Refrigeration is actually a fairly straight forward easy to understand process....
Refrigeration is actually a fairly straight forward easy to understand process. Although there are several ways that refrigeration can be achieved in a system, the most common is vapor compression, in which the compressor is the heart of the system. The temperature of the refrigerant is related to its pressure. For example R134 is roughly -15 degrees Fahrenheit at no pressure. (Thats gauge pressure and not absolute). When compressed to 250 psi R134 is about 148 degrees.
Starting from the compressor, the refrigerant vapor is compressed. In the process it will heat up hotter than the surrounding air. As the refrigerant passes through the condenser, heat is given off since it is hotter than the surrounding air and as a result it condense and turns liquid.(thats why it is called a condenser). The liquid refrigerant then passes through an expansion valve or a capillary tube where it turns into low pressure liquid and as it passes through the evaporator absorbs heat from its surrounding since it is much colder. This makes the refrigerant turn into gas and evaporates (again it is why it is called the evaporator) absorbing tremendous amount of heat. Then refrigerant vapor passes through the accumulator in which moisture accumulates ( why it is called the accumulator) before it is sucked into the compressor to be compressed again. (Why do you think the compressor is called compressor? you know the answer by now)
The whole system is really a means for heat transfer for removing heat from one place and expelling it outside in which the refrigerant is the vehicle. Heat always travel from hot to cold. If something is hotter than the surrounding, it gives off heat and if it is colder, it absorbs heat. Simple as that. There is a thing called latent heat of vaporization or in thermodynamic term it is called enthalpy of vaporization. This simply means when liquid reach its boiling temperature at a constant pressure it will no longer get any hotter. . For example when you boil water at sea level it stay 212 degrees no matter how much heat you put under the pot. You can also think of it as putting heat into it but it is not doing anymore work. since the water is not getting any hotter. If there was meat in there it would not get soft any faster by adding more heat. The water will just absorb all that heat without getting any hotter. That is just one of those wierd law in physics and it is the underlying principle in theory of refrigeration. It is the fact that when liquid evaporates, it absorbs tremendous amount of heat and carries it away. Rub alcohol on your skin and the skin feels cold as the alcohol evaporates. Thats a simple form of refrigeration at its very basic.
There are other types of refrigeration for example another one is called "absorption system". This kind uses heat to vaporize liquid (usually ammonia and water solution) mixed in an absorbing material. as the subtance evaporates it accumulates on the other end as liquid. When heat is taken away, the whole thing cools down and the pressure drops to a point so that the liquid that has accumulated will evaporate and be collected back on the absorbing material. This produce refrigeration. It has no moving parts no compressor and just uses heat. In fact it can be used as ice maker which is ironic since it works by heat. The last one would be thermoelectric. If current is passed through two dissimilar metals one of the metal will get cold at the junction, and it is called the peltier effect. Coolers that plugs into cigarrete lighter are example of these type of device. They are not really very efficient but have some advantages such as it can be used as food warmer when the current is reversed.
on Jul 10, 2010 | Air Conditioners