Evaporator
In the ITI Refrigeration and Air Conditioning (RAC) trade, the evaporator is a key component of the refrigeration system. The book "Evaporator" provides detailed knowledge about its function, construction, working principle, types, and applications. The evaporator is responsible for absorbing heat from the space to be cooled, making it an essential part of the cooling process.
Introduction to Evaporator
The evaporator is a heat exchanger where the refrigerant absorbs heat from the surrounding medium (air, water, or product) and evaporates from liquid to vapour. It is located after the expansion device in the refrigeration cycle.
Function of Evaporator
- Absorbs heat from the space or substance to be cooled
- Converts low-pressure liquid refrigerant into vapour
- Maintains desired cooling temperature
- Ensures continuous refrigeration cycle
Working Principle
Low-pressure, low-temperature refrigerant enters the evaporator after passing through the expansion device. As it flows through the evaporator coils, it absorbs heat from the surrounding air or substance. This heat causes the refrigerant to evaporate and change into vapour.
The vapour refrigerant then moves to the compressor, completing the refrigeration cycle.
Types of Evaporators
1. Bare Tube Evaporator
- Simple tube design
- Used in small refrigeration systems
2. Plate Type Evaporator
- Flat plate construction
- Used in domestic refrigerators
3. Finned Tube Evaporator
- Tubes with fins to increase surface area
- Used in air conditioners and large systems
4. Shell and Tube Evaporator
- Refrigerant flows inside tubes, water flows in shell
- Used in industrial applications
5. Flooded Evaporator
- Evaporator is filled with liquid refrigerant
- Provides high efficiency
Construction of Evaporator
- Coils or tubes made of copper or aluminium
- Fins for increased heat transfer (in finned type)
- Outer casing or enclosure
- Fan or blower (in forced air systems)
Applications
- Domestic refrigerators
- Air conditioners
- Cold storage systems
- Water coolers
Advantages of Evaporator
- Efficient heat absorption
- Maintains desired cooling temperature
- Simple construction in small systems
- Adaptable to various applications
Common Problems
- Frost formation on coils
- Leakage of refrigerant
- Reduced airflow due to dirt
Remedies
- Regular defrosting
- Cleaning of coils and fins
- Repair of leaks
Conclusion
The evaporator is a vital component that absorbs heat and produces the cooling effect in refrigeration systems. Its proper functioning ensures efficient operation and desired temperature control.
The book "Evaporator" helps RAC students understand its construction, working, and applications, enabling them to maintain and troubleshoot refrigeration systems effectively.