Refrigerator

A refrigerator is a cabinet- shaped device that is usually operated by electricity or LPG and keeps the temperature low own in its interior. By means of a commonly located at the rear and by thermostat -controlled refrigeration unit inside the refrigerator is cooled. Likewise, there are refrigerators on the basis of evaporative cooling or by cold outdoor temperatures are used.

Refrigerators are used for storage of food, medicines, chemicals etc. Due to the lower temperature undergo chemical reactions and biological processes that can, for example, food inedible and unusable drugs are slower.

The typical operating temperature in the interior of household refrigerators is between 2 ° C and 8 ° C. The housing of the cooling fan is thermally insulated to keep the energy required to maintain the difference to the ambient temperature low. Refrigerators are among the most popular and regularly used household appliances and thus have a significant share of household electricity consumption.

• 4.1 Temperature Zones
• 4.2 Ambient temperature
• 4.3 Energy Requirements
• 4.4 defrosting, maintenance
• 4.5 Star Rating for freezers

• 5.1 Freezer / Refrigerator Freezer
• 5.2 refrigerated

• 6.1 Environmental problems
• 6.2 Health Risks
• 6.3 repairs
• 6.4 switching
• 6.5 Transport and storage

History

Cooling has been achieved in ancient times, transported by ice from the mountains in places and in deep cellars (known as ice cellars ) for food storage began.

1748 William Cullen showed the first artificial cooling at the University of Glasgow. The modern refrigerator was marketed commercially in 1834, from Alexander twinning; its refrigerators cooled by air compression. An important development was the use of ammonia by Ferdinand Carré in 1859.

Until about 1950, wooden ice boxes, fed by ice from factory or pond were ( stored in the cellar under sawdust ) was used. They contain inside a vessel in brazed sheet zinc. Top ice ( crushed or whole, for example, icicles ) were charged, collected below the water dripping in the middle of a then surrounded by ice chamber is formed which receives the material to be cooled to ( marble ) subjects and is closed by a door. In Graz the addresses Eisteichgasse ( resettlement ) near the former brick clay pits and Am Rein and the place Rein remember this form of winter Eisgewinnung. In Vallorbe the ice from the Lac de Joux was loaded on the train for Paris, Zell am See afforded the ice for German breweries

For the development of the refrigerator was 1876, the German engineer and entrepreneur Carl von Linde in, the developer of fundamental of science and technology Linde process. His invention made ​​it possible to improve the reliability of the compressor and the entire chiller so that it was suitable for industrial use. Now you could make water ice all year industrially; it was no longer dependent on natural ice. His first development was still being operated with ammonia. This substance is corrosive and caused not only leaks but also a foul odor, so that refrigerators were suitable only in the 1920s for the development of replacement chemicals for domestic use. In the 1930s it became a standard in private households in the United States and Cuba; 1937 had every other American household refrigerator.

The first European refrigerator was founded in 1929 by the by Jørgen Rasmussen Skafte Zschopauer Motorenwerken JS Rasmussen developed. From the DKW brand - cooling was 1931, the German cooling and combustion engines GmbH forth in Scharfstein.

The first refrigerators operated with methylene chloride, ammonia or sulfur dioxide; this brought problems for the storage of the moving parts in the compressor and leaks the release of toxic gases or explosions with it. ( Was their ozone depleting and climate- changing effect was not yet known) With the discovery and use of chlorofluorocarbons substances these problems could be avoided.

The first CFC-free refrigerator in the world in recent times, was produced in 1992 by the Saxon company " dkk sharp stone " (later named " Foron "). It was suggested the development of Greenpeace and the Hygiene Institute Dortmund, headed by Harry Rosin. The first CFC-free refrigerator of this type has been converted by the Lare GmbH as a laboratory instrument for the Hygiene Institute Dortmund. The manufacturers of refrigerators at that time still had no interest in introducing this technology. Since 2000, household and commercial refrigeration equipment with flammable refrigerants are becoming more and more present on the market. The system cools the so-called " Dortmunder mixture ", a mixture of propane and butane, which neither increase the ozone hole still contribute to the greenhouse effect, but it is flammable.

With the spread of electric current and the refrigerator lost its precursor, the electroless freezer, attractive. The word ice box ( ice chest in Austria ) is colloquially used to in our time for the refrigerator in use today.

