Page 313 - Applied Process Design For Chemical And Petrochemical Plants Volume III

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272 Applied Process Design for Chemical and Petrochemical Plants

Adjustable Shutters
Shutters mounted above the cooling sections serve to protect them
from overhead wind, snow, ice, and hail. In addition, they are also
used to regulate, either manually or automatically, the flow of air
across the finned tubes; thus, they control the process fluid outlet
temperature.

Controllable Pitch Fan
The controllable pitch fan provides an infinitely variable air delivery
across the K-fin sections through automatic changes in the fan blade
angle. The temperature can be closely controlled to meet the varying
demands of operating conditions and fluctuating atmospheric tem-
peratures with appreciable power savings under low load conditions.
For certain control applications, the ability of this fan to pump air
backwards with negative blade angles is used.

Combination Controls
The combination of adjustable shutters with variable speed drive or
with controllable pitch fan is frequently used for close fluid tempera-
ture control. This system is particularly useful during start-up and
shut-down procedures in which fluids are subject to freezing in cold
ambient temperatures. It is also well-adapted to fluid temperature
control while operating under high wind and freezing conditions. This
diagram shows a two-speed electric motor with automatically
adjustable shutters. The arrangement lends itself to many cooling
services while effecting a horsepower savings through the use of the
two-speed motor.

Figure 10-192. Schemes for temperature control of air-coolers. (Used by permission: Griscom-Russell/Ecolaire Corporation.)

Figure 10-193. Typical dimensions for air-coolers with two fans. (Used Figure 10-194. Typical dimensions for air-coolers with one fan. (Used
by permission: Griscom-Russell/Ecolaire Corporation.) by permission: Griscom-Russell/Ecolaire Corporation.)