2006-06-26 11:55:37 · 3 answers · asked by Stuart D 1 in Science & Mathematics ➔ Engineering
Basically, heat is absorbed from the hot room by a refrigerant liquid which expands into a gas. When things expand, they absorb heat, so this cools the room. The gas then goes to a compressor, which squishes it back into a liquid. It only has to increase the pressure (the temperature goes up too), and send it to a set of coils outside. The room heat, plus the heat from the compressor is lost to the atmosphere. You then have a cool liquid to send back to the room coils.
ok. You've moved a lot of heat around, but you only had to do a bit of compression and pumping. You put in a little work, and got a lot of cooling out of it. We have a measure of this, called the coefficient of performance, or COP. In this case 3500/1500 is about a 2.3, which isn't all that great. 3500/800 is about 4, which is a little better. Try for more like 5 to 7.
A more thorough explanation would require some thermodynamic charts. You might want to look up the air conditioning cycle using your favorite search engine. It will take a bit to understand the whole thing. If you are really interested in this, I would recommend a nice four year course in engineering.
2006-06-26 18:16:16 · answer #1 · answered by drslowpoke 5 · 0⤊ 0⤋
Those thermodynamics classes were a long time ago, but here's what I remember: Refrigerators and air conditioners are examples of heat pumps. They transfer heat from a colder place to a warmer one. They are moving, not creating heat, so the amount of energy required is only the entropy involved, not the the energy moved. The apparent thermal efficiency can appear to be more than unity if you consider only one end of the device.
A ton of ice just absorbs heat, so its energy change is the 3516.8 W. The heat that the refrigerator removes is available elsewhere, so the net energy change is less.
2006-06-26 15:35:44 · answer #2 · answered by injanier 7 · 0⤊ 0⤋
If I am reading the book right, its down to definitions. Its because a ton of refrigeration is a cooling measure and the W of electricity is a mechanical measurement (due to generators) and the two units are not well defined for all variables
2006-06-26 12:03:34 · answer #3 · answered by Brian 3 · 0⤊ 0⤋