Operation

For all types of refrigerators is extracted by means of heat exchangers to the interior of the refrigerator and heat emitted to the environment (see chiller and heat pump). After the manner in which this is achieved, one distinguishes three types: Compressor refrigerators Absorption refrigerators and refrigerators with Peltier element.

Compressor refrigerator

On this principle that the cooling systems are commonly used in household and industry: With the compressor fridge, a gaseous refrigerant is compressed by a compressor adiabatic ( without heat exchange with the environment ), thereby heating the refrigerant. In the condenser, consisting of black and cooling coils mounted on the back of the device, the heat is released to the environment, whereby the medium condenses. Then it passes to the pressure drop through a reactor - for example an expansion valve or a capillary tube - and then to the evaporator inside the refrigerator. This removes the evaporated refrigerant from the refrigeration compartments the necessary heat of evaporation ( evaporative cooling ) and flows as gas continues to outboard compressor. A refrigerator compressor is functionally equivalent to almost a heat pump, it differs only in the use of the heat exchanger. The temperature is controlled with a thermostat, the compressor depending on the desired temperature on or off.

Absorption refrigerator

The absorption refrigerator uses a water - ammonia mixture. In the boiler (eg gas flame, electric heating, solar heat ) are separated ammonia and water by heating. Thereafter, the liquid water and the gaseous ammonia is passed through various pipe systems. The ammonia is condensed in the condenser; Here are the refrigerator heat to the environment. An evaporator in the interior makes it again gaseous - at this point cools the refrigerator. Subsequently, the ammonia is merged in the absorber with the water. For a detailed functional description can be found in the article of the diffusion absorption refrigerator. Absorption refrigerators are used for example in motor vehicles or camping supplies. You have, at least in electric mode, less efficient than compressor refrigerators. If they are powered directly by gas or engine heat, they are about as effective as compressor units through the direct use of primary energy. Except the working fluid, since they have no moving parts, they are virtually inaudible; this feature gives them a wide range of applications, for example as mini bar in hotel rooms. For use in particularly remote areas, there are also absorption refrigerators with petroleum operation.

For small absorption refrigerators for campers, caravans and for hotel rooms Electrolux is practically the sole European leader (2008) (product name Electrolux RM nnn ). The brand is sold the same design under the name " Dometic ".

Advantages of absorption refrigerators

• Noiseless and vibration free
• Operation with gas

Disadvantages of the absorber cooling system

• Poor efficiency, higher energy consumption
• Power drop from 35 ° C outside temperature possible
• Movement and skew- sensitive
• Defined construction of the absorber cooling system
• Due to the low production numbers more expensive than comparable compression refrigerators

Thermoelectric Refrigerator

View Mobile Application (Peltier effect) for years spread coolers on the thermoelectric principle offered. You work directly with 12 V DC and are therefore ideal for use in the car. They also work in principle completely silent, but are usually supported by fans that produce a certain noise level. The benefits are achieved at the expense of an extremely poor efficiency: While a compressor refrigerator for transmitting 1 Watt " cooling power " about 0.5 watts consumed, requires a Peltier element for the same energy transport over 2 watts. The use of these devices in the household is therefore energy technology does not make sense.

Construction

A typical table refrigerator ( floor model ) has about 150 liters and weighs about 40 kg. A cooling -freezer has 250 liters and weighs about 65 kg.

There are various floor plans for refrigerators. The best known and most commonly used is the variant with a large outer door and an inner door to the freezer compartment at the top. The freezer compartment usually has a maximum capacity of 20 liters, the refrigerator compartment can sizes up to 250 liters assume (possibly larger).

Other variants have separate doors for refrigerator and freezer. They are referred to as refrigerator-freezer combination. The compartments may lie one above the other or side by side; latter version is very popular especially in the U.S. and usually has a built in ice maker and optionally an additional drinks flap in the great door of the cooling segment. Such " side-by- side" refrigerator - also known as American fridge - can accommodate more than 500 liters ( about 350 liters refrigerator, freezer about 150 liters).

Larger versions have, for example, via a double door to the overhead cooling area and down over a very wide drawer for the freezer segment. These variants are called French fridge.

