Flow patterns and cleaning behaviour of horizontal liquid jets impinging on angled walls

Liquid jets are widely used in cleaning operations in the food sector. Morison and Thorpe (2002) reported an experimental investigation of the flow patterns and cleaning behaviour of horizontal jets impinging on vertical walls. The Wilson et al. (2012) model, which described Morison and Thorpe's flow pattern data well, is extended to describe the flow pattern generated by a liquid jet, approaching a surface at a given angle to the horizontal, impinging on a plate inclined at a known angle to the vertical. The results are compared with experimental data collected for horizontal water jets impinging on inclined Perspex and glass plates. Tests employed nozzle diameters of 1, 2 and 3 mm at room temperature, using flow rates of 0.78-2.23 g s(-1), 3.7-9.9 gs(-1) and 7.1-17.3 gs(-1) (0.025-0.062 m(3) h(-1)) respectively. These are lower than industrial cleaning flow rates. The angle at which the horizontal jet impinged on the plate was varied from 30 degrees to 120 degrees. Two important dimensions are evaluated: (i) the width of the fast moving radial flow zone on the plate (the region bounded by the film jump, the feature similar to a hydraulic jump) at the plane of impingement; (ii) the distance on the plate to which the radial flow zone extends above the point of impingement. Both are described reasonably well by the model. Empirical relationships are reported for the width of the wetted region at the level of impingement, and the maximum width of the draining film. A short study of cleaning of layers of washable paint on glass, similar to the tests reported by Morison and Thorpe, show that the cleaning model recently developed by Wilson et al. (2014) gives a good description of the initial cleaning of such layers using an impinging stationary coherent water jet. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.