Jens-Peter Majschak

Modeling and Validation of the Mechanism of Pulsed Flow Cleaning

The enhancement of the cleaning efficiency of cleaning-in-place (CIP) systems is playing a key role in improving food production. Cleaning models based on computational fluid dynamics (CFD) can be a tool that enables identifying locations in a plant that are difficult to clean and enhances the cleaning efficiency by appropriate fluid dynamics, that is, the application of transient flow. A CFD cleaning model was developed that is based on the assumption of a mass transfer controlled cleaning process. The physical basis of the model is the analogy between heat and mass transfer. A validation of the cleaning mechanism, using experimental data of local cleaning times in several complex geometries with varied static and transient flow velocities, was carried out. A modified waxy maize starch with phosphorescent tracers was used as model food soil. The received results show a good agreement between the measured and simulated cleaning times. The cleaning model is suitable for the calculation of the cleaning progress for all fouling systems, where the cleaning mechanism is mass transfer controlled. It is now possible to visualize the effect of complex pipe geometries or inappropriate hygienic design on the overall cleaning time. Especially in locations difficult to reach with steady flow, the application of pulsed flow shows a shorter cleaning time. Based on the presented new CFD model the local cleaning efficiency can be predicted.

Experiments and Simulations on the Cleaning of a Swellable Soil in Plane Channel Flow

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.

Investigations on the heating effect of PE-LD induced by high-intensity focused ultrasound.

High-intensity focused ultrasound is widely applied in tissue treatment as well as for heating of solid polymer materials. Previous studies investigating the heating effect in polymer materials utilized sound transmission through water or other fluids at low HIFU power. In this study, the ultrasonic transducer possesses a solid sound conductor made of aluminum and a high HIFU power of above 100W was applied to heat solid PE-LD samples. Temperature measurements were performed by calibrated non-invasive infrared thermal imaging. A strong heating effect with heating above melting temperature and evaporation temperature within less than 1s of irradiation was observed. Furthermore, the acoustic coupling defined by the force applied by the ultrasonic applicator to the polymer material was found to be fundamental to induce the heating effect. This investigation reveals HIFU for new applications in the field of polymer processing.

Commissioning new applications on processing machines: Part I - process modelling:

The subject of this splitted article is the commissioning of a new application that may be part of a processing machine. Considering the example of the intermittent transport of small-sized goods, for example, chocolate bars, ideas for increasing the maximum performance are discussed. Starting from an analysis, disadvantages of a conventional motion approach are discussed, and thus, a new motion approach is presented. For realising this new motion approach, a virtual process model has to be built, which is the subject of this article. Therefore, the real process has to be abstracted, so only the main elements take attention in the modelling process. Following, important model parameters are determined and verified using virtual experiments. This finally leads to the possibility to calculate useful operating speed–dependent trajectories using the process model.

Study on the application of cleaning models with high speed water jets to CIP-processes

Original scientific paper To meet consumer safety and high product quality there is a need of reliable cleaning processes in the food industry. To keep competitive position it is necessary to control costs of those cleaning in place (CIP) processes e.g. expenses for fresh and waste water, detergents and to minimize downtime of the production facilities. The removal of food soils with water droplet sprays are very little researched, especially the mathematical modelling. In this paper we show that the high pressure model of Leu et al. can be applied to low pressure spray cleaning of a food soil with marginal adaptations. We used an existing analytical model for the relation of cleaned width as a function of the standoff distance and considered the different structure of the water spray as well as a food specific cleaning behaviour. We validated the analytical model with experimental results by varying the equivalent nozzle diameter.

Prediction of Cleaning by Means of Computational Fluid Dynamics: Implication of the Pre-Wetting of a Swellable Soil

Abstract The cleaning behavior of a pre-wetted soil is studied experimentally and modeled numerically for the prototypical case of plane channel flow. One of the channel walls is soiled with a food-based model soil containing luminescent tracer particles to perform space- and time-resolved investigations of the cleaning process. Pre-wetting is applied for a few minutes before the soil removal is started with flow of Reynolds number up to 20,000. Physical model and simulation are based on a transient boundary condition to represent the behavior of the soil. Pre-wetting is taken into account by an initial removal of a certain amount of soil due to cohesive separation and the subsequent cleaning modeled as being limited by a diffusive process. Compared to a conventional multiphase simulation, the computation time is lowered by about three orders of magnitude. The results obtained with this elementary approach match the experiments astonishingly well.

Commissioning new applications on processing machines: Part II – implementation

The subject of this splitted article is the commissioning of a new application that may be part of a processing machine. At the example of the intermittent transport of small sized goods, for example, chocolate bars, ideas for increasing the maximum machine performance are discussed. Therefore, optimal process motion profiles are synthesised with the help of a computer simulation. In the first part of the paper, the modelling of the process was shown. This second part focusses on implementing the simulated motion approaches on an experimental test rig, whereby the new motion approach is compared to the conventional approach. Hence, the increasing of the performance can be proven. Eventually, possibilities for an online process control are observed which are necessary to prevent unstable process conditions.

Application of Hollow Sphere Structures and Composites in Processing Machines

The term processing machines refers to a large variety of machines and equipment for the mass production of consumer goods. Processing machines are often specially tailored according to the particular processing task they have to fulfill, such as pasteurising milk or packing goods. Furthermore the vast majority is characterised by large production outputs, demanding high processing velocities and fast moving parts. A special application is that of the food and drug processing area. Due to high quality standards there are special requirements for material surfaces to be considered if surfaces are in contact with the manufactured product. This chapter deals with the special demands concerning dedicated engineering materials that occur from state of the art processing machines. Specific requirements ranging from high damping abilities for support components to high stiffness and low weight for fast moving tools are presented by means of a general classification of processing machines into four functional areas. Accordingly, the proposed hollow sphere structures and similar material classes are presented and applied on each of these four areas.

Modifizierte Oberflächen verringern Verschmutzungen

Eine aktuelle Untersuchung gibt Aufschluss uber den Einfluss der energetischen und topographischen Oberflacheneigenschaften auf die Verschmutzungsneigung und Reinigbarkeit verschiedener modifizierter Oberflachen bei Lebensmittelverschmutzungen.