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Can You Heat Me Now? Formal Design Review

Can You Heat Me Now? Formal Design Review. Brie Frame Sandra Gonzalez Angela Tong Chenny Zhu. Department of Materials Science • 3.082 • Advisor: Hao Wang • March 11, 2004. Outline of Presentation. Objective Overview of Components of Device Phase Change Materials and Data

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Can You Heat Me Now? Formal Design Review

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  1. Can You Heat Me Now?Formal Design Review Brie Frame Sandra Gonzalez Angela Tong Chenny Zhu Department of Materials Science • 3.082 • Advisor: Hao Wang • March 11, 2004

  2. Outline of Presentation • Objective • Overview of Components of Device • Phase Change Materials and Data • Melting Energy Calculations • Battery Selection • Power Calculations • Hybrid vs. Electrical Design • Proposed Circuit • Future Work • Proposed Schedule

  3. Objective • Design and fabricate a heat therapy device for lower back pain with a future use for transdermal drug delivery.

  4. Components of Device Battery High Insulating Layer Heating Core Outer Covering Body

  5. Average Body Dimensions Waist Circumference: 37.48” (men) 34.88” (women) 36.18” (average) Back Width (at shoulder): 15.75” Back Length: 15.77” Waist to Hip: 3.93” 42” 12” 6” 4” Heating element volume: 6x4x0.25” = 6in3 or 10x16x0.5cm = 80cm3

  6. Heating Core • Potential Materials • Tetradecanol • Ethylene Carbonate • 2,6-Di-tert-butylphenol (liquid at room temperature) • Cis-Cyclohexane-1,2-dicarboylic anydride (toxic) • Benzylideneacetone X X

  7. PCM: Temperature vs. Time

  8. Melting Energy • Equation: Energy (W*h) = (ρ*V*ΔHf) / (MW)

  9. Battery Selection

  10. Heat loss to environment q=-k dT/dx q=-0.0037*(16°C/0.005m) q=8.88W/m2 q*A = P = 8.88 * 0.016m2 P = 0.142W Heat loss to body q= -0.025*(6°C/0.001m) q=150W/m2 q*A = P = 150 * 0.016m2 P = 2.4W Total heat loss P = 0.142 + 2.4 = 2.542 W q=heat flux W/m2 k=thermal conductivity W/mK Solid Silicone Rubber = 0.0037 W/mK Cotton = 0.025 W/mK T=temperature Heat Pack = 41°C Environment = 25°C Body Surface Temperature = 35°C x=thickness = 0.005m A = area = 0.016m2 P = power (W) 0.16m 0.005m Power Estimation 0.10m

  11. Hybrid vs. Electrical • Power needed to keep temperature at 41°C in air = 2.56W • 4.43 Whr to melt 105.6g of Ethylene Carbonate (EC) • 1.73hrs to melt 105.6g (EC) • 15min for 10g Ethylene Carbonate to cool to 35°C • Assuming cooling rate is at steady state, would take ~150min (2.5hrs) for ethylene carbonate to cool to 35°C • 2.5hrs + 1.73hrs = 4.23 hrs for one cycle • Save 2.5hrs of electrical energy per cycle = 6.48Whr

  12. Electrical Lighter Constant Heat Uses more energy Hybrid More energy efficient-use electrical energy to both heat body and PCM Staggered Heating Hybrid vs. Electrical

  13. Switch • Programmable Thermostatic Switch – Analog Devices AD22105 • Control temperature by adding resistors • Small – about 5mmx5mmx2mm • Cheap ~ $1 - $3 per switch depending on how many bought

  14. Circuit

  15. Insulating Material Potential Materials • COHRlastic Solid Silicone Rubber • Thermally Conductive R10404 • Low Thermal Conductivity 0.0037W/mK • Very Thin • R10480 • Low Thermal Conductivity • Flexible

  16. Future Work • Differential Scanning Calorimetry • Properties of 2,6-Di-tert-butylphenol • Polymer Gel combined w/ PCM for comfort • Fire resistant wire coating • Finding resistance for thermal regulation switch

  17. Proposed Schedule

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