Both industrial refrigeration and air-conditioning are based on the same mechanism: a fluid, generally water or air, is cooled by evaporation of another fluid, called the refrigerant. The refrigerant circuit, comprising the compressor, evaporator, condenser and expansion device, is an integral part of both systems. Nonetheless, there are substantial differences between refrigeration and air-conditioning systems, for example as regards the components, the design methods, the commercial or industrial structures where they're installed and their operation, such as to justify the existence of two distinct market sectors.
Refrigeration is the process involving a reduction in the temperature of fluids or bodies in general. Specifically it's used for temporary storage of perishable goods, at temperatures down to -60 °C.
Refrigeration is one of the most important applications in the food industry, as it slows down the growth of bacteria in food, preserves organoleptic properties and extends shelf life.
The main appliances used in commercial and industrial refrigeration for food preservation are:
- Cold rooms;
- Supermarket showcases;
- Showcases in patisseries, bar, ice cream parlours, etc.;
- Refrigerators used in industrial kitchens, including maturation rooms and retarders;
- Refrigerators for pharmaceutical products;
- Blast chillers.
These differ mainly as regards their appearance, depending on whether the product needs to be visible to customers, as well as in terms of several fundamental aspects such as standards compliance and the cooling performance required; the latter may, for example in blast chillers, involve high cooling capacities over very limited periods of time.
The major foodstuffs that require preservation at temperatures just above 0°C are matured cheeses, drinks (beer, wine, fruit juice, soft drinks), cold meats and delicatessen products in general.
Meat, fish, fruit, vegetables and fresh dairy products are stored at around 0°C.
Negative temperatures down to -25°C are used to preserve ice cream and other frozen or quick-frozen foods in general, for example fish or vegetables, produced using processes that extend shelf life.
For the operating principles of refrigeration systems and refrigerant circuits, see "MAKING IT COLD".