GLove

Kristin BrodieJeff Colton

Colin GalbraithBushra MakiyaTiffany 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? Source of heat

How will they be different? Lightweight Smart

Temperature Sensor/Switch Rechargeable Battery Reversible Exothermic Material

Heat Loss Model Cylindrical Hand Power Lost @ -10C relative to Power Lost @ 25C 2rLq = 2L(T1-T3)/R = 2.5W

R = Fabric Resistance + BL Resistance

Conduction

ConvectionGlove Layers

Overview

Battery Powered Chemical

Rechargeable Non-Rechargeable

Uses 2 ‘D’ batteries

Reversible Non-Reversible

Lasts 18 hoursOne time use

Battery Operated Glove

Wires

NiCr Alloys Stainless Steel

Mechanical Testing Electrical Resistivity Testing

Mechanical Testing DataNiCr NiCrFe FeCrNi

Diameter (mm) 0.41 0.38 0.404

Stress* (ksi) 120 74-130 ~95

Extension (in) 1.95 2.16 3.5

*Expected Stress

Stress vs Strainfor 3 wires

0

20000

40000

60000

80000

100000

120000

0 0.005 0.01 0.015 0.02 0.025

Strain

Str

ess

(lbs/

in)

NiCrFe FeCrNi NiCr

Electrical Resistivity Testing

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

Measured Resistances

0

0.02

0.04

0.06

0.08

0.1

Expected R Measured R R* R**

Condition

Res

ista

nce

(W

/cm

)

NiCr 80:20 NiCrFe 60:16:24 FeCrNi 70:19:11

Wire Insulators

Teflon PTFE Tubing

Property Units Value

Resistivity Wcm 1018

Tensile Strength

MPa 21-34

Tm C 327

Operating Temp

C 260

Water Absorption

<0.01%

Thermal Conductivity

W/mK

0.25

Teflon Tubing

Nextel Braids

Batteries

Amphr 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 3.74

Final Impedance 48.8 39.2 30.3

Field Testing

At what temperature is your hand comfortable?

Tested 10 subjects Placed in freezer Dressed in winter clothes Wore gloves with heating element 1.7W of power supplied Temp recorded when subject said their

hand was warm

Conclusion Thermal Switch should turn power off at

~32C

Test Tglove(C)

Tenvironment(C)

1 32.94 -18.39

2 32.44 -18.17

3 31.89 -18.50

4 33.94 -18.78

5 32.11 -18.44

6 33.33 -18.00

7 29.28 -17.72

8 33.17 -18.67

9 33.11 -18.17

10 32.72 -18.33

AVG 32.49 -18.32

My hand feels warm, stop recording

Temperature Sensor/Switch

Resistance/Current Testing

Bimetallic Polymer

Before Switch

After Switch

Expected Temp (C)

32

Actual Temp (C) 32 3

Voltage (V) 3.74

Resistance (W) 0 >106

Current (A) 0.43 0.0012

FabricBlends of Polyester/Cotton were tested

Thermal Testing Input Power = 1.73 W

100cm of wire 3.7V

Temperature inside and outside of glove measured

Power Generated From Glove: 2rLq=2L(T1-T3)/R = 1.73 W

L/R = 0.018 W/K

Power lost using 100P* under conditions previously modeled: 2.7 W

Required Power vs Temperature

1

1.2

1.4

1.6

1.8

2

2.2

240 250 260 270 280 290 300

Temperature (K)

20C 80P 100P 20P 80C 100P *

Phase Change Materials (PCM)

Octadecane

Tm = 27.2° C Tc = 16.5° C Hc = 283.5 J/g Hydrophobic

Polyethylene Glycol (PEG)

Tm = 26.6° C Tc = 9.8° C Hc = 151.0 J/g Extremely hydrophilic

PCM IncorporationPURPOSE: To prevent leakage from glove when PCM melts.

Ideal Process Microspheres to maximize surface area Polypropylene (PP) / High Density Polyethylene (PE)

Can be used to encapsulate microspheres Can be drawn into fibers

Extrusion of PEG/PP: phase separation

Complications Different thermal properties of PEG and PE Lack of Encapsulation Capabilities Lack of Extrusion Facilities

Microsphere FabricationSuccessfully produced both paraffin and octadecane

microspheres.

Complications Inefficiency of filtering process Large scale production

Final PCM Designs

Octadecane Ground particles embedded in base

material. Polydimethyl Siloxane (PDMS) Resin

Thermal conductivity = 0.002W/m*K

5g octadecane in 10ml (~7.5g) PDMS

PEG Melting attempts failed. Heat sealed in bags. Low Density Polyethylene

(LDPE) Thermal conductivity =

0.33W/m*K

7g of PEG in ~11g LDPE

-(CH2-CH2)-

Comparison of PCM Designs

Octadecane in PDMS PEG in PE

Potential Heat: 2.36 JActual Heat: 1.16 J

Efficiency: 49%

Potential Heat: 0.66 JActual Heat: 0.43 J

Efficiency: 65%

PCM Conclusions Octadecane is more efficient than PEG. Polyethylene is more efficient than PDMS.

Future Recommendations Encapsulate octadecane in polyethylene. Extrusion

Temperature Difference vs Timefor 3 Different Gloves

0.0

10.0

20.0

30.0

40.0

0 10 20 30 40 50 60

Time (min)

T

(C

)

PEG Octadecane Control

Assembly

Fabrication of GlovesInner LiningOuter Cover

Connect wires to temp. switch

Connect wires to battery

Encapsulation of PCMs

Sew wire into glove

Cost Analysis

Battery Powered Gloves

NiCr Wire $1.50

Teflon Tubing $17.00

Li Battery $20.00

Bimetallic Temp Switch

$4.00

Polyester $7.50

Labor $10.00

Production Cost $50.00

Market Price $100.00

PCM GlovesOctadecane $2.50

PDMS $5.00

Polyester $7.50

Labor $8.00

Production Cost $23.00

Market Price $46.00

Competitors: $40-$150

ResultsBattery Powered Chemical

Rechargeable

Uses Li batteryTemp Sensor

Non-Rechargeable

Use 2 ‘D’ batteries More Power

ReversibleOctadecane >

PEG

Cycle ~15min Multiple cycles

Non-Reversible

Cycle 18 hours One cycle

Better at lower temperatures Better at higher temperatures

Future Work

Improvements Encapsulation process Incorporation of PCM into glove Incorporation of thermally conductive material into PCM gloves Incorporation of wire into glove

Insulation Ease of access to recharge battery On/Off switch Application of Wire Insulation Field Test Prototype w/ People or Heat Model

In Freezer

Acknowledgements

Professor Ceder

Professor Irvine

Professor Powell

Professor Roylance

Toby Bashaw

Erin Lavik

Tim McClure

Joe Parse

Yin Lin Xie

Test Subjects

Other MIT Faculty and Students who we consulted