ID 38

Spray Transfer Efficiency onto a High-Speed Web: Boundary Layer Effects and Manipulation

 

Abstract:

Moving webs are used frequently in the industrial manufacturing world as belts, fabrics, or fiber-based products. In high speed applications, which can be moving upwards of 5000 ft/min, these speeds create a significant boundary layer of moving air. This effect can prevent unwanted buildup on the web surface, but when spraying a liquid solution onto the web surface, such as adding lotion in a tissue making process, this air barrier can present an undesirable challenge. This study characterizes the air barrier, examining: speed, thickness, and shape; and explores techniques to manipulate the boundary for easier application of solution. A test setup with a high-speed belt was constructed, and the boundary later is evaluated using Particle Image Velocimetry (PIV) with and without manipulation. Droplet trajectories and interactions with the belt are investigated. Boundary layer manipulation techniques are applied, and the resulting downstream air barrier is investigated with and without a spray. Physical measurements of the volume of fluid reaching the belt surface are used to quantify the transfer efficiency and the PIV results are used to explain the changes in transfer efficiency across the various air barrier mitigation methods.