Today I'm going to dig into reefer trucks. We'll look at where they came from, what they are, what they're for, and why they mean so much to the logistics industry. I spent nearly five years handling operations for a company that exclusively ran reefer trucks. You'll find added elements of cost, upkeep, and maintenance that aren't present in many other forms of trucking. So, I'll be taking some time to dive into those things as we go.
Before anything else, let's discuss what reefers are.
What's a Reefer Truck?
"Reefer" is slang for refrigerated. The truck is your standard semi-cab. However, the reefer really is just the trailer. A "reefer truck," then, is a semi pulling a refrigerated trailer, designed to haul perishable goods. These trailers differ from cooling vans, which are just insulated and vented. What makes a reefer trailer different? Reefers include an active cooling system. Thus, you can transport frozen as well as refrigerated freight.
A reefer could also be temperature adjusted to haul heated goods as well. However, this is much less common.
You can find reefers using a couple of different cooling methods. You may see both diesel-powered generators and cryogenic cooling systems. Let's take a closer look at exactly how trailer cooling works.
How Reefer Units Work
Reefer units operate on a closed system. Removing heat and maintaining a steady temperature is what a refrigerated trailer system is all about. They operate by collecting and pumping heat throughout the system. Now I'll address the core components in making this work.
Components of Reefer Units and the Cooling Cycle
- The Compressor: There's a small engine within the reefer unit that drives the compressor. The compressor draws in gaseous refrigerant and, as you'd expect, compresses it. The pressure from this liquefies the gas. This then gives off heat to the body of the compressor and the air itself. From here, the temperature is still fairly warm, and the refrigerant goes through to the condenser.
- The Condenser: The condenser receives the liquid from the compressor. Then a heat exchange process begins. The warmth of the liquid flows to the walls of the tubing, then outside to the attached fins. The fins provide more surface area with which to cool outside air that comes in through the condenser fan. The process is very similar to how a radiator cools an engine.
- The Evaporator: The evaporator is inside the trailer. At this point, the refrigerant has given up most of its heat to the condenser and become a cool liquid. Then it goes into the evaporator through a metering valve. This valve controls the amount of cooling. Inside the evaporator, the now cool liquid refrigerant expands, turning back into a gas. It absorbs a great deal of heat from the surrounding finned coils during this process. The air from inside the trailer then blows over the evaporator. The air then goes back into the compressor, and the cycle begins all over again.
Next, I want to briefly touch on what parts make up the reefer trailer.
Parts of a Reefer Trailer
Reefer trailers naturally have more parts than standard shipping trailers. Here are the various pieces:
- Reefer unit (described above)
- Insulated box
- Air chute
- Air ride suspension
- Tire inflation systems
Most reefer trailers are 53 feet long, though they are available in other sizes as well.
Final Mechanical Tidbits
I just want to mention a couple more of the mechanical elements of the reefer trailer before moving on.
First, everything described above to make the reefer unit work properly requires fuel. This means a higher cost of operation for a driver or company. In addition to the typical fuel you'll need for the truck, you'll also need to keep the reefer fueled. Obviously, this means higher fuel costs.
Most reefer tanks hold around 50 gallons of fuel. This should last anywhere from four to five days, but that can vary.
Proper maintenance, ambient temperature, and overall condition of the trailer and unit can affect reefer fuel consumption. Since reefer fuel operates on a closed system cycle, how you drive doesn't affect its fuel consumption.
Finally, the temperature range on a reefer unit is remarkable. You can find units stretching from as low as negative 85 degrees Fahrenheit to as high as 104 degrees Fahrenheit.
Now, let's take a brief look at what people use reefers for.
Why Do People Use Reefer Trucks?
Reefer trucks are essential for the long-distance transport of perishable and temperature-sensitive goods. Frozen meats and fresh produce are the most common examples of these.
Companies use reefer units to maintain temperature. That means you can set a reefer unit to a specific temperature setting to maintain a product's temperature but not to actually change the temperature of the product. In the example of frozen meat, the required degree may vary.
For the sake of simplicity, let's suggest that a package of ground beef must be shipped and kept at 32 degrees Fahrenheit. The reefer trailer can maintain this temperature if the product has been loaded onto the trailer already frozen. You should not under any circumstances count on the trailer to take unfrozen meat and set your temperature below freezing in an effort to freeze the product. The reefer unit's cycle is not capable of this. The meat will spoil.
Let's take a look at where reefers came from.
A Short History of Reefers
As early as the mid-1800s, people and companies were trying desperately to find the most efficient way to transport perishable goods. For many years, trains were the only way to effectively transport this kind of freight. Yet companies desired an automobile alternative—something more portable that would be faster and cheaper.
Frederick McKinley Jones of Cincinnati, Ohio, was born in 1893 and served with the U.S. Army in World War I. After the war, he self-educated in many mechanical and electronic fields. Shortly after learning to build a transmitter for his hometown's radio station, he invented one of the most important devices in cinema history. His device finally allowed motion pictures to incorporate sound.
By 1938, Jones invented the first-ever portable air-cooling units for use on trucks. By 1940, he received a patent. He took on a business partner and built a multi-million-dollar company by 1949. That included the introduction of the first ever fully refrigerated truck.
Jones's invention of the portable cooling unit was pivotal during World War II. It enabled the transport of various perishable goods to military hospitals and tents across battlefields.
As you can see, the reefer truck has been a tremendous invention in world history.
The Greater Impact
Hopefully, by now it's clear how important reefers are to the industry of logistics. Absolutely imperative goods can only be hauled using reefer trucks. You'll find many branches to the tree of logistics. Reefer freight is among the most important.
It's also possible to use reefer trailers to haul dry freight. This allows for terrific versatility as a carrier. Dry freight runs can be key in getting your drivers to the higher paying reefer freight, particularly during the height of growing seasons.
That said, there's a higher degree of risk and responsibility that can come with reefer freight. Drivers must be extremely vigilant in ensuring the reefer unit is set to the right temperature. You must also be equally vigilant that the reefer unit is properly maintained. Should there be a failure that spoils the product, you may end up eating the cost of the entire load. As a fleet manager, you need to find and hire drivers who are diligent and trustworthy. If you want to retain those drivers while keeping costs low, it may help to use a fleet management system to keep things running smoothly and ensure drivers receive their pay on time.
All of these are important elements to consider when you're deciding whether to run reefer trucks.
This post was written by Matthew Zandstra. Matt has been working in transportation and logistics dispatch for the past six years, both as a broker and direct to drivers. He’s familiar with various facets of relationships, technical systems, pricing mechanics, and commodities.