PREDICTING THE CLEANABILITY OF MIX-PROOF VALVES BY USE OF WALL SHEAR STRESS

The purpose of this work was to predict the outcome of a practical cleaning test for closed food-process equipment by examining wall shear stress distributions in the equipment estimated from Computational Fluid Dynamics (CFD) simulations. Such predictions make evaluation and improvement of hygienic design of equipment prior to prototype production possible. To do this, knowledge of hydrodynamic cleaning effects is required. The importance of hydrodynamics was shown by cleaning tests on a mix-proof valve (MPV) and a straight pipe. The MPV was easier to clean than a straight pipe. An explanation to this was sought in this work by the idea of a critical wall shear stress. A radial flowcell (RFC) was used for prediction of the critical wall shear stress. Prediction of cleanability in the MPV was performed by comparison of wall shear stress estimated in the MPV by CFD to the critical wall shear stress found in the RFC. Cleanability was under-predicted by the use of simulated wall shear stress compared with cleanability estimated from actual cleaning trials.

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