors are being used as a heat source for the system 
The Bell Jar is a vacuum chamber will remove air from the system, thus reducing convection heat transfer 
There are several thermocouples placed on the system to measure the gradient across the plate and through the guide 
The measurements taken from this system can then be extrapolated for different sizes of card guides 
The recorded measurements can be used to compare with the SolidWorks and math models
Pressure Test Setup	Description
 	
Select masses were placed on the intersection of the two plates to create a pressure 
The pressure between the plates was varied to record and find differences in contact resistance ans pressure increases 
There are several thermocouples placed on the system to measure the gradient across the plate and through the guide 
The measurements taken from this system can then plotted and effective pressure can be determined 
The recorded measurements can be used to compare with the SolidWorks and math models
===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.
==Guide Designs==
===Initial Designs===
Guide Design 	Picture	Description
One-Piece Guide 	 	
One of the first guide designs created for pressure application 
Designed as one piece to create better conductivity and contact with chassis wall
Determined difficult to manufacture with extensive bends and spring fingers
End Capped Guide 	 	
Guide made with pressure application after insertion for easy of use
Base acts as heat sink to draw a large amount of heat
Determined to be too thick of base and difficult to manufacture with extruded base
End Latching Guide 	 	
Similar to the End Capped Guide, but differs with latching mechanism and plate thicknesses
Met specifications, but latch could only be oriented on one side, which would require left and right guides
Internal Pressure Guide	 	
One of the more intricate guides where plate could be inserted and then pressure applied
Similar to current guides on the market
Interior bends were found too expensive to manufacture and again had some problem with left and right application
===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.
Final Guide Design	Description
 	
The top piece is made of cartridge brass which has a thermal conductance of 121.2 W/m 
The bottom is made of spring steel, which can be stamped to have the spring fingers shown 
When the tray is inserted into the guide the spring finger will exert a pressure upwards to contact the top part of the guide 
This model was determined through simulation to have a thermal resistance of .8°C/W
This product wasn't able to be manufactured for expo so a 3D printed proof of concept was used
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. 
Proof of Concept Design	Description
 	
The PLA bracket has slightly flexible spring fingers that were able to apply similar pressure to the plate 
This part will act similar to the Final Design, but wont perform as well 
The guide was mounted using bolts with the cartridge brass top for proof of concept 
The design was ran in a comparative test where it performed slightly better than the existing guide
===Design Validation===
Parametric Model	Description
 	
Values found in the SolidWorks parametric study gave design parameters for surface area and thickness of the guide
In the parametric study the new guide design had a lower thermal resistance than desired 1°C/W
An experiment was ran with a heat source in the center of the plate and temperatures were measured at either side with a thermal camera 
The new guide had about a two degree temperature difference determined through thermal pictures in ambient conditions
==Team Information==
 
Team "CTB"	Team "CTB" 	Team "CTB" 	Team "CTB"	Team "CTB"	Team "CTB"
Member 	Biography 	Discipline 	 	 	
Marc Dobson
Team Orginizer	First generation college student, born and raised in Idaho. Anything outdoors is my game, but Netflix is also my friend. I choose to become an engineer to create a positive change in not only the world but my bank account as well. 	Mechanical Engineering	 	 	
Collin Mabe 
Treasurer	Born and raised in Boise Idaho I look forward to starting my career as an engineer in the near future. I enjoy fishing, hunting, hiking, and really anything that involves the outdoors. Using my skill set to help engineer a better world is the source of my drive, hopefully someday I will get to realize this dream.	Mechanical Engineering	 	 	
Nick Tobe
Primary Contact	Graduating senior at the University of Idaho from Eagle, Idaho. I plan to move to Auburn Hills, Michigan to pursue a mechanical engineering career in the automotive industry. I enjoy playing soccer and biking during the summer and in the winter I spend my free time snowboarding. 	Mechanical Engineering	 	 	
Michael Wendell
Secretary	I am from Eagle, Idaho and am Senior in Mechanical engineering at the University of Idaho. I plan to graduate and move to Boise and find a career in engineering. My interests include golfing, playing soccer, and riding my motorcycle. 	Mechanical Engineering