, commonly referred to in the transportation industry as reefer trailers
, are semi trailers which feature an attached refrigeration unit used to refrigerate, or sometimes warm, the contents of the trailer. In general, these reefer trailers are used to ship goods and products which are temperature sensitive. A few examples are produce, meats, chemicals, medical supplies, and some computer components.
These reefer trailers provide a huge benefit to the transportation industry as they allow perishable goods
to be kept cold or frozen while being transported across great distances. Pacific coast seafood, farmed meat, and Alaskan salmon can be delivered to the east coast safely.
The refrigeration unit is powered by a small diesel engine. To begin the cooling process, a compressor inside the refrigeration unit, but outside of the trailer which is to be cooled, draws refrigerant in and compresses it. The pressure of this process liquefies the refrigerant gas and gives off heat. From there, the warm refrigerant is pumped into the condenser unit which acts as a heat exchanger allow its heat to be shed to the outside air. The now cooled, still pressurized liquid refrigerant is sent, at a controlled rate, into an evaporator unit located inside the refrigeration trailer. Inside the evaporator the refrigerant expands from a liquid state into a gas state. This process allows the refrigerant to absorb a great amount of heat from inside the trailer. The now warm refrigerant is then pumped outside the cooled area of the trailer, into the compressor, where the cycle begins again.