Subject : Refrigeration and Air Conditioning

Topic : Vapour Absorption Refrigeration

Difficulty : Medium

Steam jet or Ejector refrigeration system uses water as refrigerant. It uses the basic principle of boiling of liquid at lower temperature by reducing pressure on its surface.

This system employs a steam ejector or booster instead of mechanical compressor. The main components as shown in figure are flash chamber or evaporator, steam nozzles, ejector and condenser.

The flash chamber is heavily insulated and is fitted with perforated pipes which spray warm water coming out of refrigerated space. Some of this water is converted into vapours after absorbing latent heat from the rest of the water, thereby cooling it. Loss of water through vapours is made up from make-up water line.

High pressure steam from boiler is passed through steam nozzle thereby increasing its velocity. This entrains water vapours from flash chamber and results in further formation of vapours.

The mixture of steam and water vapour passes through venturi-tube of ejector and gets compressed. This leads to rise in temperature and pressure of the mixture and then it is fed to the water cooled condenser.

The condensate is again fed to boiler as feed water.

Steam jet refrigeration system is widely used in paper mills, breweries, food processing plants, gas plants etc. Since water is the refrigerant, it cannot be used for applications below 0°C.