Managing airflow
The control of airflows is critical to the operational success of a dryer. Proper dryer design and the implementation/control of specific dryer components is the foundation of proper airflow management. And it
should be noted that controlling velocity alone, though important, will not
suffice. Airflow direction and volume play key roles in the proper tuning of a
dryer system.
The legacy design of most horizontal dryers provided a circular airflow,
as depicted in Figure 4. The deficiencies of this design are with differential
pressures and variances in cross-bed moistures. This can be mitigated by
alternating the circular direction of

the airflow as the product travels from
section to section.
An improved and more efficient
airflow design, as depicted in Figure
5 and with the Extru-Tech AirFlow II
dryer, is commonly referred to as a
center-airflow design. The symmetrical
layout of the dryer components
delivers benefits in the following
areas:
Airflow balance; ■
Airflow volume; ■
Airflow segregation ■
(via sub-floor);
Temperature profiling. ■
Figure 4. Legacy airflow:
horizontal dryers

Cold Air Intake

Re-Circulated
Air

Most horizontal dryers had a legacy design
that provided a circular airflow, which

could lead to differential pressures and
variances in cross-bed moistures.
Figure 5. Center-airflow design

Fresh Make-Up Air

Exhaust Air

Heated Air

The symmetrical layout of these dryer components delivers an improved and more efficient
airflow design than in traditional ones.