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Turbulator Bars

Kadant Johnson Turbulator bars are a series of axial bars which rim the inner circumference of a dryer shell. Under the right conditions, these bars will create greater turbulence within spinning condensate, reducing resistance to heat transfer and improving dryer efficiency.

Turnbuckle Assembly
Compression Bolt Type

Turnbuckle Assembly
Disc Spring Type

1.When condensate first reaches the rimming stage, large amplitude oscillations produce turbulence.

2.As speeds increase, condensate rimming becomes more laminar, oscillation reduces, and turbulence decreases.

3.Turbulator bars restore turbulence within the condensate, and improve heat transfer rates.

How Turbulator bars work

To understand how Turbulator Bars work, it is necessary to first understand how condensate inside a dryer shell behaves at various speeds.
When rotational speed increases, so do friction and centrifugal force, which carry condensate upward and downward in the direction of dryer rotation, eventually condensate rim becomes more firmly pressed onto the dryer shell.

  1. In this rimming stage, gravity causes deceleration of condensate traveling upward and acceleration of condensate traveling downward. This variation in speed causes oscillation and produces turbulence in the condensate that improves heat transfer rates.
  2. If rotational speed continues to increase, oscillation decreases, the condensate film becomes more laminar, and therefore is more resistant to heat transfer.
  3. When this laminar rimming occurs, Turbulator bars can be placed inside the dryer to break up the rimming condensate film. Turbulence is reintroduced into the condensate layer, heat transfer rates increase - and dryer efficiency could be improved.

When to use Turbulator bars

Turbulator bars can make a great contribution to improved drying capacity and paper quality - but only if they are used under the proper conditions.
For instance, Turbulator bars are usually not effective at speeds below the laminar rimming stage, where sufficient turbulence is already present in the condensate. In these conditions, the close clearance syphon system will hold condensate levels to a minimum, allowing maximum heat transfer rates without the expense of additional equipment.
In addition, speed alone is not the sole criterion for adding Turbulator bars. The effectiveness of Turbulators is determined by an interrelationship between dryer speed and condensing load.
Kadant Johonson Research Center created the statistical model data to make clear the interrelationship among dryer speed, condensing rate and average dryer shell temperature through the intensive tests using Kadant Johnson Rotary Syphon, Stationary Syphon and Turbulator bars.
The certain interrelationship between dryer speed and condensing rate could improve the uniform profile with the increased heat transfer from steam to dryer shell, when installing Turbulator bars.
This model data is very important to evaluate the selection for the improvement of dryer shell temperature profile, heat transfer and productivity.
According to the analysis of driving conditions based on dryer speed, calculated condensing rate and the statistical model data, cost-effective hardware could be selected. The driving conditions should be evaluated individually per each dryer because of the interrelationship among dryer speed, condensing rate and heat efficiency.

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