Working principle of refrigeration cycle

Working principle of the refrigeration cycle

Process 1-2:(Constant pressure process)(Evaporation process):

• In this process, low pressure & low enthalpy liquid refrigerant enters the evaporator.
• The evaporator is a heat exchanger either fin & tube or shell & tube type.
• Refrigerant passes through the tube and over the tubes,the room air flows.
• Refrigerant absorbs heat from the room air and thus cools the room air
• At the outlet of the evaporator, we have saturated refrigerant vapour.

Process 2-3(Compression process)(Isentropic process):

• In this process, saturated vapour refrigerant coming from the evaporator is mechanically compressed from p2 to p3.
• P3 is also known as setpoint is so selected that, the temperature corresponds to this pressure is above ambient temperature.
• The refrigerant compressor required external work in the term of electrical energy and this cycle is inclining with the 2nd law of thermodynamics.

Process 3-4(Constant pressure process)(Condensation process):

• High temperature and high-pressure vapour refrigeration coming from the compressor enter into the condenser is also a heat exchanger placed near the ambient air.
• Heat transfer takes place between the ambient air and the refrigerant vapour.
• Refrigerant vapour gives away latent heat and gets converted into hot liquid refrigerant at the outlet of the condenser.

Process 4-1(Expansion process)(Isentropic process):

• In this process, hot liquid refrigerant passes through the expansion device.
• Expansion device consists of a small aperture/capillary, leading to pressure drop at constant enthalpy.
• Due to change in pressure from p4 to p1, the refrigerant is again available for reuse to carrying cycle 1-2-3-4-1.

Superheating & Subcooling:

• Liquids are practically incompressible. Hence pressure of liquid may damage the compressor.
• In order to avoid the liquid refrigerant from entering into the compressor, superheating is done.
• Refrigerant is slightly heated before it enters the compressor.
• Similarly, the presence of gas passing through the expansion device reduced the efficiency of the expansion valve.
• Hence refrigerant is further slightly cooled before it enters the expansion valve.

Note:

We can use the cycle without accessories also, but for safety purpose we can use accessories.

Accessories  are,

Oil separator:

• It is fitted between the compressor and condenser.
• It helps to remove oil from refrigerant and it passes only vapour refrigerant to condenser and it sent back liquid refrigerant to the compressor.

        Liquid receiver:

• It is fitted between condenser and filter.
• It helps liquid refrigerant to pass forward.

Accumulator:

• It is fitted between the evaporator and compressor.
• It ensures that the refrigerant leaves the accumulator as a vapour and not a liquid state for the compressor to induce.