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ABSTRACT
The cleaning behavior of a soil with physical properties that depend on the wetting time is studied experimentally via the local phosphorescence detection method and simulated numerically in fully developed plane channel flow for Reynolds numbers up to 30,000. A computationally inexpensive general cleaning model is proposed, adopting an existing removal model and coupling it to the turbulent flow field. The influence of the soil on the flow is neglected and the transient behavior of the soil during cleaning is modeled in the form of a transient Dirichlet boundary condition. This approach is innovative for computational fluid dynamics of this phenomenon. The way of determining the model parameters from the experiment is described. The comparison of the simulation results with experimental data reveals very good suitability of the model in the case of a starch soil. A similar good agreement is found for data for a model protein foulant in tube flow from the literature.
Funding
This research project is supported by the Industrievereinigung für Lebensmitteltechnologie und Verpackung e.V. (IVLV), the Arbeitsgemeinschaft industrieller Forschungsvereinigungen “Otto von Guericke” (AiF), and the Federal Ministry of Economic Affairs and Energy (AiF Project IGF 17805 BR).
Nomenclature
| A | = | area, m2 |
| C | = | model parameter, 1/s |
| c | = | concentration, kg/m3 |
| D | = | diffusion coefficient, m2/s |
| Dh | = | hydraulic diameter, Dh = 4A/P, m |
| d | = | diameter, m |
| f | = | stirring frequency, 1/s |
| H | = | channel height or tube diameter, m |
| k | = | mass transfer coefficient, kg/(m2 − s) |
| L | = | length, m |
| m′′s | = | surface soil coverage, kg/m2 |
| = | soil removal rate, kg/(m2 − s) | |
| N | = | number of elements, dimensionless |
| P | = | wetted perimeter, m |
| R | = | removal coefficient, kg/(m − s) |
| R2 | = | coefficient of determination, dimensionless |
| Re | = | Reynolds number, Re = ubDh/ν, dimensionless |
| Rz | = | surface roughness defined by DIN EN ISO 4248, m |
| Sc | = | Schmidt number, Sc = ν/D, dimensionless |
| T | = | time span, s |
| t | = | time, s |
| t90 | = | time with ten percent of the initial soil remaining, s |
| u | = | velocity, m/s |
| x | = | axial coordinate, m |
| y | = | wall normal coordinate, m |
| Greek symbols | ||
| Δ | = | relative deviation, dimensionless |
| ϑ | = | temperature, °C |
| ν | = | kinematic viscosity, m2/s |
| ρ | = | density, kg/m3 |
| ϕ | = | volume fraction of soil, dimensionless |
| φ | = | relative humidity, dimensionless |
| Ψ | = | model parameter, dimensionless |
| Subscripts | ||
| 0 | = | initial |
| b | = | bulk |
| d | = | decay |
| exp | = | experiment |
| max | = | maximum |
| r | = | reptation |
| rms | = | root mean square |
| s | = | soil |
| sim | = | simulation |
| sw | = | swelling |
| t | = | turbulent |
| w | = | wall |
Additional information
Notes on contributors
Matthias Joppa
Matthias Joppa has been a Ph.D. student at the Institute of Fluid Mechanics at Technische Universität Dresden, Germany, since he received his diploma degree in mechanical engineering in 2013. For his diploma thesis, he simulated the flow in a model hydraulic valve by means of large eddy simulation. Currently he is working on the modeling of the impinging jet surface cleaning process for food industry application.
Hannes Köhler
Hannes Köhler has been a Ph.D. student at the Institute of Processing Machines and Mobile Machinery at Technische Universität Dresden, Germany, since 2010. He graduated as an engineer by developing a cleaning monitoring method based on ultraviolet–visible (UV-Vis) spectroscopy. He is part of the working group for Industrial Cleaning Technologies, focusing on impinging jet cleaning. He is in charge of developing and operating test rigs, as well as generating and analyzing experimental data.
Frank Rüdiger
Frank Rüdiger is a research engineer at Technische Universität Dresden (TUD), Chair of Fluid Mechanics. He received his Ph.D. in fluid mechanics and heat transfer in 1994 from TUD, Germany. He was working in several positions in the fields of fluid mechanics and heat and mass transfer. Special fields of interest have been cooling of electrical rotating machines, surface remelting, and cavitation. He is currently head of the research laboratory and projects on heat and mass transfer under numerical and experimental aspects.
Jens-Peter Majschak
Jens-Peter Majschak is a professor of processing machines and processing technology at Technische Universität Dresden and Head of Branch Lab for Processing Machinery and Packaging Technology of Fraunhofer IVV, since 2004. He received his Dr.-Ing. in processing machinery design in 1997 from the Technische Universität Dresden. From 1995 to 2000, he worked as a research engineer at Fraunhofer Application Center for Processing Machinery and Packaging Technology. From 2000 to 2001, he was a project engineer at IZK GmbH and became the Head of Department for Technological Information Systems at Fraunhofer Institute for Processing Technology and Packaging Technology in Freising in 2002. His main working field is hygienic design and cleaning technologies for processing machines. Since 2013, he has been a regular member of the Sächsische Akademie der Wissenschaften zu Leipzig.
Jochen Fröhlich
Jochen Fröhlich is a professor of fluid mechanics at Technische Universität Dresden (TUD), Germany. He received his diploma degree in mechanical engineering from RWTH Aachen and his Ph.D. from Université de Nice–Sophia-Antipolis, France. Since 2007, he has held the Chair of Fluid Mechanics at TUD, and since 2010, he has been managing director of the Institute of Fluid Mechanics. His main research contributions cover numerical methods for fluid problems and their implementation on high-performance computers, as well as the simulation of turbulent flows and multiphase flows.