Turbulator - in Rotating Drums

In Rotating Drums

Axial bars are placed on the inside surface of rotating steam-heated drums to create turbulence in the rimming condensate layer. If the spacing of the bars is chosen correctly, resonant waves are created in the condensate film, between each pair of bars. This significantly increases the level of turbulence, even at high drum speeds. This increase in turbulence reduces the resistance to heat transfer from the steam, through the condensate film, to the drum shell. The increase in heat transfer can be as large as 50%, even when compared to the performance of drums with modern, close clearance rotating syphons. The maximum increase, however, requires the bars to operate with the optimum condensate layer thickness.

In addition, these axial bars can reduce the speed at which the condensate layer will move from the cascading stage to the rimming stage. This can provide a significant reduction in the power and torque required to drive the rotating cylinder. When operating with the right configuration of bars and the corresponding optimum condensate depth, these axial bars achieve a high rate of heat transfer and a high degree of heat transfer uniformity.

Axial bars are commonly used inside rotating drums in the paper and fabric manufacturing industries, for example, in paper machine drying cylinders and similar steam-heated cylinders that are rotating at high speeds where the condensate would normally be in a rimming condition. These bars increase the drying rate and uniformity of the cross-machine moisture profile of the paper. A number of different configurations of axial bars have been used in these applications, with differing mechanical constructions. The term “Turbulator” is a registered trademark of Kadant Johnson and defines a specific configuration of axial bars used in these rotating drum applications.