Operation

Temperature zones

In a modern household refrigerator prevail different temperature zones:

• Above it is the warmest, there can cooked foods and jams are stored well.
• In the central region, among other dairy products ( yogurt, cheese) are in good hands.
• The coldest is about 2 ° C below the compartment above the vegetable bins. Here are perishable things such as meat and sausage.
• The drawers at the bottom are from about 8 ° C low in fruit and vegetables. Under temperature and humidity of the cover are adapted to receive vitamins and appearance of the product.
• In the door pockets, it is relatively warm, but cool enough for butter and eggs.
• Newer, high-priced refrigerators have also partly a 0 - ° C- cooling zone, the food will keep fresh very long.
• Another new feature is the decoration of a extra compartment for fruit and vegetables with LEDs that light up when the door is closed on. These are for example two flashing LEDs that simulate the blue and green portion of sunlight. In this way, the natural protection mechanisms of fruit and vegetables to be activated in order to counteract the vitamin degradation, which occurs during storage in the dark.

Ambient temperature

In refrigerators with freezer compartment, particularly with freezer compartments, is the manufacturer's specified ambient temperature of the installation location, given as climate class, consider:

While a low ambient temperature of the site helps initially, to save energy, leads - paradoxically - that is below the minimum temperature to a thawing in Eis-/Tiefkühlfach. This is due to the fact that the fridge and freezer compartments usually have a common compressor that is controlled by a thermostat in the refrigerator. At a low temperature, eg, 8 ° C, the compressor has to run only rarely, for example, to ensure a temperature of 6 ° C in the refrigerator. This activity of the compressor is not enough to work against the much larger difference ( heat flow ) between the outside temperature and the temperature in the freezer compartment, such as -18 ° C, . Other than that can be too thick below the minimum operating temperature lubricant in the compressor.

Refrigerators to climate class SN often therefore have a heating near the thermostat in the refrigerator of about 8 watts. Sometimes simple is the bulb (usually 15 watts). Turned not to extend the operating temperature of the climate class N to SN [ evidence ?]

Who wants to save energy and install a refrigerator in an unheated room, which also sustained temperatures are expected below 10 ° C, chooses better against a fridge freezer and a separate refrigerator and freezer or even better for a freezer. Lately, set in private households more and more small refrigerator and freezer cells by. For commercial users, there are still some other cooling devices, such as Wall Display ( for presenting mainly packaged foods ), free cooling counter, Beer cooler, etc.

Some grocery stores offer drinks - in boxes - cool temperature in normal shelves by placing a small region of lower ceiling height is designed as a cooling chamber which is to enter only by an approximately 1 m wide pretty airflow dense, transparent film strip curtain.

Energy demand

The energy requirement is defined in Central Europe for ambient temperatures between 16 ° C to 32 ° C and classified as N climate class. The Energy Labelling ( colloquially Energy label ) from 1998 is used to support the purchase decision. The range extends from G to A and reflects the state of the art at the time resist. For more energy-saving refrigerators and freezers 2003 extensions A and A are introduced, each better than the energy efficiency class A and are available for a very low energy consumption.

The European Parliament adopted the Directive 2010/30/EC in May 2010, in force from 2011 revision of the energy efficiency classes for household appliances. In addition to classes A and A is also introduced the Class A and displayed on the energy label. The new A 5% may consume more energy than the old A class and the new A may need 10 % more.

Old Directive for household appliances: refrigerators for 92/75/EEC: Directive 94/2/EC amending Directive 2003/66/EC

New Policy for household appliances: refrigerators for 2010/30/EU: Commission Regulation ( EU) No 1060/2010

In the new policy is set, that since July 2011, may be placed on the market no longer poorer household appliances with compressors as class A ( eg absorber devices may still be significantly worse ).

1983 built the Rocky Mountain Institute ( RMI), a Sun Frost refrigerator with only 0.19 kWh / l per year, the heat exchanger was installed outside the building and half of the required cooling energy was generated passively. RMI holds a development of devices with even lower fuel consumption, for example by vacuum insulating layers, is possible. The most economical Fridge-Freezers achieve fuel consumption of 0.48 kWh / l per year ( at 25 ° C ambient temperature) as the Blomberg CT 1300A ( no longer commercially available ) or 0.34 kWh / l per year (at 21 ° C) Sun Frost RF16 the. A similar device, the energy efficiency class A requires 1.26 kWh / l per year ( as of 2006). Much more economical are pure refrigerators without freezer. These are then recommended if in any case a separate freezer is available.

