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G Love Prototype Presentation Kristin Brodie Jeff Colton Colin Galbraith Bushra Makiya

G Love Prototype Presentation Kristin Brodie Jeff Colton Colin Galbraith Bushra Makiya Tiffany Santos. Presentation Topics. Materials Selection Processing Testing Future Work. Materials Selection: Fabrics. Key Properties: Heat transfer coefficient, good

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G Love Prototype Presentation Kristin Brodie Jeff Colton Colin Galbraith Bushra Makiya

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  1. G Love Prototype Presentation Kristin Brodie Jeff Colton Colin Galbraith Bushra Makiya Tiffany Santos

  2. Presentation Topics • Materials Selection • Processing • Testing • Future Work

  3. Materials Selection: Fabrics Key Properties: Heat transfer coefficient, good breathability, lightweight, low cost, good durability. •100% polyester (fleece) • 80% polyester, 20% cotton • 20% polyester, 80% cotton • 100% cotton (flannel)- intended as inner lining Cotton ignites at 250C Polyester melts at 260 C

  4. Materials Selection: Heating Element Key Properties: High resistivity, mechanical strength, large elastic region.

  5. Materials Selection: Wire Coating Key Properties: High electrical resistivity, high thermal conductivity, high Tm, low water absorption, good ductility, good weather resistance. • Teflon (CF2) is the best candidate. • Polyethylene has too low Tm and may melt. • Braided tubing will allow water through. • Glass is not flexible enough. • Silicone rubber has low thermal conductivity. Teflon: Resistivity >1018 ohm*cm Tensile strength 21-34 MPa Tm 327 C Thermal conductivity 0.25 W/m*K H2O Absorption <0.01%

  6. Materials Selection: Battery Key Properties: Flat, flexible, rechargeable, high capacity, weight.

  7. Materials Selection: Temperature Sensor Key Properties: Fast reaction time, good temperature control, cost.

  8. Materials Selection: Phase Change Materials Key Properties: Tm near that of human body, high heat of crystallization, ease of processing.

  9. Materials Selection: PCM Base Materials Key Properties: Flexible, hydrophobic, easy to process, contains microspheres, thermal conductivity, high Tm. PDMS resin: • Used as the base material for octadecane. • Easy to process-when mixed with a cross-linker it sets into a flexible rubber overnight. Polypropylene: • Can be made into fibers or sheets. • PEG can be incorporated directly, rather than fabricating microspheres first. • Atactic polymer should be easy to process. • High solvent resistance.

  10. PCM Processing: Microsphere Fabrication • Microspheres increase surface area, releasing heat faster. • Small particles can be incorporated into the fabric easily. SEM image of octadecane microspheres. They appeared to have melted and recrystallized during fabrication.

  11. PCM Processing: Incorporation 1) Embed microspheres in a base material. • Octadecane microspheres were embedded in PDMS. • There was no difference in DSC results compared to a regular piece of PDMS resin. This could be due to the quality or quantity of the microspheres or to properties of the PDMS. 2) Incorporate PCM directly into base material (polypropylene) and form into flat sheets. 3) Coat fibers or fabric with the PCM.

  12. Testing • Heat transfer coefficient of fabric • Place heating element in gloves • Use thermistor to measure inside/outside temp. • Measured to be 1.1-1.5 W/m2K • Equilibrium time ~5 min • Next Step: • Repeat this experiment with gloves containing PCMs

  13. Thermal Testing • h = I*V/[A*(T1-T2)] = 3.6*0.55/(.04*DT) • As h goes up, less heat is lost (small DT) • Polyester has the highest value for h • Graph for values with 3.6V and 100cm of wire

  14. Power Requirement

  15. Future Work • Improve octadecane fabrication process, make more microspheres, test a larger piece of silicone rubber with more microspheres. • Test PEG as an alternative PCM, either by making microspheres or by directly incorporating it into a polypropylene sheet. • Continue heat transfer testing of gloves. Test gloves with PCMs incorporated. • Coat or insulate wires (Teflon tubing is in the mail). • Test and incorporate thermal switch (in the mail). • Connection of wires to battery. • Cost analysis. • Continue working on quantitative heat transfer analysis

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