A working fluid that absorbs heat at low temperature (evaporator) and releases heat at high temperature (condenser) through phase changes between liquid and gas states, enabling the refrigeration cycle that maintains frozen and chilled temperatures. Refrigerant selection affects cooling capacity, energy efficiency, environmental impact, and regulatory compliance—making it a critical but often overlooked specification in transport refrigeration equipment.
How Refrigerants Work
The refrigeration cycle depends on refrigerant properties:
- Evaporation: Liquid refrigerant absorbs heat from cargo space, boiling into gas
- Compression: Compressor increases gas pressure and temperature
- Condensation: Hot gas releases heat to atmosphere, condensing to liquid
- Expansion: Liquid passes through expansion valve, dropping pressure and temperature
- Cycle repeats: Cold liquid returns to evaporator
Refrigerant thermodynamic properties—boiling point, latent heat, specific heat—determine system performance at different operating temperatures.
Common Transport Refrigeration Refrigerants
| Refrigerant | Type | GWP | ODP | Common Use | Status |
|---|---|---|---|---|---|
| R404A | HFC blend | 3,922 | 0 | Transport refrigeration, cold storage | Phase-down |
| R134a | HFC | 1,430 | 0 | Vehicle AC, some refrigeration | Phase-down |
| R290 (Propane) | Natural HC | 3 | 0 | New equipment, small charges | Growing |
| R717 (Ammonia) | Natural | 0 | 0 | Large industrial | Established |
| R744 (CO₂) | Natural | 1 | 0 | Emerging applications | Growing |
| R449A | HFO blend | 1,397 | 0 | R404A replacement | Current |
| R455A | HFO blend | 148 | 0 | Low-GWP alternative | Emerging |
GWP = Global Warming Potential (CO₂ = 1) ODP = Ozone Depletion Potential
Environmental Regulations
Refrigerant regulations are tightening globally:
Montreal Protocol / Kigali Amendment
- Phase-down of high-GWP HFCs
- 85% reduction in HFC consumption by 2047
- Affects equipment availability and service costs
EU F-Gas Regulation
- Prohibits GWP >150 refrigerants in many applications since 2022
- Drives transition to low-GWP alternatives
South African Context
- Following international phase-down schedules
- Equipment using R404A (GWP 3,922) faces service challenges
- Low-GWP alternatives increasingly available
Why Refrigerant Choice Matters
Refrigerant affects transport refrigeration performance:
Cooling Capacity
- Different refrigerants have different volumetric cooling capacities
- Equipment designed for specific refrigerant characteristics
- R404A has high capacity but high GWP
- R290 (propane) has excellent efficiency but flammability concerns
Energy Efficiency
- Natural refrigerants (R290, R717) typically have better COP
- R455A shows 4.3% better COP than R404A in studies
- Efficiency differences affect fuel consumption throughout equipment life
Service Availability
- High-GWP refrigerants facing supply restrictions
- Service costs increasing for legacy refrigerants
- Technician training for new refrigerants varies
Altitude Effects
- Refrigerant performance affected by ambient pressure
- Johannesburg altitude affects refrigeration cycle efficiency
- Equipment specification must account for operating conditions
The R404A Phase-Down Reality
Most existing transport refrigeration uses R404A:
- Proven performance in frozen transport
- Widely understood by technicians
- Abundant parts and service infrastructure
But R404A faces phase-down:
- GWP of 3,922 (nearly 4,000× CO₂ warming potential)
- Supply restrictions increasing costs
- New equipment increasingly uses alternatives
- Retrofit options available (R449A, R448A)
Operators should consider refrigerant trajectory when purchasing equipment—low-GWP refrigerants avoid future service cost escalation.
Related Terms: Compressor, Evaporator, Condenser
Related Article: R448A vs R404a: The Refrigerant Upgrade That Actually Makes Sense for Altitude (Unlike the European Solutions Nobody Asked For)