induced draft type. Often a bank of such cooling towers are built together to satisfy
the total cooling requirement, as the practical fan size limits the size of each
individual cooling tower. Both counter and cross-flow air paths may be used.
In Figs. 5.11 and 5.13, it is seen that the fan is located behind the packed section
of the tower. From the exit section of the tower, the fan is able to pull the air through
the packing. The designs in Figs. 5.12 and 5.14 place the fan at the entrance to the
tower to push air through the packed section and then out of the tower. The cooling
towers in Figs. 5.11 and 5.13 are called induced draft, and the designs in Figs. 5.12
and 5.14 are called forced draft cooling towers.
The induced draft design normally utilizes larger fans than forced draft. This
allows for higher air exit velocities and lessens problems with recirculation as a
result. Air distribution is often superior using induced draft vs. forced draft design.
As the fan is in the exit in an induced draft cooling tower, this design permits the
warm, moist air to pass through the fan, increasing corrosion problems.
Both induced and forced draft cooling towers can be noisy. Both types will also
obviously consume large amounts of electric power during normal operations and
have more maintenance considerations than natural draft cooling towers. These
designs are practical for rooftops. Also, if sufficient land is available, a bank of
either type of design will not be the dominant feature of the landscape as with large
natural draft hyperbolic cooling towers.
3.8 Cooling Tower Performance Problems
This discussion is intended to be brief, as many good sources of operational advice
are now available particularly on the Internet.
Some of the causes of poor performance in a cooling tower [13–20] and
suggested corrective actions are given below.
Forced Draft Crossflow Tower
Water Outlet
Water Inlet
Air
Outlet
Fill
Fig. 5.14 Forced draft
(mechanical) cross-flow
cooling tower
5 Cooling and Reuse of Thermal Discharges
221
the total cooling requirement, as the practical fan size limits the size of each
individual cooling tower. Both counter and cross-flow air paths may be used.
In Figs. 5.11 and 5.13, it is seen that the fan is located behind the packed section
of the tower. From the exit section of the tower, the fan is able to pull the air through
the packing. The designs in Figs. 5.12 and 5.14 place the fan at the entrance to the
tower to push air through the packed section and then out of the tower. The cooling
towers in Figs. 5.11 and 5.13 are called induced draft, and the designs in Figs. 5.12
and 5.14 are called forced draft cooling towers.
The induced draft design normally utilizes larger fans than forced draft. This
allows for higher air exit velocities and lessens problems with recirculation as a
result. Air distribution is often superior using induced draft vs. forced draft design.
As the fan is in the exit in an induced draft cooling tower, this design permits the
warm, moist air to pass through the fan, increasing corrosion problems.
Both induced and forced draft cooling towers can be noisy. Both types will also
obviously consume large amounts of electric power during normal operations and
have more maintenance considerations than natural draft cooling towers. These
designs are practical for rooftops. Also, if sufficient land is available, a bank of
either type of design will not be the dominant feature of the landscape as with large
natural draft hyperbolic cooling towers.
3.8 Cooling Tower Performance Problems
This discussion is intended to be brief, as many good sources of operational advice
are now available particularly on the Internet.
Some of the causes of poor performance in a cooling tower [13–20] and
suggested corrective actions are given below.
Forced Draft Crossflow Tower
Water Outlet
Water Inlet
Air
Outlet
Fill
Fig. 5.14 Forced draft
(mechanical) cross-flow
cooling tower
5 Cooling and Reuse of Thermal Discharges
221