AIR REMOVAL FROM THE CONDENSER

1 Sources of Air Infiltration in Condenser

1. Air may pass into the condenser with the steam.
2. Air leakage may happen through the packings.
3. The cooling water contains dissolved gases which are released under vacuum.

The amount of air leakage should not be more than 5−15 kg/10000 kg of steam.

2 Effects of Air Infiltration in Condensers

1. The leaked air in the condenser increases the back pressure on the prime mover, and consequently, the thermal efficiency of the plant is lowered.
2. The infiltrated air lowers the partial pressure of steam which means a lower saturation temperature and increased latent heat. Hence, it will require greater amount of cooling water.
3. Because of poor thermal conductivity of air, the rate of heat transfer from the vapour is reduced which requires increased surface area of tubes for a given condenser duty.