Working Principle, Function, Types of Evaporators and Accumulator
In refrigeration and air conditioning systems, the evaporator is the component where actual cooling takes place. It absorbs heat from the surroundings and converts liquid refrigerant into vapour. This chapter from the book "Evaporator" explains the working principle, functions, types of evaporators used in different appliances, superheating, and the function and types of accumulator.
Working Principle of Evaporator
The evaporator works on the principle of heat absorption. Low-pressure, low-temperature liquid refrigerant enters the evaporator from the expansion device. As it flows through the evaporator coils, it absorbs heat from the surrounding air or substance.
Due to heat absorption, the refrigerant evaporates and changes into vapour. This vapour is then drawn into the compressor, completing the refrigeration cycle.
Function of Evaporator
- Absorbs heat from the space to be cooled
- Converts liquid refrigerant into vapour
- Maintains required temperature
- Ensures continuous refrigeration cycle
Types of Evaporators Used in Different Systems
1. Domestic Refrigerator
- Plate Type Evaporator: Flat surface, used in freezer section
- Finned Type Evaporator: Used in frost-free refrigerators with fan
2. Water Cooler
- Coil Type Evaporator: Immersed in water tank
- Provides direct cooling to water
3. Bottle Cooler
- Plate or Coil Type Evaporator: Surrounds storage space
- Ensures uniform cooling of bottles
4. Window Air Conditioner
- Finned Tube Evaporator: With blower for air circulation
- Provides rapid cooling of room air
5. Split Air Conditioner
- Finned Tube Evaporator: Located in indoor unit
- Uses fan to circulate cooled air
Superheating in Evaporator
Superheating is the process in which the refrigerant vapour is heated above its saturation temperature after complete evaporation.
Importance of Superheating
- Ensures no liquid refrigerant enters the compressor
- Protects compressor from damage
- Improves system efficiency
Accumulator
Definition
An accumulator is a protective device installed in the suction line between the evaporator and compressor. It prevents liquid refrigerant from entering the compressor.
Function of Accumulator
- Separates liquid refrigerant from vapour
- Prevents liquid entry into compressor
- Ensures only vapour refrigerant enters compressor
- Improves compressor safety and life
Working
The refrigerant from the evaporator enters the accumulator. Liquid refrigerant settles at the bottom, while vapour rises and moves to the compressor. The liquid refrigerant gradually evaporates and joins the vapour flow.
Types of Accumulator
- Suction Line Accumulator: Commonly used in refrigeration systems
- Oil Return Type Accumulator: Helps return oil to compressor
Conclusion
The evaporator is the main component responsible for cooling in refrigeration systems. Different types of evaporators are used based on application requirements such as refrigerators, water coolers, and air conditioners.
Superheating ensures safe operation, while the accumulator protects the compressor from liquid damage. Understanding these concepts helps RAC students in proper system operation, maintenance, and troubleshooting.