G Love Kristin Brodie Jeff Colton Colin Galbraith

G Love Kristin Brodie Jeff Colton Colin Galbraith Bushra Makiya Tiffany Santos

Objective To create a glove that will generate heat to help keep one’s hand warm in a cold environment What will this require? n Source of heat How will they be different? n n Lightweight Smart n Temperature Sensor/Switch n Rechargeable Battery n Reversible Exothermic Material

Heat Loss Model n n n Cylindrical Hand Power Lost @ -10 C relative to Power Lost @ 25 C 2 r. Lq = 2 L(T 1 -T 3)/R = 2. 5 W n R = Fabric Resistance + BL Resistance Glove Layers Conduction Convection

Overview Battery Powered Rechargeable Non-Rechargeable §Uses 2 ‘D’ batteries Chemical Reversible Non-Reversible §Lasts 18 hours §One time use

Battery Operated Glove

Wires Ni. Cr Alloys Mechanical Testing Stainless Steel Electrical Resistivity Testing

Mechanical Testing Data Ni. Cr Diameter (mm) 0. 41 Stress* (ksi) 120 Extension (in) 1. 95 Ni. Cr. Fe Fe. Cr. Ni 0. 38 0. 404 74 -130 ~95 2. 16 3. 5 *Expected Stress

Electrical Resistivity Testing All wire diameters are ~40 mm *R for wire wrapped around a finger **R for wire after work-hardening

Wire Insulators Teflon Tubing Nextel Braids Teflon PTFE Tubing Property Units Value Resistivity cm 1018 Tensile Strength MPa 21 -34 Tm C 327 Operating Temp C 260 Water Absorption Thermal Conductivity <0. 01% W/m K 0. 25

Batteries n n Amp hr Size Durability Recharge ability Serial # 603672 141988 597980 Discharge Capacity (Ah) 0. 754 1. 364 1. 181 Discharge Power (Wh) 2. 82 5. 10 4. 42 Length (mm) 48. 9 88. 3 65. 5 Width (mm) 34. 8 54. 9 36. 2 Height (mm) 5. 30 3. 03 5. 50 Final OCV (V) 3. 76 3. 74 Final Impedance 48. 8 39. 2 30. 3

Field Testing My hand feels warm, stop recording At what temperature is your hand comfortable? Test 1 Tested 10 subjects 2 n Placed in freezer 3 n Dressed in winter clothes n Wore gloves with heating element 4 n 1. 7 W of power supplied 5 n Temp recorded when subject said their hand 6 was warm 7 Conclusion 8 n Thermal Switch should turn power off at 9 ~32 C 10 AVG Tglove(C) Tenvironment(C) 32. 94 -18. 39 32. 44 -18. 17 31. 89 -18. 50 33. 94 -18. 78 32. 11 -18. 44 33. 33 -18. 00 29. 28 -17. 72 33. 17 -18. 67 33. 11 -18. 17 32. 72 -18. 33 32. 49 -18. 32

Temperature Sensor/Switch Bimetallic Polymer Resistance/Current Testing Before Switch After Switch Expected Temp ( C) 32 32 3 Actual Temp ( C) Voltage (V) Resistance ( ) Current (A) 3. 74 0 >106 0. 43 0. 0012

Fabric Blends of Polyester/Cotton were tested Thermal Testing n n Input Power = 1. 73 W n 100 cm of wire n 3. 7 V Temperature inside and outside of glove measured Power Generated From Glove: 2 r. Lq=2 L(T 1 -T 3)/R = 1. 73 W L/R = 0. 018 W/K Power lost using 100 P* under conditions previously modeled: 2. 7 W

Phase Change Materials (PCM) Octadecane n n Tm = 27. 2° C Tc = 16. 5° C Hc = 283. 5 J/g Hydrophobic Polyethylene Glycol (PEG) n n Tm = 26. 6° C Tc = 9. 8° C Hc = 151. 0 J/g Extremely hydrophilic

PCM Incorporation PURPOSE: To prevent leakage from glove when PCM melts. Ideal Process n Microspheres to maximize surface area n Polypropylene (PP) / High Density Polyethylene (PE) n Can be used to encapsulate microspheres n Can be drawn into fibers n Extrusion of PEG/PP: phase separation Complications n Different thermal properties of PEG and PE n Lack of Encapsulation Capabilities n Lack of Extrusion Facilities

Microsphere Fabrication Successfully produced both paraffin and octadecane microspheres. Complications n Inefficiency of filtering process n Large scale production

Final PCM Designs Octadecane n Ground particles embedded in base material. n Polydimethyl Siloxane (PDMS) Resin n Thermal conductivity = 0. 002 W/m*K PEG n Melting attempts failed. n Heat sealed in bags. n Low Density Polyethylene (LDPE) n Thermal conductivity = 0. 33 W/m*K -(CH 2 -CH 2)- n 5 g octadecane in 10 ml (~7. 5 g) PDMS n 7 g of PEG in ~11 g LDPE

Comparison of PCM Designs Octadecane in PDMS PEG in PE Potential Heat: 2. 36 J Actual Heat: 1. 16 J Potential Heat: 0. 66 J Actual Heat: 0. 43 J Efficiency: 49% Efficiency: 65%

PCM Conclusions n n n Octadecane is more efficient than PEG. Polyethylene is more efficient than PDMS. Future Recommendations n Encapsulate octadecane in polyethylene. n Extrusion

Assembly Sew wire into glove Connect wires to temp. switch Encapsulation of PCMs Connect wires to battery Fabrication of Gloves Inner Lining Outer Cover

Cost Analysis PCM Gloves Battery Powered Gloves Ni. Cr Wire $1. 50 Octadecane $2. 50 Teflon Tubing $17. 00 PDMS $5. 00 Li Battery $20. 00 Polyester $7. 50 Labor $8. 00 Bimetallic Temp Switch $4. 00 Polyester $7. 50 Labor Production Cost Market Price $10. 00 $50. 00 $100. 00 Production Cost $23. 00 Market Price $46. 00 Competitors: $40 -$150

Results Battery Powered Rechargeable Non-Rechargeable Chemical Reversible Non-Reversible Octadecane > PEG Uses Li battery §Temp Sensor § Use 2 ‘D’ batteries § Cycle ~15 min § Multiple cycles § More Power § Better at lower temperatures § Cycle 18 hours § One cycle Better at higher temperatures

Future Work Improvements n n n n Encapsulation process Incorporation of PCM into glove Incorporation of thermally conductive material into PCM gloves Incorporation of wire into glove n Insulation Ease of access to recharge battery On/Off switch Application of Wire Insulation Field Test Prototype w/ People or Heat Model n In Freezer

Acknowledgements Professor Ceder Professor Irvine Professor Powell Professor Roylance Toby Bashaw Erin Lavik Tim Mc. Clure Joe Parse Yin Lin Xie Test Subjects Other MIT Faculty and Students who we consulted