You could be forgiven for thinking the mechanism of a freezer van is incredibly complex. After all, it does perform a reasonably impressive task, and often people assume the inner workings of machines, even incredibly widely used machines like freezer vans, are incredibly complex. The truth is that the mechanism of a freezer van is simple enough that anyone can understand it.
At the top of a freezer van you’ll see an extra piece of equipment that wouldn’t be present on a non-refrigerating version of the same type of van. This is known as the evaporator, and it’s an essential piece of equipment for keeping the temperature in the van low. However it’s just one element of the system. The rest of the machinery you’ll find on the inside roof of the freezer van compartment.
The other elements are known as the condenser, and the compressor. The condenser is a thin length of metal piping, twisted into a shape similar to a radiator to provide maximum surface area in a small space. The piping is filled with a specially developed coolant fluid. This fluid has been developed in high tech laboratories to have a chemical make up that makes it particularly good at absorbing heat. As the coolant fluid circulates through the condenser, it will gradually absorb the heat inside the freezer van compartment (click here for more on our freezer vans). This makes it heat up, and because it has an incredibly low boiling point it will quickly change into a gas.
At this point, the compressor will take the gas and compress it down so it reaches an extremely high pressure. Once the gas has been sufficiently pressurised, it is introduced into the evaporator, the aforementioned piece of machinery that you see on the top of the freezer van. The evaporator works by pushing air from the outside through the high-pressure coolant gas. The gas then cools down, becomes a liquid again, and is re-circulated through the system. Meanwhile the heat that was stored in the high-pressure coolant gas is released into the atmosphere.
There are other elements of the system, such as machinery to regulate the pace at which this system operates, but this is basically how it all works.
The other element of the freezer van is much less technical, but no less vital to maintaining a low temperature. It’s the thick layer of insulation that surround the freezer van’s cool compartment, keeping heat from getting into the compartment from outside. The insulation is absolutely vital, because without it the coolant system previously described would become overworked to the point of redundancy, not just because of the heat that is coming in from the outside of the vehicle but also the heat from the running of the engine.
The insulation is almost always comprised of an extremely thick layer of foam. The foam is made from a polymer, and it usually t quite similar to polystyrene, although it will have much more density and durability than the type of polystyrene you’d find in packing materials or a cheap picnic cooler. The thickness of the foam used is the main difference between a freezer van and a standard refrigerated van. If the van is intended to be operated at extremely low temperatures then the foam will need to be very thick indeed.