Lithium bromide – water absorption refrigeration system
- Lithium bromide – water systems are used extensively in air conditioning and other high temperature applications.
- This system uses a solution of lithium bromide (Li.-Br.) in water, where the water itself used as a refrigerant and Li.-Br. is used as a absorbent.
- The lithium bromide solution has a strong affinity for water vapor but it is corrosive in nature. Therefore inhibitors should be added to protect the metal parts of the system.
- Therefore the common refrigerant, absorbent and inhibitors are:
Absorbent: Lithium bromide solution
Inhibitor: Lithium chromate solution
- Lithium bromide – water vapor absorption refrigeration system:
– The absorber and the evaporator are placed in one shell, operate at the low pressure of the system.
– The generator and the condenser are placed in another shell, operate at high pressure of the system.
- The water to be chilled is passed through the chilled- water tubes in the evaporator.
- The water refrigerant evaporates because of low evaporator pressure. The water vapors thus formed will be absorbed by the strong lithium bromide solution. This solution maintains a low pressure in the evaporator and the solution becomes weak.
- This weak solution is pumped by a pump to the generator. In the generator, it is heated up by using steam or hot water in the heating coils.
- The heat evaporates a portion of water and the solution becomes stronger. Thus strong solution is passed through the heat exchanger and the sprayed in the absorber. The weak solution of lithium bromide from the absorber to the generator is also passed through the heat exchanger. This weak solution gets heat from the strong solution in the heat exchanger. This reduces the quantity of steam required to heat the weak solution in the generator.
- The refrigerant water vapors formed in the generator are passed to the condenser. They are cooled and condensed by the cooling water flowing through the condenser water tubes.
- The cooling water for condensing is pumped from the cooling water pond of cooling tower. The cooling water first enters the absorber. It takes away the heat of condensation and dilution. The condensate from the condenser is supplied to the evaporator to compensate the water vapor formed in the evaporator.
- The pressure – reducing valve reduces the pressure of condensate from the condenser pressure to the evaporator pressure. The cooled water from the evaporator is pumped and sprayed in the evaporator to cool the water. The cooled water is passed through the chilled tubes for air conditioning. This completes the cycle.