Mechanical refrigeration is accomplished by continuously circulating evaporating and condensing a fixed supply of refrigerant in a closed system. Evaporation occurs as a low temperature and low pressure while condensation occurs at high temperature and pressure. Thus, it is possible to transfer heat from an area of low temperature (i.e. refrigerator cabinet) to an area of high temperature (i.e. kitchen).
There are many components that go into an air conditioning system. However, to achieve a basic understanding we will only make reference to the most essential components as these are the underlying parts that make the system work and transfer heat throughout the system.
The system consists of the evaporator, compressor, condenser, and metering device. The four primary elements are found in every refrigeration system and are used in the cycling process of removing heat and transferring that heat from one location to another.
Beginning the cycle, the evaporator the low pressure liquid expands, absorbs heat and evaporates, changing the to a low pressure gas at the evaporator outlet. The unit compressor pumps this gas from the evaporator to the accumulator (which ensures that no un-evaporated liquid reaches that compressor causing compressor damage). The compressor then condenses the gas by compressing it and low temperature high pressure gas that is transferred though the line to the condenser side of the system.
When the gas gets to the condenser it is then a high pressure high temperature gas. The condenser heat is removed from the gas (using fans) which then condenses and becomes a high pressure liquid. In some instances the high pressure liquid drains from the condenser into a liquid storage or receiver tank.
Between the condenser and the evaporator is a metering device. This device is a valve or small fixed size tubing or orifice that meters liquid refrigerant into the evaporator. An air conditioning system cycles and runs this process many times to remove heat from the house or to bring heat into the home depending on what time of year it is and what the system has been set to do.
Eventually the desired air temperature is reached and the thermostat or cold control will break will the electrical circuit to the compressor motor and the compressor. As the temperature of the air through the evaporator raised, the thermostat or cold control remakes the electrical circuit. The compressor starts, and the cycle continues.
Of course there are many other components involved in this process and it is more complex than this. But basic refrigeration boils down to the transfer of heat from one location to another. It is the ability to manipulate refrigerant that picks up heat and absorbs the heat. The heat is then carefully controlled and released out of the system achieving a desired heating and cooling effect whether in a home or a refrigerator the process is similar.