Prediction of hygiene in food processing equipment using flow modelling

Computational fluid dynamics (CFD) has been applied to investigate the design of closed process equipment with respect to cleanability. The CFD simulations were validated using the standardized cleaning test proposed by the European Hygienic Engineering and Design Group. CFD has been proven as a tool which can be used by manufacturers to facilitate their equipment design for high hygienic standards before constructing any prototypes. The study of hydrodynamic cleanability of closed processing equipment was discussed based on modelling the flow in a valve house, an up-stand and various expansions in tubes. Results show that cleaning can be efficient in complex geometries even when the critical wall shear stress (determined in uni-axial flow) is not exceeded. This renders the need for considerations concerning three-dimensional flow, the degree of turbulence and the type of flow pattern. The controlling factors for cleaning identified were the wall shear stress and the nature and magnitude of recirculation zones present.