Refrigerator
A
refrigerator (colloquially fridge) is a common household appliance that
consists of a thermally insulated compartment and a heat pump (mechanical,
electronic, or chemical) that transfers heat from the inside of the fridge to
its external environment so that the inside of the fridge is cooled to a
temperature below the ambient temperature of the room. Cooling is a popular
food storage technique in developed countries and works by decreasing or even
arresting the reproduction rate of bacteria. The device is thus used to reduce
the rate of spoilage of foodstuffs.
A
refrigerator maintains a temperature a few degrees above the freezing point of
water. Optimum temperature range for perishable food storage is 3 to 5 °C (37
to 41 °F).[1] A similar device which maintains a temperature below the freezing
point of water is called a freezer. The refrigerator is a relatively modern
invention among kitchen appliances. It replaced the icebox, which had been a
common household appliance for almost a century and a half prior. For this
reason, a refrigerator is sometimes referred to as an icebox.
Freezer
units are used in households and in industry and commerce. Most household
freezers maintain temperatures from -10 to 0 °F (-23 to -18 °C), although some
freezer-only units can achieve −30 °F (−34 °C), and lower. Refrigerators
generally do not achieve lower than -10 °F (-23 °C), since the same coolant
loop serves both compartments: Lowering the freezer compartment temperature
excessively causes difficulties in maintaining above-freezing temperature in
the refrigerator compartment. Domestic freezers can be included as a separate
compartment in a refrigerator, or can be a separate appliance. Domestic
freezers are generally upright units resembling refrigerators, or chests
(resembling upright units laid on their backs). Many upright modern freezers
come with an ice dispenser built into their door
Some
refrigerators are now divided into four zones to store different types of food:
−18 °C (−0 °F)
|
Freezer
|
0 °C (32 °F)
|
Meats
|
5 °C (41 °F)
|
Refrigerator
|
10 °C (50 °F)
|
Vegetables
|
Table
1: Temperature
The capacity of a
refrigerator is measured in either litres or cubic feet. Typically the volume
of a combined refrigerator-freezer is split to 100 litres (3.53 cubic feet) for
the freezer and 140 liters (4.94 cubic feet) for the refrigerator, although
these values are highly variable.
Temperature
settings for refrigerator and freezer compartments are often given arbitrary
numbers by manufacturers (for example, 1 through 9, warmest to coldest), but
generally 3 to 5 °C (37 to 41 °F)[1] is ideal for the refrigerator compartment
and −18 °C (−0 °F) for the freezer. Some refrigerators are required to be
within certain external temperature parameters to run properly. This can be an
issue when placing units in an unfinished area such as a garage.
European freezers, and
refrigerators with a freezer compartment, have a four star rating system to
grade freezers.
Temperature
|
Time Storage
|
min temperature = −6 °C (21 °F).
|
Maximum storage time for (pre frozen) food is 1
week
|
min temperature = −12 °C (10 °F).
|
Maximum storage time for (pre frozen) food is 1 month
|
min temperature = −18 °C (−0 °F).
|
Maximum storage time for (pre frozen) food is
between 3 and 12 months depending on type (meat, vegetables, fish, etc
|
Table
2: Temperature And Time
