The water injection before the axial compressor aims at decreasing both the temperature of the working
fluid and the polytropic exponent in the compression process. Thus, we can save some compression work.
This method has been used in a jet engine when a fighter plane speeds up. However, the difference is that
what is injected in a jet engine is water, alcohol, etc.
The water vapor in the compressed air can easily be extracted by a surface heat exchanger. With the
same temperature, the humidity ratio of the saturated wet air at high pressure P4 is only about P3/ P4 of
that at the pressure P3. The method of using compressed air to acquire dry air has been used in some
workshop in southern China.
The mount of the water extracted from high pressure wet air (4 to7)can reach 18-30 g/kg(da). And
the mount of the latent heat discharged from vapor condensed, about 45-75kJ/kg(da), exceeds the sensible
heat from air, 30-50 kJ/kg(da). For this reason, refrigeration load in this air-vapor regenerated refrigeration
cycle depends on a combination of the sensible heat of air and the latent heat of vapor. The regenerated
cold comes from the rejected air to outdoor. Usually, the cold cannot be used at other system. Use of it
could increase the equivalent COPE of this cycle.