Addressing Challenges in Reefer Trailer Temperature Monitoring

One of the most common questions customers ask cold chain experts is why the temperature inside a reefer truck or warehouse differs from the temperature reported by real-time temperature monitors. This is a critical consideration for products that are more sensitive to temperature fluctuations, such as vaccines.

This temperature difference is usually a matter of insufficient refrigerated airflow. To protect product shipments and ensure the cold chain remains unbroken, it is essential to understand why these temperature differences occur and how to prevent them.

What is Reefer Temperature Monitoring?

Reefer temperature monitoring (sometimes referred to as refrigerated temperature monitoring) is a logistics process that uses tools to track the temperature of products in transit. This helps notify organizations of any temperature fluctuations that could affect product quality or shelf life.

Why is Temperature Monitoring Important for Reefer Trucks?

Products in reefer trucks need to be maintained at optimal temperatures during transit. If a temperature fluctuation occurs (i.e., the product moves outside its optimal temperature range), product quality can be compromised. If this condition persists for too long, the product may spoil, or even make unsuspecting customers ill.

This is especially evident in life science products, such as vaccines, which are particularly sensitive to temperature fluctuations and may become ineffective when exposed to them. For temperature-sensitive products, organizations have a responsibility to maintain the cold chain and protect customers from disease.

How Truck Refrigeration Airflow Works

Trailer refrigeration units are designed to circulate a blanket of cold air around the cargo. Cold air is blown in from the refrigeration unit located at the front top of the trailer. The air flows around the cargo, and depending on the packaging and trailer loading pattern, it may also flow through the cargo.

As the cold air passes through the trailer interior, heat entering the trailer from the outside is absorbed by the trailer surfaces and the products. The air returns along the floor to the refrigeration unit. Finally, the refrigeration unit expels the heat absorbed from the circulating air to the outside, and the process begins again.

How Poor Reefer Airflow Creates Hot Spots

Obstructed airflow can lead to warm zones inside the trailer. Typically, the door at the rear of the trailer is a warm spot because it is farthest from the refrigeration unit.

The exact location of hot spots can vary due to several factors, including the nature of the airflow obstruction, pallet loading patterns, trailer condition, the trailer's position relative to the sun, and more.

External factors are not the only cause of hot spots. Improper loading patterns can disrupt airflow within the reefer unit or cause products to conduct heat from other sources. There should be gaps between pallets and the trailer walls to allow air to circulate. Pallets should also not be stacked too high inside the trailer, as cold air is blown from the top of the trailer. Similarly, if products come into contact with the trailer walls, they may conduct heat from the outside.

Preventing Temperature Abuse by Tracking Reefer Airflow

At [Company Name], we recommend placing temperature monitors at eye level on the right side of the rear pallet (facing the door). This recommended placement covers areas prone to heat buildup, while also considering ease of placement and retrieval, providing a consistent standard operating procedure, and avoiding equipment damage.

So, why would the temperature recorded by the refrigeration unit differ from the reading on the temperature monitor? The temperature measurements recorded by the refrigeration unit are typically the supply air and return air temperatures.

For example, if pallets are stacked too high, air will circulate to the rear of the trailer.

Temperature monitoring devices installed at the rear of the trailer alert users to temperature issues caused by improper air delivery temperatures and insufficient airflow. With real-time temperature monitoring devices, organizations can identify shipments with poor airflow and intervene promptly to prevent quality degradation or spoilage.