Refrigeration Cycle

Refrigeration Cycle 

Youtube Link -

Video on the refrigeration cycle

Basic Refrigeration Cycle 

It is the base of the refrigeration system. Each and every Air-conditioner runs on this principle irrespective of location.

It used fluid called refrigerant to transfer and absorb heat.

In the condenser , heat is removed and in the evaporator, heat is absorbed.

Main Component 

1.Compressor

-The compressor is the heart of the refrigeration cycle.

-The compressor pumps vapor refrigerant at high pressure and temperature into a condenser, and receive superheat vapor at low temperature and pressure from the evaporator. 

-Types of Compressor

a) Reciprocating.

b) Scroll.

c) Screw.

d) Rotary.

e) Centrifugal

2.Condensor

-It is part of refrigeration system and responsible for heat transfer.

-It receives vapor refrigerant from the compressor at high temperature and pressure and removes its heat and passes it to the expansion valve.

-Types of Condenser

    a)air-cooled condensers

    b)water-cooled condensers 

    c) evaporative condensers. 

3.Expansion Valve

-It controls the refrigerant into the refrigeration cycle. It receives the refrigerant from the condenser(high-pressure liquid) and it reduces the pressure and passes it to the evaporator.

-The liquid refrigerant is controlled according to the superheat at the outlet of the evaporator.

-It allows the refrigerant in such a way that the refrigerant coming out from the evaporator will be in vapor form.

-Types of Expansion Valve

Automatic Exp. Valves

Thermostatic Exp. Valves

Capillary Tubes

Float Valves

4.Evaporator 

-It is part of the refrigeration cycle and responsible for heat transfer.

-It receives refrigerant from the TXV valve or capillary tube and this refrigerant is in liquid and vapor form at low pressure.

-It changes the phase of refrigerant in to complete vapor form and supplies to the compressor.

-Types of  Evaporator

a) Bare Tube Evaporators

b)Plate Type of Evaporators

c) Finned Evaporators

d)Shell and Tube types of Evaporators

Process

a. 1-2 compression

-In this process Compressore receive refrigerant from the evaporator in gas form 

-After receiving refrigerant in gaseous form, the compressor compresses the refrigerant to high pressure.

-Temperature and pressure both will be high when refrigerant comes out from the compressor.

b.2-3 heat removal

-High pressure, high-temperature refrigerant (Vapour for) enter into the condenser coil.

-Heat is removed from the refrigerant.

-The refrigerant phase is changed from vapor to liquid.

c. 3-4 Expansion

-It is a metering part of the refrigeration cycle.

-It reduces the pressure of the refrigerant.

-It uses a Bob which is placed on the evaporator coil 

It senses the temperature and adjusts the pressure reduction.

It reduces the pressure in such a way that refrigerant coming out from the evaporator should be in vapor form.

d. 4-1 Heat Addition 

-Low-pressure liquid enters into the evaporator from the expansion device.

-In this section, heat is added to refrigerant by a fan, and refrigerant starts converting from liquid to low-pressure vapor.

-and then low-pressure vapor refrigerant enters into compressor and cycle runs again.

Temperature and pressure depend on refrigerant.

Every refrigerant has different freezing and boiling properties.

Refrigeration Cycle with Accessories

       

Credit-Dryall for picture

The component is part of a system without which the system can not run.

The system can run without accessories also 

but we use accessories to enhance the efficiency and safety of the system.

Basic Accessories used for the system are .....

1.Filter drier 

-It removes impurity such as dirt, metal chip from the refrigerant.

-It removes moisture, acid from the refrigerant.

-Mostly it is used in Liquid line but in the market both types of drier available i.e. liquid line and suction line.

2.Liquid Reciever

-It is a vessel where we store refrigerant.

-It is installed on the outlet of the condenser.

-It is used to ensure the complete conversion of refrigerant from vapor to liquid.

-It is a helpful part when the system required servicing or part replacement.

3.Oil Separator

-It is used on a system where it is difficult for oil to return from the evaporator.

-Compressor having moving parts, to avoid wear and tear we use compressor oil. Some times with refrigerant this oil also comes out from compressor. And when this oil comes in contact with moisture it forms acid and this acid affects the life of other components.

-It is installed just after the compressor.

-High pressure, high-temperature refrigerant from compressor enter into oil separator.

-Oil settles down at the bottom and vapor refrigerant moves out from oil separator.

4.Sight Glass

To check the phase of refrigerant, we use sight glass.

5. Suction Line Accumulator

-Compressors are designed to compress vapor only. liquid refrigerant can damage the compressor and it affects the efficiency, life of the compressor.

-To avoid entering liquid refrigerant to compressor we use the accumulator before the compressor.

-Accumulators have a metering ejector device that picks up liquid, vaporizes it, and returns it to the compressor. This prevents liquid slugging and controls oil return. It is particularly important on hot gas to defrost systems, heat pumps, etc., where surges of liquid refrigerant frequently go back down the suction line.

-Vertical accumulators use a U-tube or tube-within-a-tube design to draw gaseous refrigerant off the top of the vessel. At the bottom of the U-tube, an orifice picks up a small amount of oil and liquid refrigerant and meters it back with the gaseous refrigerant. The small amount of liquid refrigerant will boil off in the suction line. The oil will be carried with the gaseous refrigerant back to the compressors.

6. Solenoid Valve

-A solenoid valve is an electromechanical valve frequently used to control the flow of liquid or gas.

-Their function is simply to turn refrigerant flow on and off.

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