Methodology for the assessment of cleanability and geometry optimization using flow simulation on the example of dimple-structured pipe surfaces

Abstract

The hygienic design of machinery, e.g. in the food and pharmaceutical industries, has so far mainly been based on empirical guidelines. Recently developed, efficient models for the numerical simulation of cleaning processes promise a real optimization of the geometry with respect to cleaning. To realize this potential, an approach is provided, which takes into account the variety of cleaning tasks and allows for a generalized evaluation of the cleanability. It is demonstrated on the example of film-like soils in dimple-structured pipes. In this approach, the cleaning behaviour is investigated qualitatively as a function of the relevant cleaning mechanisms and relative to the reference case of a smooth pipe. The overall cleaning performance is calculated from a weighted average of the individual performances. The flow simulations in ANSYS fluent are based on the Reynolds averaged Navier–Stokes equations. The soil behaviour is modelled as a boundary condition to minimize calculation times. Only in the case of viscous shifting, a transient two-phase flow of immiscible fluids is simulated. Three different dimple structures are investigated, where the spherical dimple with sharp edges yields the best results. Through the subsequent optimization of its shape, the cleaning performance even exceeds the value of the smooth pipe.