does any one know how a freezer works? how about an ac?

Question

what makes it cold?

Answer 1

The cooling happens because of a process called Adiabatic Expansion of a gas. If a gas is suddenly expanded in volume, like when it is forced out of a narrow nozzle, it's temperature drops.

The problem is, for the cooling to continue, you need to make the gas expand again and again. This means you will need to compress the gas in between. Now compressing a gas increases the temperature, so what do you do ? In the freezer (or AC), the gas expansion happens inside the chamber we want to cool and the compression happens outside that chamber !!!! The hot compressed gas is allowed to cool down to near room temperature through those radiator tubes you see at the back of the freezer.

So, a compressor compresses a gas making it hot. The hot gas cools down to room temperature outside the cooling chamber by the heat radiator tubes and then it is made to expand through a narrow orifice inside the chamber being cooled to lower it's temperature.

Answer 2

The principle is that When Freon changes from a liquid to a gas its temperature drops. A lot. And vice versa.

You have two "sides" to a freezer/AC, the high pressure side and the low pressure side, and a presurizing pump between them on one side and a tiny metering orifice on the other.

The pump presurizes the freon. Because of the presurization, the freon gets hot, maybe rises 80 degrees or so. So it is then cooled through a radiator, the part of the AC outside your house or those coils on the back of a fridge. They take all that heat out of the presurized freon.

So after the radiator cools it down, you then have high pressure freon that is at about ambient temperature, and is liquidy.

The freon then travels along a high pressure line to inside the house (or inside the ice box) and it comes to a very tiny orifice, where it is allowed to pass through (an orifice is just an obstruction in the hose with a very tiny hole through it). It enters the orifice under high pressure and at about room temp, then emerges from the orifice into the low pressure side. As it does so, the freon expands in the lower pressure tube and becomes a gas again, in the process its temperature drops by about 80 degrees. This cools the tubes which cools the air around it.

Its a little hard to follow at first but I can summarize for you:

Basically, an expanding gas gets cold, a compressed gas gets hot.

1. presurize the gas outside the house
2. remove the excess heat caused by compression (again, outside the house)
3. expand the gas inside the house
4. use the cold thus produced from the expansion to cool the house air.

I hope that helps.

Answer 3

Freezers and air conditioners are both heat exchangers. They both contain a coil filled with some sort of refrigerant that has air blown over it. That air is cooled by the coil and to lower the temperature of either the house or the interior of the freezer. The refrigerant is changed back into a gas by this interaction, so it then enters a compressor to return it to a liquid state, and the process begins again.

Answer 4

Do you think that the following will be enough info...??

Large, modern refrigeration units use the evaporation principle to produce the low temperatures necessary to do the job required. The process consists of a cycle of compression, cooling and condensation, then the expansion of the liquid, evaporation and re-compression of the vapour.
The Vapour Compression Refrigeration Cycle
The principles used in a vapour compression refrigeration system are: -

A….Compression of a gas causes its temperature to increase. When the gas is cooled and sensible and latent heat removed, the temperature decreases and the gas condenses to liquid which is also the boiling point of the liquid. (The compression also increases the temperature at which the liquid boils). The liquid is then further cooled to around atmospheric temperature.
B….When the liquid is expanded (volume increased) into a lower pressure system, it will boil and cause the liquid temperature to decrease rapidly as it gives up sensible heat to provide the latent heat of partial vaporization of the liquid. The cold liquid and vapour, (the latent heat does not increase the vapour temperature), now pass through the coils inside the ' Cold Box ' (or Evaporator) of the system.

Exchange of heat between the refrigerant and the material or space being cooled, adds more heat to the refrigerant liquid which continues to evaporate. The refrigerant, on leaving the cooling system is now all cool vapour and passes to the suction of the compressor to begin the cycle again.
The sequence of the refrigeration cycle is as follows: -
1…Compression of the refrigerant gas.
2…Cooling and condensation of the refrigerant to liquid.
3…Expansion and partial evaporation of the liquid into a lower pressure which causes cooling.
4…Continued evaporation of the liquid in the 'cold box' - further heating by removal of sensible heat from the item being cooled, to provide the latent heat of vaporization of the refrigerant.
5…Re-compression of the vapour to begin the cycle again.

A/C Unit.

Many modern work places, homes and vehicles, now have Air Conditioning (A/C) Units installed. These operate by having an ‘Air Mover’ (Fan) circulating air through a chamber which contains refrigerated cooling coils.
The actual refrigeration system, (as previously described), is installed OUTSIDE the building or space being cooled. The refrigeration coils are set into the cooling chamber, also outside or in a separate room, through which air from the INSIDE of the space is being drawn by the fan (air mover).
The cooling coils are carrying a refrigerant, that has been expanded across an expansion valve and is being re-vaporised by removing heat from the circulating air passing over the coils and, after cooling by the refrigerant, the air is discharged back into the building.
As the cooled air exchanges heat with the contents of the space, the space and contents cool down, the warmer air then returns to the fan to repeat the cycle.
At the same time, the air gives up much of its moisture (humidity) by condensation on the cooling coils. The condensed water is collected in a drip-tray and disposed of. Working, living and driving conditions are thereby made much more comfortable.

Answer 5

Sme sort of 'working fluid' (usually a Freon-like compound) is compresed. Just like the body of a tire pumb gts warm when used to pump up a tire, the gas gets warm because work has been done on it. Since that gas is now quite a bit hotter than the surrounding air, it can be cooled to 'room temperature' with s simple radiator. Later when the working fluid is allowed to expand, it will try to accept as much thermal energy as possible (to account for the work it is doing as it expands), and this causes the 'cooling' of materials around it. The working fluid is then re-compressed and the cycle repeats.

Doug

Answer 6

Take a look at this website. It is talking about a refrigerator, however a freezer works the same way - just colder.

http://home.howstuffworks.com/refrigerator.htm