Vapour Absorption Refrigeration System

Overview

• The vapour absorption refrigeration system is similar to the vapour compression system but uses an absorber instead of a compressor.
• Uses an ammonia-water solution where ammonia acts as the refrigerant and water as the absorbent due to its strong affinity for ammonia.

Components of the System

1. Evaporator
   • The site of the refrigeration effect.
   • Low-pressure, cold liquid ammonia absorbs heat and turns into vapour.
2. Absorber
   • Contains a weak ammonia-water solution.
   • Absorbs ammonia vapour from the evaporator, forming a strong solution.
   • Heat is liberated during absorption, requiring cooling water to maintain absorption capacity.
3. Pump
   • Transfers the strong ammonia-water solution from the absorber to the generator.
4. Generator
   • Heat is applied to boil off ammonia from the solution.
   • Ammonia vapour is separated using an analyzer.
   • Remaining weak solution returns to the absorber via a pressure reducing valve.
5. Analyzer
   • Located on top of the generator.
   • Ensures only ammonia vapour passes through, while water vapour is condensed and returned.
6. Condenser
   • Cools high-pressure, high-temperature ammonia vapour into liquid.
   • Can be water-cooled or air-cooled.
7. Expansion Valve
   • Expands the liquid ammonia, reducing its pressure and temperature.
   • Produces cold, low-pressure liquid ammonia for recirculating to the evaporator.

Working Procedure

1. Evaporation
   • Cold liquid ammonia absorbs heat in the evaporator, turns into vapour.
   • Low-pressure ammonia vapour moves to the absorber.
2. Absorption
   • Ammonia vapour absorbed by water in the absorber.
   • Heat is removed by cooling water, maintaining absorption efficiency.
3. Pumping
   • Strong ammonia-water solution pumped to the generator.
4. Generation
   • Heat applied to separate ammonia vapour.
   • Analyzer ensures only ammonia vapour passes through.
5. Condensation
   • Ammonia vapour condensed into liquid in the condenser.
6. Expansion
   • High-pressure liquid ammonia expanded to low-pressure liquid.
   • Cold liquid returns to the evaporator to continue the cycle.

Cycle Continuation

• The cycle repeats, continuously providing cooling or refrigeration in the evaporator area.

Conclusion

• The vapour absorption refrigeration system effectively substitutes the compressor with an absorber and pump, relying on an ammonia-water solution for refrigeration.

Additional Information

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