A reefer container, short for refrigerated container, is an intermodal shipping box equipped with a built-in cooling unit. Freight forwarders use them to move perishable cargo across long distances while keeping the internal environment strictly controlled. For fresh food and sensitive medical supplies, the entire supply chain depends on these units working correctly. A single temperature drop can ruin months of work and cost thousands in lost revenue. This article dives into the core mechanics, features, suitable cargo and more.
Core Mechanics
Cooling Unit
The cooling unit operates by running refrigerant through its three key components – compressor, evaporator, and condenser.
- Compressor
- The refrigerant is compressed (hence the name compressor) into a high-pressure liquid.
- Evaporator
- The refrigerant molecules constantly absorb heat from the environment until it gains enough energy to break away from the liquid to transform into vapor. This evaporation process cools the enclosed area.
- Condenser
- The heated gas is cooled back into a liquid, ready to be recycled.
Temperature Management
The cold air is circulated from the bottom through a special grooved floor known as a T-Bar Floor. This ensures all areas within the container are evenly cooled. Drains are fitted to each corner of the container to discharge excess water. For frozen shipments, the drains are fully plugged.
All reefer containers have a red load line that marks the maximum height for cargo stowage. It is typically affixed to the top of the side walls. Cargo that exceeds the line will restrict air flow and subsequently affect the cooling efficiency.
NOTE: Reefer containers do NOT freeze or chill warm goods during transit. They are meant for maintaining the temperature at the desired level. Shippers should pre-cool their cargo to ensure cold chain integrity.
Power
The cooling unit of a reefer container do not run on their own power. Instead, they draw power from different sources depending on its location and mode of transport. During trucking, they draw power from the attached portable generator sets (gensets). At port, they plug into the terminal’s power supply. At sea, they typically plug into a ship’s electrical grid directly.
Further Reading: What is International Sea Freight, and How Does It Work?
Dimensions and Specifications
Shippers must match their cargo volume to three standard equipment sizes available in international freight:
- 20ft Reefer: Holds approximately 28 cubic meters of cargo.
- 40ft Reefer: Fits roughly 58 cubic meters.
- 40ft High Cube (HC) Reefer: Carries about 67 cubic meters, providing extra internal height for taller pallets.
Standard units keep internal temperatures steady anywhere between -30 and 30 degrees Celsius. However, some cargo needs much colder conditions. High-value frozen fish or specific biologics require highly specialized super freezers. These advanced units push temperatures down to -70°C to keep the product viable.
Advanced Climate Control
Some reefer containers can also provide advanced climate control to safeguard the transportation of sensitive goods.
Precision
Digital, AI-driven thermostats maintain temperatures within a fraction of a degree. This is crucial for delicate pharmaceuticals or produce.
Further Reading: How AI is Revolutionizing Freight Forwarding in the UK
Humidity
Moving perishables requires more than just cold air. Humidity management is also necessary to prevent the growth of mould and moisture damage.
Atmosphere
Reefers utilize Controlled Atmosphere (CA) technology to regulate air composition within the container. For example, as fruit sits, it naturally releases ethylene gas and ambient heat. By adjusting oxygen and carbon dioxide levels, CA systems artificially slow down the ripening process of fresh fruit.
Common Cargo Types
The volume of temperature-controlled freight moving through global ports is massive. For example, the Port of Antwerp-Bruges closed the 2025 calendar year by handling a record 1,170,394 TEU (Twenty-foot Equivalent Units) of refrigerated containers. Fresh produce accounted for approximately 90% of those specific imports.
This daily global capacity primarily supports three main cargo categories:
- Food and Beverage: Shippers move heavy quantities of fresh produce, meat, seafood, dairy, and fine wine.
- Pharmaceuticals and Healthcare: Vaccines, biologics, and clinical trial materials degrade instantly if temperature thresholds break.
- Industrial and Chemical: High-end cosmetics, aerospace components, and specific hazardous materials require strict environmental stability to remain safe and functional.
Further Reading: IMDG 2026 Compliance Updates
Conclusion
Moving perishables is a high-stakes operation. Shippers must match the right equipment size with exact pre-cooling procedures to prevent cargo spoilage and compliance failures.
If your business needs absolute certainty on these routes, SL Global Logistics provides dedicated cold-chain management. We handle complex, temperature-controlled freight daily, specifically across the UK-to-Southeast Asia (ASEAN) trade lanes. We are one of the UK’s most reliable international freight forwarders, offering door-to-door solutions with a focus on customer satisfaction. Whether it’s import, export, or global shipping, our experience working with a wide range of clients ensures your goods arrive in perfect condition. Contact us today for a quote and let us manage your international shipping adventure with expertise and care.