Defrosting, maintenance

The maintenance by the defrosting of refrigerators is to prevent, measure around the waste of energy. When you open the refrigerator door lets warm air enter the refrigerator interior. If the door is closed, the refrigerator, the internal temperature is lowered again. However, since colder air has less capacity to absorb moisture, so it is saturated faster, condenses the excess water and deposited in the form of droplets on the surfaces and from freezing. Icy Condensate cooling surfaces lose their power output because the ice acts as an insulator. This means that the refrigerator for the same power, more energy has to spend ( current).

Modern refrigerators and freezers typically have a self-defrosting in conjunction with the No- Frost technology. While the no- frost technology has a preventive effect by lowering the moisture, thereby reducing the formation of ice, the defrosting is curative in already formed ice used. For models from the middle price range, the automatic defrost for the refrigerator part is since about the 1980s standard, while it is common in the freezer only models in catering quality. Refrigerators earlier model years must be defrosted manually, by going off a few hours and the ice sheet, which has formed on the inner back wall of frozen condensation can drain through liquefaction in an extra container or removed manually. A technique to avoid this problem is to provide a circulation system inside the refrigerator that the air an evaporator - outside of the actual cooling space - is supplied to the then ice forms. This evaporator again defrosted regularly off independently, and the resulting liquid is collected outside of the device into a drip tray and can support there evaporate through the compressor waste heat. Thus, the air in the refrigerator is dry, and it is hard to form ice.

Another technique that has been used, for example in the refrigerator compartment of the refrigerator-freezer BBC Duplo from the 1970s, is that at the back of the upper rear region of the refrigerator compartment mounted vertically plate-shaped evaporator, a heating plate is attached (in the said device 20 watts ), which is in each case automatically switched on when the compressor is stopped by the thermostat and the restart at the same time shuts off. The defrost water is possibly present among collected in a flat, built in the inner back wall funnel which has the connector on the back of the refrigerator. There the water is directed through a tube down to the open container. This is the coolant line directly at the outlet of the compressor - where these relatively high temperatures reached - heated, so the condensate can easily evaporate into the environment; characterized it also contributes to the energy in cooling the compressed cooling medium in the condenser, a part of the energy consumed in the defrost heater plate energy is recovered here.

Since about 1995, the cooling surface of the refrigerator compartment in the inside back wall is often integrated as the evaporator must be better protected for safety reasons due to the introduction of the flammable refrigerant R600a. After the cooling phase is waits until the surface has 5 ° C to allow the frost thaws deposit formed there. The water runs down to a funnel-shaped channel and through a 10 mm hole and the outside in a cup on the compressor, the heat evaporates the condensed water. In operation, it should be noted that there is nothing from the refrigerated items on the back wall, since the condensation else runs into the refrigerator. The drain hole must be kept free of obstruction. Some are covered with dust caps, which are plugged with a resilient extension into the drain opening. For once recommended annually undercutting of runoff, for example, is a straw. In these types of devices only any existing freezer must be defrosted specially.

Star Rating for freezers

Related Refrigerators

Freezer / Refrigerator Freezer

Freezers and freezers operate on the same principle as a refrigerator, but cool with an internal temperature of -18 ° C and colder, making the long-term storage of frozen food is possible. With 4- star freezer foods can also be frozen. They are usually equipped with a separate Quick freezer ( it is usually located above and is equipped with a separate flap, while the other like a drawer freezers work).

A freezer needs a lot more power than a same -sized refrigerator.

Refrigerated

In supermarkets special open cooling devices are used to store foods that require a permanent cooling, easily accessible to customers. Since in this case, takes place unlike closed cooling devices, a constant exchange with the warmer ambient air, the energy consumption is significantly higher.

Freezers with access from above have in the past covered overnight with simple plastic covers, since about 2005 are sliding lid made ​​of insulating glass (two panes, metallised ) usual.

Freezing cabinets with access from the front ( increase the trade turnover per area ) have self-closing doors with hold-open device and insulating glass heater to prevent condensation. Signs such as " select - only then open " to limit warming.

At the front of chiller cabinets without doors there is a constant stream of cold air down, the collected there, cooled and blown creeping up again. At night they are sealed with aluminized curtains of plastic foam.

