Hand Warmers

Basics

• This page aims to go over the various forms of Hand Warmers, Existing Off The Shelf Options, and potential for OSE Improvements/Development

Disposable

• These are a bit wasteful
• Essentially Iron Powder and Charcoal/Some other materials to Moderate the Redox Reaction (Slow Hot Rust, rather than a Metal Fire etc)
• POTENTIALLY could be collected+reprocessed
• Also potentially could be made from or reprocessed with DRI as that process yields itself well to Powderization
• Alternative Chemistries would be interesting to pursue, but Disposable Devices (Short of Emergency/Expeditionary Use) don’t really fit OSE Specifications

Reusable

Rechargeable

Electric

• Essentially just a battery, resistive heating element, and control circuitry cleverly packaged together
• Main concern is Battery Life (long term, Charge/Discharge Cycles, ESPECIALLY thermal management)
• They do have the advantage of being easily recharged, and typically having long run times (10+ Hours)

Phase Change Materials

• Pretty Neat
• Also if clear they have a neat visual of the Supercooled solution recrystallizing
• Main downside is short runtime
• For better or for worse they are recharged via Boiling
  • If you currently have Electricity etc this is a bit of a pain vs Battery Rechargeable Units
  • If Camping or currently Without Electricity, it is neat as even a Pot over a Campfire could work as long as you have water
• Typically Sodium Acetate in a Solution of Water (also potentially a Dye Added)
  • Could Paraffin Wax either in a mixture, or in a “heat spreader” outer layer extend the release of the heat?

Fueled Versions

• Disadvantage over Rechargeable is that you have a Fuel Cost to consider, not just the (comparatively low) Cost of Electricity etc
• Also in Combustible Atmospheres / Some Locations they probably aren’t allowed either
  • Although if Intrinsically Safe Battery Electric Hand Warmers exist is the REAL question
• Can have long(er) runtime, no issues with Cold Weather Operation, etc

Solid Fuel

• Insulated Box you put smoldering charcoal “sticks” in

Liquid Fuel

• Zippo Style Catalytic Hand Warmers
• Run on Lighter Fluid tests on other materials would be neat

External Links

• A Video by the YouTube Channel “Technology Connections” Titled “Reusable handwarmers that get hot by freezing” ( ‘’’~18 Minute Watch’’’ )
  • It goes over both the Phase Change Reusable ones, and the Disposable Iron Based Ones