Double stage compression in refrigeration and air conditioning refers to a specific type of compression process used to increase the pressure and temperature of the refrigerant in the system. This process is employed in certain applications where the desired cooling effect cannot be achieved through single-stage compression alone.
In a double stage compression system, the refrigerant is compressed in two separate stages, each with its own compressor. Here's a general overview of how it works:
First stage compression: The low-pressure refrigerant gas enters the first stage compressor, where it is compressed to an intermediate pressure. The temperature and pressure of the refrigerant increase during this stage.
Intermediate cooling: After the first stage compression, the intermediate pressure refrigerant goes through a heat exchanger (intercooler) where it is cooled down before entering the second stage compressor. Cooling the refrigerant helps in reducing the work required for the subsequent compression stages.
Second stage compression: The partially compressed refrigerant from the intercooler enters the second stage compressor, where it undergoes further compression to reach the desired high-pressure level. This stage significantly increases the refrigerant's temperature and pressure.
Condensation and expansion: The high-pressure, high-temperature refrigerant then flows to the condenser, where it releases heat to the surroundings and condenses into a liquid state. The high-pressure liquid refrigerant then passes through an expansion valve, where it undergoes a sudden drop in pressure, leading to a decrease in temperature.
Evaporation and cooling: The low-pressure, low-temperature liquid refrigerant now enters the evaporator, where it absorbs heat from the surrounding air or the space to be cooled. This absorption of heat causes the refrigerant to evaporate and turn back into a low-pressure gas. The cycle then repeats as the gas returns to the first stage compressor.
Double stage compression is often used in large-capacity refrigeration and air conditioning systems to achieve very low temperatures or when there is a need for cooling over a wide range of temperatures. This setup allows for better efficiency and performance, particularly in applications where a single-stage compression system may not be sufficient to meet the cooling requirements.