While previously the dissipated heat chillers was delivered to each cooling unit in the business area, the waste heat is conducted into newer business premises by insulated refrigerant piping circuit in an energy center that serves the air-conditioning (heating, cooling, ventilation ) of the rooms and the hot water.

Problems

Environmental problems

Refrigerators in the household employed work on the compressor principle. The CFC-containing refrigerants used there as a refrigerant for a long time are ecologically very worrisome, because they have a strong ozone depleting. In addition, the foam materials used in the insulation were also inflated with CFCs. However, because CFCs are released only when scrapping of the refrigerator, the refrigerator in question should not be replaced prematurely because of this. When one is foaming in the 1990s, for example, switched to n -pentane. In newer refrigerators mainly other refrigerants such as isobutane or R134a can be used since the mid- 1990s. The refilling of refrigerators or air conditioners with original CFC-containing refrigerants is banned, or only with appropriate non-CFC replacement refrigerants allowed. Older, already installed industrial cooling equipment are excluded from this regulation.

In winter, the operation of refrigerators is particularly inefficient because the device often in heated rooms ( eg kitchen ) is available and has to cool down it from the elevated ambient temperature. This was previously avoided by the refrigerated one housed in the cold season in a closet with connection to the outside world.

Health risks

According to a study by Jean -Pierre Hugot Hôpital Robert Debré from Paris it could be that the climatic conditions within a refrigerator favor the spread of certain cold-loving microbes such as Yersinia and Listeria. These microorganisms may be cause of Crohn's disease ( disease of the digestive system ). The consumption of spoiled food due to waiver of the cooling should, however, be subject to greater risk of disease.

The Federal Institute for Risk Assessment According to the anti-bacterial silver coatings used by many manufacturers superfluous in refrigerators. A possible consequence of the use of antibacterial silver coatings is the transfer of silver in foods. Silver inhibits the growth of bacteria, but is essentially harmless to the human organism, therefore permitted ( in addition to gold and aluminum) as a food color.

Repairs

Components such as the compressor, the starting device of the compressor, and the thermostat is subjected to higher stresses. While the replacement of a thermostat can be done by almost every electrical operation, you have to contact the repair service of the equipment manufacturer or a specialized company for refrigeration at a damaged compressor normally. The replacement of a compressor can be so expensive that a change of the entire cooling unit is likely to be more economical, since not only the compressor, but also the entire refrigerant charge must be replaced. The starting device is subjected to high currents and high temperature differences. For custom - designed and environmentally friendly cooling appliances it can be replaced separately from the compressor.

If a cooling surface of aluminum, usually produced by roll -bonding and inflation - for example through improper help out during defrosting by scratching or bumping - perforated, a repair is hardly worthwhile. While there is a bonding process, but it is expensive, and the refrigerant circuit must also be checked and refilled in a specialist workshop for leaks. The place to be bonded is only accessible from the outside while the inside pressure acts. A bond is stressed by high humidity and frequent strong temperature changes. Easy to repair the rupture of a pipe to the evaporator appears rear. Copper tube can be soldered well.

Turn on

If a compressor fridge off, the compressor can run did not immediately return to the still existing in the condenser pressure. After some time (one to two minutes) equalizes the pressure of the reactor and the capacitor, and the starting is possible again. The built- in fridge rules comply with this waiting time automatically. However, if removed during operation of the plug, it should be plugged in again after a few minutes, so as not to unnecessarily overload the compressor drive. If the plug is still plugged in again immediately, after unsuccessful attempts to start caused by a ( self-resetting ) Motor protection switch a wait.

Transport and storage

If a is laid out for standing operating compressor refrigerator transported long periods of time lying, then lubricant may have shifted from the compressor into the cooling circuit. In this case, the refrigerator should only about twelve hours standing in its normal position before it is put back into operation. Wherein the lubricant is given enough time to flow back into the compressor.

If a used refrigerator temporarily put out of service, should remain the refrigerator door open to prevent the formation of mold.

Through contained refrigerant cooling machines fall (incl. Kühlagregat ) under the UN number 3358th However, the special provision 291 exempted from ADR, as long as less than 12 kg of gas is included. If a non-flammable gas is contained, UN number shall 2857th Again, there is a special provision 119 which does not make up to 12 l or kg gas content in these chillers use of ADR is required.