Cooling and Heating Cycles of the Window Air Conditioners
The figure above shows all the parts of the window air conditioner namely, the compressor, condenser, the expansion valve (capillary) and the evaporator. What is different in this air conditioner from the other types of air conditioners is the 4-way reversing valve incorporated within the refrigeration cycle. The reversing valve is the four position valve with four ports. In the figure the air cooling cycle is shown by the dotted line, while the air heating cycle is shown by the continuous line.
In the normal course of running in the summer seasons, when the air conditioner works as the cooler, the indoor unit acts as the evaporator or the cooling coil and outdoor unit acts as the condenser. Due to this the cooling effect is produced inside the room, while the heat is rejected to the atmosphere.
In the winters, when the atmospheric temperature is too low, the position of the reversing valve is changed and the machine works as the heat pump. The indoor unit becomes the condenser and the outdoor unit becomes the evaporator. The outdoor unit absorbs the heat from the atmosphere and releases it inside the room via the condenser to produce the heating effect. The reversing valve changes the direction of the flow of the refrigerant and plays the vital role between the air conditioner and heat pump.
This method of reverse valve can work in the atmospheres where the external temperature during the winter season is around 3 to 4 degree C. If the atmospheric temperature is below this, the frost will be formed on the surface of the evaporator and its working will be hampered. For effective heat transfer in low temperatures, the frost should be removed from the evaporator at regular intervals. In places where there is extremely low temperature, the defrost system can be employed to remove the frost from evaporator automatically. Even the reversing valve can be operated automatically by using the solenoid valve and operating it with the switch.