9 models from 100 to 1000 kW
Principle of operation - operation modes
Combined dry/wet operation mode
In this mode the fluid to be cooled is fed first to the finned
coil and then to the prime surface coil from where the cooled fluid
exits. Spray water is drawn from the cold water sump and pumped to the
water distribution system above the prime surface coil.
By wetting the prime surface coil, evaporative cooling occurs. The spray
water falls from the prime surface coil over a wet deck surface, which
enhances the evaporative heat transfer. Air is drawn through both the
prime surface coil and wet deck sections where it is saturated and picks
The air is, however, still cold enough to achieve significant cooling
within the finned coil which is installed at the discharge above the
fan(s). In the dry/wet mode therefore both sensible and evaporative
heat transfer are used.
Compared to a conventional evaporative cooler significant water savings
can be obtained at peak conditions. At reduced heat load and/or ambient
temperatures the evaporative cooling portion, and hence water usage,
are further reduced when the flow fed to the wet prime surface coil
is gradually reduced. This is accomplished by a modulating flow control
valve, which controls the design outlet fluid temperature.
This control arrangement automatically assures maximum use of sensible
cooling in the finned coil and minimum use of evaporative cooling in
the wet prime surface coil. Heat transfer method and flow control are
arranged to achieve maximum water saving in the dry/ wet mode.
The adiabatic mode occurs when the fluid to be cooled completely
bypasses the wet prime surface coil. No heat is rejected from this coil
and the recirculating spray water merely serves to saturate and adiabatically
pre-cool the incoming outside air. In most climates the ambient air
still has considerable potential for gaining moisture.
Thus adiabatic cooling of the air results in significantly lower air
temperatures which greatly increase the heat transfer efficiency. Compared
to conventional evaporative cooling equipment the water consumption
is much reduced.
During the dry operation mode the spray water loop is turned
off. The fluid to be cooled is fed from the finned coil to the prime
surface coil. The modulating flow control valve remains fully open to
ensure both coils receive the full fluid flow, hence the maximum heat
transfer surface is available.
It is obvious that in this mode no water consumption occurs.