Heat is the main enemy of refrigerated trailers because it alters the transported refrigerated product.
Heat enters inside the reefer trailer through gaps in door openings, through cracked door seals, through trailer floors, or out of the ceiling.
How does a reefer trailer work to keep the heat outside the box?
3 main goals of a reefer trailer
The three main goals of a reefer trailer are:
- To remove increased heat.
- To keep the product temperatures stable.
- To control the humidity level inside the trailer.
To accomplish the above mentioned goals, the reefer trailer is designed with a refrigeration system attached in the outside front part of the trailer. Also, it requires regular reefer trailer maintenance.
Reefer trailer specific characteristics
- Trailer Refrigeration Unit (TRU): The TRU is a self-contained refrigeration unit that has its own diesel fuel supply from a tank located underneath the trailer. It also has a small diesel engine and a refrigerant compressor. This device cycles as necessary to maintain the preset temperature while monitoring the inside temperature of the trailer compartment(s).
- Insulated Container: Foam insulation is used to insulate the walls of reefer trailers, and the doors seal tightly to keep out air. This guarantees that the temperature stays the same for the duration of the journey.
- A Chute for Air: Reefer trailer air chutes are flexible air ducts that lay flat against the trailer ceiling.
They connect to the refrigeration unit and act as a ventilation system that evenly distributes the chilled air throughout the trailer.
- Reefers are not designed to cool down a product. They, rather, remove heat, control humidity, and maintain the temperature inside at a specific level, specified by the customer, during the entire transportation of the product.
- The reefer trailer is powered by a separate fuel source.
- The temperature inside the trailer is set by a thermostat.
- Inside the chilled area of the reefer trailer, the floor usually has channels to allow the air to flow underneath the goods.
These reefer trailer specific characteristics help the refrigeration system to maintain a steady and cool environment inside.
Reefers are equipped with a closed refrigeration system (TRU)
Reefers are equipped with a closed refrigeration system at the front of the trailer.
These systems are designed to remove the heat from the inside area of a reefer trailer and, as a result, to maintain the temperature of a product during transportation.
These refrigerating systems function through three main components:
- Evaporator coil.
- Compressor (a small engine that powers the compressor).
- The Condenser.
The above three components of the refrigerated system create air pressure to create air flow inside the reefer.
As the air from inside of the trailer passes over the evaporator coil, it removes heat and redistributes the now colder air back throughout the inside area of the trailer.
The typical occurrences are:
- Loads are often too warm when they are loaded.
- Drivers don’t shut their reefers off before opening doors, and debris often blocks airflow.
These occurrences often greatly increase the potential for temperature issues upon delivery.
What is cycle vs. continuous air in a refrigerated trailer?
There are two different ways to run the refrigeration unit — cycle or continuous.
Running the refrigeration unit in cycles reduces diesel consumption, but also creates more temperature variance.
Many products require continuous cooling. Ripening produce, for instance, generates heat, and requires a steady stream of cool air to maintain a consistent temperature.
Some frozen loads are less temperature sensitive and can withstand slight temperature variances — in these scenarios, cycling may be okay.
Understanding the commodity specifications is extremely important for carriers since they are responsible for the product from the moment it is loaded onto their trailer until it is unloaded.
How much fuel does a reefer trailer burn?
The amount of fuel your reefer trailer burns depends on many things.
Everything from ambient temperature, product temperature (when loaded), type of unit, and the condition of the trailer can affect the amount of fuel you burn. Since a reefer unit is on a closed loop system independent of the truck, driving habits don’t affect fuel efficiency. However, a poorly maintained reefer unit could increase your fuel consumption.
If everything is running close to normal, a reefer’s 50-gallon tank could last up to 4-5 days. Simple habits, such as maintaining your reefer trailer can pay big dividends year after year. See what is reefer fuel.
As a word of caution, you should refuel your tank whenever you reach the 1/4 tank level.