A sealed pouch containing water-based gel that absorbs heat through phase change (melting) to provide passive cooling for temperature-sensitive shipments without mechanical refrigeration. While gel packs offer simple, affordable cooling for short-duration chilled transport, they are fundamentally unsuitable for maintaining frozen temperatures in multi-stop delivery operations—a limitation that budget-focused competitors exploit at the expense of product quality.
How Gel Packs Work
Gel packs provide cooling through latent heat absorption:
- Water-based gel frozen solid before shipment (typically -20°C to -25°C)
- During transport, gel absorbs heat from surroundings
- Phase change (melting) at approximately 0°C absorbs significant energy
- Cooling continues until gel fully melted
- No active temperature recovery once thermal capacity exhausted
Gel Pack Performance Reality
| Condition | Cooling Duration | Temperature Maintenance |
|---|---|---|
| Ideal (insulated, minimal opening) | 24-48 hours | Chilled (2-8°C) |
| Typical (some handling) | 12-24 hours | Above 0°C |
| Multi-stop delivery | 4-8 hours | Inadequate |
| SA summer conditions | 3-6 hours | Rapid failure |
Gel packs maintain chilled temperatures (2-8°C), not frozen temperatures (-18°C). Once melted, they provide no further cooling—unlike mechanical refrigeration that actively removes heat continuously.
Why Gel Packs Fail for Frozen Delivery
Frozen food requires maintaining -18°C or below. Gel packs cannot achieve this because:
Phase Change Temperature
- Standard gel packs melt at ~0°C
- Specialized frozen gel packs melt at -21°C but provide limited capacity
- Neither maintains -18°C once melted
No Recovery Capability
- Gel packs absorb heat—they cannot remove it
- Each door opening introduces heat that depletes gel pack capacity
- Multi-stop routes (15-40 openings) rapidly exhaust passive cooling
- No mechanism to restore temperature after thermal intrusion
South African Heat Challenge
- 35-40°C ambient temperatures accelerate gel pack melting
- Urban heat island pavement radiation adds thermal load
- Delivery vehicle interior reaches 50-60°C when stationary
- Gel pack capacity exhausted within hours
The Budget Delivery Gamble
Some competitors offer “frozen” delivery using gel packs at R75-120 per delivery (versus professional mechanical refrigeration at R216-350). The economics:
What They Save:
- No TRU equipment cost
- No TRU maintenance
- No refrigeration fuel consumption
- Lower vehicle operating cost
What They Risk (Your Product):
- Temperature rises above -12°C within hours
- Recrystallization damage begins immediately
- Product quality compromised before delivery
- No temperature documentation proving cold chain failure
- Customer receives damaged product with no recourse
Appropriate Gel Pack Applications
Gel packs work acceptably for:
- Short-duration chilled transport (<4 hours, few stops)
- Last-mile supplement to mechanical refrigeration
- Emergency backup during brief TRU failures
- Non-critical temperature products (flowers, some produce)
Gel packs are inappropriate for:
- Frozen food delivery requiring -18°C
- Multi-stop routes with frequent door openings
- Extended duration (>4-6 hours in SA conditions)
- R638 compliance requiring documented temperature maintenance
Comparison: Gel Pack vs Mechanical Refrigeration
| Factor | Gel Pack | Mechanical TRU |
|---|---|---|
| Initial cost | Low | High |
| Operating cost | Per-use | Continuous |
| Temperature range | Chilled only | Frozen to chilled |
| Duration | Limited (hours) | Unlimited |
| Recovery capability | None | Full |
| Multi-stop suitability | Poor | Excellent |
| Documentation | None | Continuous logging |
| R638 compliance | Inadequate | Full |
Related Terms: Ice Pack, Eutectic Plate, Passive Cooling