Thermal Conductivity Analysis of Air Force Issued Socks

1. Issued Footwear Analysis Braden Eagar Robert McClain 25 Mar 09 ME EN 340 - 2

2. Overview • Introduction • Functional Specifications • Measured Data • Results/Conclusions

3. Introduction • To fly, fight and win, airmen need footwear that is comfortable and functional in a variety of environments. • U.S. Air Force issues socks, but airmen are authorized to purchase socks at their own expense • Objective: Determine if proprietary (Gold Toe) sock material cools better than 100% cotton or wool issued socks in a hot environment

4. Functional Specifications • Issued Boots designed for: • Varied Temp Range • Varied Environments • Hot/Cold • Wet/Dry • Break-In Easy • Rigid, Ankle Support • Socks • Can be changed depending on the environment • Issued socks: 100% wool • Other varieties: 100% cotton, proprietary cotton-poly blend Ellsworth AFB, S.D. 15 deg F in June Ellsworth AFB, S.D. 90 deg F in June

5. Measured Data • We measured the amount of time the issue boots require to cool from a high temperature • Black boot temperatures were used to calculate the thermal conductivity (k) of the sock.

6. Results • Calculations • Air • RaD = 1029.38 • NuD = 3.13 • hair = 0.926 W/m2∙K • Sock • k = 0.014 W/m∙K • Noise: • Uncertain contact resistance • Uniform heating in oven to control temperature and reduce moisture Sock Leather Quiescent Air L = 0.003175 m L = 0.00158 m Ti Tsur T∞

7. Conclusions • Thermal conductivities compared • Wool: k = 0.07 W/m ∙ K • Cotton: k = 0.03 W/m ∙ K • Proprietary (Gold Toe): k = 0.014 W/m ∙ K • Proprietary sock • Insulates better • Longer time to heat up • Longer time to dissipate heat

8. Questions?