Insulated Bulkhead Thickness, and Reefer Configuration

Without it, refrigerated units would cry foul and achieve little. The magic is called Insulated Bulkhead. The insulation retains cooled air inside, keeping perishable cargo at the proper temperature and extending the life of the cargo.

Food service trailers are typically more rugged than long-haul refrigerated trucks. This is because customers want strength and durability in every component so they can operate for 10 to 20 years. Long-haul haulers want lighter weight to carry higher payloads, so they specify items such as aluminum structural members and thinner walls. Such trailers wear out more quickly, but the life cycle of the program is correspondingly shorter.

Insulation thickness

Insulation of walls, tops, floors and doors must be adequate. The "Ua" value is a measure of the trailer's thermal efficiency; the higher the Ua value, the more cooling is required. Over time, the insulation will degrade - crumbling, absorbing moisture, etc. - and heat and cold will move more easily from the outside and inside of the trailer.

The type of Insulated Bulkhead varies by trailer and body manufacturer, with some claiming superiority over others. In general, more means greater capacity and is more related to wall thickness. Walls can be as low as 1.5 inches thick for produce trucks that also haul dry goods, while Insulated Bulkheads can be up to 6 inches thick for trucks that haul ice cream. Obviously, the desired commodity temperature determines how much insulation is needed.

Trailer Configuration

Size is always important, but it's not the only thing that matters. The amount of insulation determines the amount of cooling required, and airflow is more affected by the length of the trailer. Airflow around the product is important and air chutes are usually recommended, especially in longer trailers and where constant temperatures are required throughout the loading process.

Trailer Body Color

This affects the "solar gain" - the darker the truck body, the more solar heat it will absorb and the more cooling capacity the TRU will need.

Number of doors

Swing doors are usually more completely sealed than roll-up doors. Side doors add ease of delivery, but introduce more openings through which cold air will be lost.

Type of flooring

It is best to have a floor with channels that promote airflow under the load, rather than a flat or "diamond plate" type floor. Pallets are a necessity on flat floors to ensure proper air flow and temperature control.

Operational Issues

Contents and temperature

What kind of product will be carried and how large is the load? What temperature set point is required and is the product loaded at the correct temperature or must it be "pulled down"?

Ventilation

Cargo such as fresh produce "breathes" and generates heat and moisture, which sometimes must be removed from the trailer. This is why small ventilation doors are installed in the nose and one of the rear doors.

Delivery

How many of these doors will be opened for delivery and for how long? What is the average time interval between delivery stops? There are few door openings for long trips, but there are many local delivery trailers that require reefers that can recover quickly from intermittent heat increases.