In an ammonia absorption refrigeration system, liquid ammonia's properties, including its high latent heat of vaporization and relatively low boiling point, are crucial for the system's operation, enabling cooling in the evaporator, condensation in the condenser, and regeneration in the generator.
Here's a breakdown of how these properties are utilized:
Latent Heat of Vaporization:
Ammonia has a high latent heat of vaporization, meaning it absorbs a significant amount of heat when it transitions from liquid to gas (evaporates). This heat is drawn from the surroundings, causing the cooling effect in the evaporator.
Boiling Point:
Ammonia's boiling point is relatively low (around -33.3°C at atmospheric pressure), allowing for refrigeration at temperatures below 0°C without requiring pressures below atmospheric in the evaporator.
Absorption Refrigeration Cycle:
Evaporator: Liquid ammonia, at a low pressure and temperature, evaporates in the evaporator, absorbing heat from the surrounding area (e.g., inside a refrigerator).
Condenser: The ammonia vapor is then compressed and passed through a condenser, where it releases heat and condenses back into a liquid state.
Generator: In an absorption system, a weak solution of ammonia in water is pumped to a generator where it is heated, causing the ammonia to vaporize and separate from the water.
Absorber: The ammonia vapor is then absorbed in the absorber by water, forming a strong solution of ammonia in water.
Expansion Valve: The high-pressure liquid ammonia is then throttled through an expansion valve, reducing its pressure and temperature, and it is ready to enter the evaporator again.
