The purpose of refrigerated systems for cold storage is to maintain or extend product life. Refrigeration systems for cold storage are applied to processing, manufacturing, and warehousing food, biomedical materials, ice manufacture, and other uses; but the largest application is for the refrigeration and freezing of foods.

Refrigerated systems provide much lower temperatures than comfort air conditioning systems. The design, selection, and construction of refrigeration system is different and can be more intensive than that for a comfort air conditioning system. For this reason, the refrigeration industry has evolved into a separate and distinct industry.

There are two process-freezing techniques - contact freezing and air blast freezing.

These type freezers have lower operating costs, particularly from the standpoint of the amount of refrigeration required to accomplish the freezing and the cost of the associated energy required to do the freezing.

Contact freezers are most commonly referred to as plate freezers, as the freezing media are flat plates to which the food products are brought into direct contact. The plates are hollow between the two flat surfaces which the product contacts. Cold refrigerant flows through the hollows, chilling the plate surfaces and thus freezing the product.

Horizontal plate freezers are most commonly used for packaged product. It is important to note there are limitations on the kind of packaging that either vertical or horizontal plate freezers can handle, relative to the shape of the package. Moreover, the plate spacing must be mechanically set for a given size package so that only one package size can be accommodated at a time. If it is desired to process a different size package, the plate spacing must be reset. This is an obvious limitation to the versatility of the plate freezer.

Air blast freezers are also produced in two varieties: batch and continuous. Batch-type air blast freezers are of quite simple construction and are thus much lower cost than continuous freezers. Typically they are used for packaged and palletized product, although they are also used for loose product in totes, barrels and bins. A blast freezer of this type is often comprised of a small room that can be closed off from the rest of the facility, but with a large door for ease of access with fork trucks, a rack system for holding the product in a preset geometric array during freezing and a powerful air-cooling unit.

Unpackaged product is frozen in this kind of freezer. It too comprises a room that is closed off from the rest of the facility, the only openings in which are the conveyor openings for the inflow and outflow of the product, and access doors for personnel. The cooling coils are typically very large and the fans are mounted remotely from the cooling coils so they can be located strategically to optimize airflow for the most efficient cooling.