Definition: Reusable refrigerant pack containing water, gel, or phase-change material, frozen and used for passive cooling in insulated containers.
Types:
- **Water-based**: Freezes at 0°C, inexpensive, readily available
- **Gel-based**: Freezes at 0°C, remains pliable when frozen, easier to pack
- **Phase-change material**: Custom freezing point (-5°C to +15°C), precise temperature maintenance
Applications:
- Small parcel shipping (last-mile delivery)
- Pharmaceutical shipping (vaccines, biologics)
- Fresh seafood transport
- Backup cooling
Sizing: Typically 10-30% of total package weight should be gel packs for 24-hour protection
Limitations:
- Limited duration (12-48 hours typical)
- Requires freezing access
- Weight penalty (shipping cost impact)
- Not suitable for large volumes
Related Terms: Phase Change Material, Passive Cooling, Insulated Packaging