An important thing to consider when loading your refrigerated vehicle is to allow airflow around your product,this will keep all areas of your product cool and balance the air temperature in the load space.
Refrigeration works by drawing up warmer air that passes around your product up into the lower side of the evaporator ,this work is carried out the by evaporator fans.This warmer air is pushed passed the evaporator core and out over your product at a slightly lower temperature,this cycle continues slowly lowering the temperature until it reaches the set temperature.
Loading therefore is vital to the operation of your refrigeration unit allowing correct flow of air around your product.The alternative is that you block this airflow keeping cooler air from the evaporator at the evaporator end of the compartment.
So keep space above,to the sides and to the bottom of your product by use of pallets or other means.Many larger trucks have airflow floors allowing air to pass under the product.The down side to incorrect loading is that when you open the back door to load or unload warmer air enters and is then trapped in the rear ,warming up the product to the rear,again not allowing airflow to the front where it needs to flow through the evaporator.
When unloading try to use the side doors as the rear doors are usually larger allowing more warmer air to enter.Turn off the refrigeration unit when opening doors as the fans will blow the cold air out or use door curtains.
Internal walls with fan kits allow temperature variations,freezer in the front and chiller in the back.