As an HVAC engineer explain refrigeration cycle step by step in the simplest words?

Refrigeration cycle basically is a thermodynamiccycle utlizing the temperature-pressure relashiship for rrefrigerants which those relashions are visible at low temperatures.

1. condensation in the condinser: refrigerant at high temperature and pressure enters the condenser and heat is being rejected to either air or water to result in a high pressure liquid refrigerant.

2. expanssion via the expanssion valve: expanding the high pressure liquid refrigerant results in dropping the pressure which drops the temperature of the refrigerant further.

3. Evaporation in the evaporator: cold liquid refrigerant absorbs the heat from the cooling media (air or water) which results in vaporizing the refrigerant.

4. Compression via the compressor: vaporized refrigerant get compressed in the compressor to high pressure/temperature vapor rifrigerant which feeds the condinser.

The cycle repeats.

There are additional components that are added to this cycle to improve the system performance such as:

• Reciever/economizer: stores extra high pressure liquid refrigerant to be used when additional load is required, needed when the compressor uses capacity valves to control amount of circulated refrigerant.
• Knockout drum/liquid traps: used after the evaporator to make sure no liquid get sent to the compressor. It's function is to collect the liquid and either boil it through a heater or resend it to the evapoator.
• Oil Separator: used whith systems that use compressors that need oil circlation like screw compressors. Such systems mix the oil and refrigerant and would need a system to separate them again before the refrigerant is sent to the condenser. Some oil travel through the system and is called carried over oil, it'll collect in the evaporator and would reduce the heat transfer efficiency. Oil still is needed in this case to collect the oil in the evaporator and send it bach to the compressor.

expansion valve to evaporator to comperssor to condensor simple cycle

This system is called Direct expansion system(DX Type). refer below the details.

A. Compressor : The cold saturated vapor refrigerant is convert to high pressure & temperature refrigerant.(like gas form, Entropy constant)

B. Condensing unit : The high pressure and high temperature refrigerant is convert to high pressure & low temperature liquid refigerant.(heat removing process,pressure constant).

c. Expansion device : It convert the high pressure & low temperature liquid refigerant into low pressure & low temperature liquid refrigerant.(Enthalpy constant)

D. Evaporator : It convert the low pressure & low temperature liquid refrigerant into vapour stage refrigerant.(heat absorbing process- like partial liquid & gas form, Pressure & temperature constant)

A refrigeration cycle process done through four equipments using a low boiling point refrigerant. 

1. Compressor - Pressure Increaser

increase the pressure of refrigerant to condenser (low pressure vapour to high pressure vapour) which coming from evaporator

2. Condenser - Heat Exchanger

Condense the the vapour state refrigerant in to liquid state through a medium ( Air, Liquid etc..) heat loss in condenser

3. Expansion Valve - Pressure Reducer

Reduce the pressure of liquid state refrigerant through a throttle valve ( High pressure liquid to low pressure liquid)

4. Evaporator - Heat Exchanger

Absorb heat and change the state of refrigerant from  liquid to vapour by heat gain in evaporator

these4 process will be done continuously in a cyclic process is known as refrigeration cycle

Principles of Refrigeration

• Liquids absorb heat when changed from liquid to gas 

• Gases give off heat when changed from gas to liquid. 

For an air conditioning system to operate with economy, the refrigerant must be used repeatedly. For this reason, all air conditioners use the same cycle of compression, condensation, expansion, and evaporation in a closed circuit. The same refrigerant is used to move the heat from one area, to cool this area, and to expel this heat in another area. 

• The refrigerant comes into the compressor as a low-pressure gas, it is compressed and then moves out of the compressor as a high-pressure gas.

• The gas then flows to the condenser. Here the gas condenses to a liquid, and gives off its heat to the outside air. 

• The liquid then moves to the expansion valve under high pressure. This valve restricts the flow of the fluid, and lowers its pressure as it leaves the expansion valve. 

• The low-pressure liquid then moves to the evaporator, where heat from the inside air is absorbed and changes it from a liquid to a gas.

• As a hot low-pressure gas, the refrigerant moves to the compressor where the entire cycle is repeated. 

Note that the four-part cycle is divided at the center into a high side and a low side This refers to the pressures of the refrigerant in each side of the system

The fluid is driven around the cycle by the compressor, which compresses the low temperature, low pressure vapor leaving the evaporator to high pressure, high temperature vapor.

That vapor is condensed to liquid in the condenser, thus giving off heat at a high temperature to the surrounding environment.

Finally, the high pressure, high temperature liquid leaving the condenser is cooled and reduced in pressure by passing it through an expansion valve. This provides the input to the evaporator which was the first step of the cycle.

There are four general steps

1.Use the compressor that compress the gas high temperature &pressure.

2.And then compressed gas send to condenser that convert into fluid

3.After that use the expansion valve that reduce the temperature &pressure of fluid.

4.At the end send the fluid to evaporater that convert fluid into vapor form and again this vapor send to compressor

in the compreesion cycle the refrigrant enter the compressor in compress there to the condenesor and change from vaopr to fluid and then move to expansion valve which reduce its pressure to the pressure of the evaportor

the cooling effect happen in the evaportor

when we give electrical power to compressor we are given to refrigerant fluid work it will change the stage from saturation Gas to super heated gas and in next stage we need released temperature the stage of gas it will change direct to liquid saturation but we need refrigerant full liquid because the specific of rant. fluid boiling at 0 c and in this stage the ref fluid it will be absorption temperature inside Refrigerator from 20 c to less to less as per adjust temperature sensor inside Refrigerator   

• Expansion.
• Evaporation.
• Compression.
• Condensation.

COMPRESSOR-CONDENSER-EXPANSION VALVE-EVAPORATOR.