What Is a Reefer Trailer?

Wondering what a reefer trailer is?

Reefer trailers are an important type of trailers for the logistic industry.

Some of the most critical products are hauled using reefer trucks.

Some characteristics about this kind of trailer:

• require constant cleaning after every load.
• transport perishable products.
• The Red Cross relies on reefers to transport blood from its donors to the hospitals and clinics in need.

Today I'm going to dig into what is a reefer trailer. We'll look at its definition, how are they working, and why reefers mean so much to the logistics industry.

What does reefer mean in trucking?

In trucking, a reefer is a refrigerated semi-trailer that is hooked by a semi-truck to maintain refrigerated freight in their prime condition per arrival to the delivery. These are products that require temperature control during transit are fruits, meat, fish, seafood, vegetables, dairy, and also non-food products such as flowers and pharmaceuticals.

These units have insulated walls and refrigeration units attached to them. That prevents the spoiling of the transported products, which may occur due to heat, moisture, poor airflow, or low temperatures inside the trailer.

Currently, there are two types of refrigerated trailers. These are reefer containers and reefer trailers. 

Reefer containers are used to haul freight by the sea while reefer trailers are used to haul freight by ground. 

How does a reefer trailer work?

It's important to understand that the reefer's refrigeration system only maintains a set level of temperature but it doesn't increase or decrease the temperature level inside it.

Because of that, the cargo has to be brought to the desired temperature level before being loaded in the reefer.

Reefers maintain the temperature and the humidity inside the trailer during the whole transit time. This entire refrigeration cycle is done by manipulating the inside air .

To create the ideal environmental conditions for the transported products, reefers have multiple sections such as:

• The control unit section:

The control unit allows you to set and adjust the internal atmosphere in the reefer such as the temperature, the alarm conditions, and in some cases ventilation and humidity levels.

• The interior fans section:

Interior fans located inside the reefer help to circulate the air to promote adequate temperature control and stability. 

With the help of an air chute attached to the trailer's ceiling, the airflow is blown to the back of the trailer and, from there, it circulates under the palletized freight. In this way, the flow of cold air inside the trailer is taken care off.  

• The fresh air vent section:

The fresh air vent allows the air from the outside of the trailer to enter and remove any gases from in the container, such as fruit-ripening ethylene gas.

• The evaporator section:

Excess moisture in a reefer can damage products, quicken food spoilage, and break down packaging, leaving contents vulnerable.

The unit evaporator helps to maintain the moisture inside the container. The reefer unit evaporator can either heat or cool the air that circulates past it from the fan.

• The condenser section:

Condensers may have air or water cooling.

The reefer is powered by a separate fuel source.

Drivers need to ensure there’s enough fuel in the tank, especially on long journeys. Typically, a full tank will last a few days, depending on the difference between the temperature of the load and the outside temperature.

The floor of the refrigerated container has a “T-floor” to allow for airflow under the cargo. Cold air blows from the refrigeration unit through the vents at the bottom of the reefer and to the back doors. The warm air at the top of the container flows back to the refrigeration unit over the cargo, where it chills for return to the interior.

This effect prevents the chimney effect from under the products. 

Consider these rules as well:  

• The cargo must be stable on the floor so that it doesn’t shift during transportation.
• The unit must always be set at the proper carrying temperature.
• All reefer trailers are built to maintain a temperature between -13 degrees F (-25° C) and 77 degrees F (+25°) C for chilled and frozen cargo.

However, there are specialized reefers that can go as low as -85 degrees F (- 65°C). These types of refrigerated trailers are used to transport items in the medical and chemical industries.

• Dehumidification controls must be checked.

A reefer unit has a dehumidification function that lowers the level of moisture in the air.

If pre-cooling is required, it must be the cargo that is pre-cooled and not the container, unless the container is loaded in an airlocked cold tunnel in the cold storage

• Ventilation setting is of utmost importance and must be set at the correct level.

As air will follow the path of least resistance, there should not be any restrictions for airflow. Also, there shouldn't be any gaps between the pallets and the floor. The doors must be closed using cardboard or even wood. This will then force the air to circulate correctly and reduce the potential for heat sinks (warm air continuously circulating) near the doors.

Generally, reefers operate by collecting and pumping out heat to maintain a steady temperature in the closed system of the unit.

Are refrigerated trailer airtight?

Refrigerated trailers are built with insulated walls made of steel, plastic, or some other non-porous material, and sealed very well to prevent heat from entering them, and keep the cool air inside where it belongs.

What are the dimensions of a reefer trailer?

A reefer's inside total cargo space is lesser than the exterior due to the refrigeration equipment taking up some of the room inside the container.

How do you set the temperature on a reefer trailer?

Temperature controls are the most important part of a reefer trailer. Without this function, the reefer would be unable to maintain a safe temperature for the transported products. And that could result in costly waste or even in dangerous reactions happening inside the trailer.

You can set the temperature and other critical settings for your reefer by using the control unit located on the outside of the container.

The basic steps are as follows:

1. Make sure that the reefer trailer receives from the power cord.
2. Turn the reefer unit on and wait for the unit to finish its start-up functions and self-tests. If the reefer displays an error message, do not continue using it or storing products inside.
3. Using the marked buttons, set the temperature for the inside of your reefer unit and confirm when you are finished.

To determine the correct temperature for your items, consider the following:

• The type of item you are transporting and the temperature it requires to arrive at its destination safely.
• The traveling distance and conditions along the shipment route.
• Whether you need a continuous set temperature or a cycled defrost temperature.
• Specific client, a company of regulatory requirements, or quality standards.

What do refrigerated trailers run on?

To make everything described above work properly, the reefer unit requires fuel.

In addition to the typical fuel you need for the truck, you also need the reefer fuel. Read more about what is reefer fuel.

This means a higher fuel cost of operation for the driver or the company.

Most reefer tanks hold around 50 gallons of fuel. This should last anywhere from four to five days. But that can vary depending on the proper maintenance, ambient temperature, and overall condition of the trailer.

Or you can decrease the fuel consumption of your reefer using an electric reefer trailer. 

Related:

Reefer trailer guide

How to Load a 53 Feet Reefer Trailer?