Refrigerator
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A refrigerator is an appliance used to keep objects cool by the use of a heat pump. The vapour compression is a method that is used most commonly in household refrigerators. This method can be compared to that of the body using sweat to lower its temperature. In the kitchen, refrigerators (or fridges) are used for the conservation of food by slowing down the degradation of food and by limiting the development of micro-organisms. According to Michel Jurdant[1], in the mountains of Pindos, central Greece, the villagers claim they don't need fridges because when they kill a goat or a sheep, they share it with their neighbours ; they will later return the service. This shows that technological progress does not necessarily mean social or cultural benefit.
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[edit] The history of refrigeration
Formerly, people used to cool food with ice ; iceboxes can be said to be the ancestor of fridges, fresh ice was regularly added. Cellars were also a common means of conserving food. The physical principle of refrigerators was first invented in 1876 by Carl von Linde. Other inventors had worked on this and it took time to develop the technology till the Swedish inventor Baltzar von Platen had the idea of using the absorption of gas in 1922.
[edit] Principle of operation
A refrigerator contains a volatile refrigerant which circulates in a closed loop. When this fluid is compressed in a specific compressor at a high temperature, then it is a gas that gradually liquefies as it flows along the condenser. The fluid will then become vapour again travelling through the coils of the evaporator. This causes the absorption of the calories (heat) which is inside the refrigerator. The cycle keeps repeating itself. The heat that is absorbed within is let out. Fridges need Energy to make the pump of the compressor work.
[edit] The characteristics of refrigerators
[edit] Household refigerators
Household refrigerators have a main compartment at a temperature of 39 to 80°F. One finds more and more refrigerators which also act as freezers. Apart from external dimensions (in.), one measures the capacity of a refrigerator in cubic feet. Older refrigerators used R12, more commonly called it freon as a cooling agent. Freon, or R 12 belongs to the family of CFC responsible for the depletion of the ozone layer. Today, they're forbidden.
[edit] Important warning
- a refrigerator using a compressor should not be turned over or bent down so as not to diffuse the oil of the compressor all along the circuit. As oil is not easily compressible, the compressor utterly destroyed. * Never de-ice the evaporator of a refrigerator with a knife, which would provoke refrigerant leaks. * CAUTION!! More and more refrigerators use a fluid containing BUTANE, ISOBUTANE R600A, never try to mend it yourself, never bring a flame near it, in case there is a leak, make sure you aerate the room.
[edit] Energy savings
A refrigerator is supposed to last for about 15 years. Over this period, its electric consumption can prove more expensive than its purchase price.
[edit] Choosing the right model
Compare the various models, mind their respective energy consumption (mentioned in kWh (kilowatt-hour). In France, refrigerators are ranked according to their consumption using letters ranging from A++ to G. The most cost-effective and energy efficient ones are labelled as A+ or A++. Side-by-side refrigerators consume much more electricity. The size of the refrigerator should be in keeping with the way you use it.
[edit] Use
The energy consumption of a refrigerator depends directly on the ambient temperature. If the temperature is 73°F instead of 64°F in the kitchen, the consumption of the refrigerator will increase by 38%. Don't put the appliance in a cold place in Winter or in a hot one in Summer, (balcony ) as the compressor would need more electricity. Do not leave the door of the refrigerator for too long or don't open it too often. A refrigerator must be de-iced regularly. One inch of frost means 30% of extra consumption. Never place hot food in your refrigerator. Let cool down at ambient temperature before. Conversely, frozen food can be put to defrost in the refrigerator for a few hours. Make sure the seals are tight. To test their effectiveness, simply insert a paper sheet and shut the door : you shouldn't be able to take the sheet out, if you can, change the seal. Mind there's no heating appliance near the fridge. Let space between the wall and the fridge (about 2in) so you can clean the dust behind (it soon makes an insulating layer!).
[edit] Hygienics
Food contains bacteria. Their development is not prevented by the cold, it is simply slowed down. Several measurements make it possible to avoid the contaminations of a piece of food to another one :
- Place the food according to the zones of temperature (see the instructions or check with a thermometer):
- In the coldest zone : fish, meat, cooked dishes
- In the intermediate zone: dairy products
- In the least cold zone (in general, they are the vegetable compartments and the door): fruit and vegetables, eggs, industrial sauces
- Regularly control the temperature which must remain stable between 37 and41°F.
- Remove useless wrappings such as cardboard around yoghurts.
- Cover the food with a lid or cellophane.
- Mind the best before indications.
- Don't leave rotten fruits or vegetables or products that are past their use-by date.
- Clean the refrigerator regularly : you can use natural soap, lemon, vinegar
[edit] See also
[edit] Internal links
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[edit] References
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