From where in the refrigerator the cold undertakes?
Each of us daily use tens of cunning arranged machinery and appliances: here to you both an ordinary alarm clock, and the microwave oven, and the computer, and the car and still a set of the most ill-matched electronic and mechanical brotherhood without which our life, apparently, is already inconceivable. But reflect whether much we know about these silent assistants (about an alarm clock of it you will not tell) as they are arranged how work? Yes anything! Works - and it is fine behind what once again to strain crinkles!
In my opinion, it is very sad that behind daily vanity and the ordinary of a civilization, we ceased to notice surprising, and at times just ingenious device of some habitual things. Of course, to try to understand the principle of operation of the computer or even the ordinary calculator - it is senseless (the calculator cannot be understood, it is only possible to believe in him), but to here master the refrigerator device quite on forces to everyone.
I will begin with the theory. The refrigerator is entirely obliged by the emergence to science thermodynamics which, apparently from the name, is engaged in transformation and movement of thermal energy, that is is warm. It also occurs in the refrigerator: heat which is in the refrigerator, “ it is taken “ also it is taken out outside, cooling its (refrigerator) contents. Intermediaries in transportation of heat are coolants, they capture internal heat, take out it outside, give, and then empty come back to a refrigerator belly anew to repeat this process.
Coolant (reduction from the words “ refrigerating agent “) it is accepted to call working substance with a low temperature of boiling (evaporation). As coolant a long time used freon - 12 (R - 12) which production was organized in 1931, but in 1980 adverse effect of atomic chlorine on ozone in the atmosphere - production and filling of refrigerators with freon was open - 12 began to decline. Today as coolants use R - 134a (the descendant of freon - 12), dimethyl air, propane, butane, isobutane and their mixes - all these substances in quantity in which they are used in refrigerators, are absolutely harmless to the person and environment.
As it was told, the love of refrigerators to coolants is connected with the low temperature of boiling of the last: propane boils at -42,1 °C, butane - at -0,5 °C, isobutane - at -11,7 °C. But how it allows to keep low temperature in the refrigerator? For the answer to this question we will address physics: it is known that during the boiling and evaporation of substance take away heat from environment, that is, cool it (the feeling of a cool from grinding is connected with it, for example, alcohol - alcohol evaporates, taking away heat from a body), therefore, to cool, for example, a beer jar, it it is necessary “ to pour “ some easily beginning to boil liquid which, having begun to boil, would select heat at beer.
Therefore to give to the refrigerator the chance to freeze, it is necessary to fill some of its parts with coolants which easily would boil, having cooled these parts, and, therefore, having cooled also contents of the refrigerator. Propane approaches as nobody else here: if it boils already at -42, then it will be very simple to create conditions for its boiling at the room temperature in the refrigerator.
Finishing, thus, theoretical part, I will tell that coolants are chosen as the main working substance in refrigerators only thanks to the low temperature of boiling, and, as a result, it is easy for ability to incorporate warmly.
We will pass directly to refrigerators. Any refrigerator consists of three bodies: the compressor (the motor which constantly rustles), the condenser (a black metal coil on the back panel of the refrigerator) and the evaporator (metal “ box “ who is usually visible in the freezer).
If you understood that I there so long wrote about coolants, then the principle of operation of the refrigerator will reach you quickly.
The coolant liquefied under big pressure on the soaking-up pipeline from the condenser (coil) comes to the evaporator (“ box “) . From - for low pressure in the evaporator and the low temperature of boiling of coolant, it (coolant) begins to boil and evaporate intensively, cooling the only thing what contacts to - metal walls of the evaporator, the evaporator, in turn, cools air in the refrigerator. Vapors of coolant are pumped out by the compressor which, by the way, and creates low pressure in the evaporator, to the place of the evaporated coolant new liquefied downloads.
The gaseous coolant which is pumped out from the evaporator passes through the compressor from which already in the squeezed state comes to the condenser (coil). At sharp tightening any gas heats up therefore tubes at the exit from the compressor during its work and a coil on a back wall of the refrigerator always hot (warm). In process of passing on a coil the compressed hot gaseous coolant gradually cools down and passes into a liquid phase, and already in a liquid phase it comes back to the evaporator where this process begins anew. This circulation lasts until temperature sensor in the refrigerator does not give a signal to the compressor to stop - coolant in the evaporator will evaporate, and new will not arrive any more, therefore, cooling will stop.
If you did not fall asleep yet, you can have a question: why already liquefied coolant does not begin to boil directly in a coil, temperature in it room, and isobutane boils already at -11 °C. Let`s address physics again: it is known that the pressure is higher, the boiling temperature is higher. I will explain on a concrete example: all are for some reason sure that water boils at 100 °C, and you know that, for example, in the boiler at combined heat and power plant water boils at a temperature of 200 °C, and at the height of 7130 m (Lenin Peak on Pamir) it begins to boil at 70 °C (it is impossible to cook meat in such conditions). All this occurs from - for different pressure: in a copper it huge - boiling temperature high, in mountains low - temperature of boiling is also low. Absolutely the same occurs also in the refrigerator: isobutane cannot begin to boil in a coil from - for a high pressure (temperature of boiling increased), in the evaporator it boils easily as pressure in it low.
Including therefore you should not think that the refrigerator cannot be cooled up to the temperature below temperature of boiling of coolant. For this purpose it is enough to lower pressure in the evaporator, and the same isobutane will begin to boil not at -11 °C any more, and at -20 °C or at -40 °C.
I will sum up told. The compressor is some kind of pump which pumps over coolant, creates a high pressure in a coil and low pressure in the evaporator that respectively promotes liquefaction and evaporation of coolant. The evaporator is a source of cold, in is mute under low pressure coolant boils and evaporates, cooling environment. In the condenser (coil) there is a cooling and liquefaction with the compressed compressor and therefore hot, coolant.
I hope, I managed to explain the refrigerator device popularly.