Already in the 12^th century the Chinese people knew how to cool down water with the help of some chemical reactions. In Europe the first man who tested the methods of cooling down drinks was the physician Blasius Villafranca. He also described it in his document Methodus refrigerandi (methods of cooling down), we have already mentioned it while talking about the icecream´s finding. In 1607 L. Tancredus made the first synthetic ice in Europe. In 1676 a corporation of the fruit and flowers refrigerate masters was established in France and it had more than 250 members.

The direct predecessors of the nowadays fridges were those, which used the cooling abilities of the natural ice. Whey appeared in England around the year1790 and had a metal facing of the diaphragms into which the cubes of ice were inserted. Their deviser was most probably Scottish physician W. Cullen. Focard- Chateau had patented a similar fridge in France in 1801.

Cooling with the natural ice survived a long time. Still in the 50s it was possible to see the ice blocks to be cut on the frozen rivers and lakes. The blocks were than stored in the ice-houses, where they sustained until the next winter.

But to bank on the natural ice was a bit unsure and so the devisers tried to construct a machine, which would produce synthetic ice. The first success was achieved by an American deviser Jakob Perkins who got a patent for a cooling machine with ether fumes, cooling snake and an evaporator. This happened in 1834.

The real ”father” of artificial cooling was the French Ch. Tellier. First (in 1869) he arranged cooling of meat in an ammoniac machine on the steam-boat City of Janeiro and later he built large cold stores not far from Paris.

But this appliance was not suitable for households. Only its dimensions were too big, it would occupy the whole kitchen. An upturn was caused by a German physician Karl Paul Gottfried von Linde in 1875, he devised an ammoniacal cooling machine with a compressor. A non-compressor absorbent fridge was produced in 1923 in Sweden.

The first vegetables, fish and meat chilled in packets were sold in 1930. The first food-stuff, which was pre-cooked, so that it was only necessary to warm it up, was first sold in 1939.

History and the present

And what principle do the refrigerators work on? The whole activity of the cooling mechanism is based on an exceptional attribute of the refrigerant: first it has to evaporate at the low pressure and temperature and so take away the warmth to its surrounding and second it has to condense at the higher pressure and temperature and so deliver the warmth to its surrounding. The evaporation at the low temperature is the essence of the cooling mechanisms, on the other hand the condensation at the higher temperature is the essence of the thermal pumps which are used for heating.

In the fridges with compressors the refrigerant circles in such way, that the compressor (the black snarling thing behind) takes up the refrigerant fumes from the evaporator (the box inside above, where the food-stuff get chilled), presses them and force them into the condensator (the black grate behind), where they condense. Than the refrigerant comes back into the evaporator. There the refrigerant evaporates because it takes away the warmth from the food-stuff. The food-stuff is cooled down. The fumes are taken up with the compressor again and the whole cycle is repeated until the inside of the fridge doesn’t have the temperature set with the thermostat (the gadget with numbers inside the fridge).

The fridge with compressor

In the absorbent fridges the cooling is based on the principle of absorption – one substance absorbs another one, which is accompanied with thermal changes. The main part of the absorbent cooling mechanism is the evaporator, absorber, expeller and a condensator. By warming up the refrigerant with water in the expeller (this can be done either with an electric heater – electric absorbent fridges, or with a gas burner – gaseous absorbent fridges) the fumes of refrigerant are expelled from water, these fumes course to condenser and here they condense. From here the condensed refrigerant gets into the evaporator. Thus the cycle is the same as at the compressor fridge (the compressor is replaced with an evaporator and an absorber). The advantage of the absorbent fridges is their noiseless working. But they cannot cool the inner space to such low temperature as the compressor fridges, because they have lower efficiency (and the running is also more expensive).

Lately the separate freezers are more and more popular. Thanks to the fact, that the temperature is the same in the whole space, it is possible to reach even very low temperatures (up to -30°C). Under such conditions the food-stuff can be stored very long.

When buying a fridge or a freezer we should prefer products, which use isobutan (R600a) as the cooling medium. This does not damage the ozone layer and has no other negative effects.