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Article

High Schmidt number “Washout” of a soluble contaminant downstream of a backward-facing step

Min, D., Fischer, P.F., Pearlstein, A.J.

2020Intl. J. Heat Mass Transfer159119740

Keywordscavity flow, cleaning, mass transfer

DisciplinesChemical Engineering, Fluid Mechanics, Mechanical Engineering

CategoryNumerical simulations

Non-expert summaryThis is a dynamic simulation of removal of a soluble component by diffusive mass transfer from the shadow region of a 2-D backward facing step. The scenario is this: a fully developed laminar flow (Reynolds number of 10 and 100) between two parallel plates encounters a shallow 90 degree step in the lower plate (the step height is 0.02 x the initial duct height). A nonreactive soluble component is present in the region next to the step, essentially a square of contaminated fluid. The washout of this packet of fluid, by flow over the step and diffusion, is modelled for Schmidt numbers between 7 and 2650. Streamlines and contentration contours over time are mapped and characteristic timescales are computed. The results will be of interest to those interested in the washout of contaminated liquids in shallow recesses.

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Article

2. Non-chlorine detergent formulations as an alternative for unpasteurised milk removal from stainless steel surfaces

1. Joels Wilson-Nieuwenhuis, Jim Taylour, Luciana C. Gomes, Stephen Lynch, David Whitehead, Kathryn A. Whitehead

20243. Journal of Food Engineering374112031

DisciplineSurface Chemistry

CategoryLaboratory experiments

Non-expert summaryHygiene is a major concern in the dairy industry, and detergents based on hypochlorite have commonly been utilised for cleaning-in-place (CIP) regimes. However, due to concerns about chlorate residues entering the milk processing chain, new detergent alternatives that are free of chlorate sources are required. This work looked at the cleaning efficacy of two new formulations were developed based on ethylenediaminetetraacetic acid (EDTA) and wetting agents. Stainless steel surfaces were fouled with milk and cleaned once or 10 times using water, a caustic-EDTA product, a sodium hypochlorite product, an acid, or new cleaning formulations (Product A and Product B). The results demonstrated that the use of acid did not result in successful cleaning. The two new products performed well, with Product B performing equivalently during cleaning compared with the established hypochlorite or caustic-EDTA products. Product A exhibited better cleanliness than the other detergents tested. When allergen removal was considered, residual material was found to be retained on the surfaces, regardless of the cleaning type used. This study suggests that the new product formulations may be used to replace hypochlorite-based detergents to increase the hygienic status of a surface.

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Review article

Degradation of anthraquinone dyes from effluents: a review focusing on enzymatic dye degradation with industrial potential

E. Routoula; S. V. Patwardhan

2020Environmental Science and Technology54(2)647-664

Keywordsdye degradation, enzymatic processes, water pollution

DisciplinesChemical Engineering, Chemistry

CategoryReview

Non-expert summaryVery little attention has been given to anthraquinone dyes, which pose a serious environmental problem as their reinforced structure makes them difficult to degrade naturally. Existing methods of decolorization might be effective but are neither efficient nor practical due to extended time, space, and cost requirements. Attention should be given to the emerging routes for dye decolorization via the enzymatic action of oxidoreductases, which have already a strong presence in various other bioremediation applications.

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Article

Visual inspection of surface sanitation: defining the conditions that enhance the human threshold for detection of food residues

Daeschel, D., Singh Rana, Y., Chen, L., Cai, S., Dando, R. and Snyder, A.B.

2023Food Control149109691

Keywordscleaning, decontamination

DisciplinesSocial sciences

CategoriesField work, Statistical analysis

Scale1e-6 m, 1e-6 to 1e-3 m / 1 to 60 s

Non-expert summaryVisual inspection is widely used in assessing and monitoring cleaning, sanitation and decontamination. This experimental study explored the degree of residual soiling on equipment surfaces that lies below the limit of visual detection. The goal of this study was to evaluate the limit of detection of visual inspections and establish evidence-based strategies to improve the implementation of this activity. 101 respondents completed a visual sensory test where each one looked at viewed 15 stainless steel and 15 white high density polyethylene sheets, clean or soiled with dry wheat flour, in a randomly generated order. They were asked if they could visually detect food residue on each surface and, if so, if the surface should be re-cleaned. They were also asked to answer this when they could touch the surfaces with a gloved hand. The impact of training, use of illumination, viewing angle and colour-contrast are quantified. The results provide a quantitative measure of the effectiveness of visual inspection, and factors than can influence this.

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Article

Experimental investigation of laminar and turbulent displacement of residual oil film

Zhang, Y., Barrouillet, B. and Skadsem, H.J.

2023Scientific Reports1321120

Keywordscleaning, flow displacement, shear flow, thin film

DisciplinesChemical Engineering, Fluid Mechanics, Mechanical Engineering

CategoryLaboratory experiments

Scale1e-6 to 1e-3 m / 1 to 60 s

Non-expert summaryThis paper reports an experimental study of the removal of thin oil films from the wall of a cylindrical tube by a flow of water. The removal of the oil film is measured by monitoring dye concentration in the flushing liquid leaving the system: local extents of removal were not measured. The authors investigated the effect of the flow regime of the displacing fluid (water Reynolds numbers ranged from 1480 to 12690), the duration of the displacing fluid flow, and the estimated wall shear stress imposed on the film. When the volume of fluid is limited, the largest displacement efficiency was observed at Re = 7000-8000 (named the intermediate turbulent regime). The largest Reynolds number flows were most effective for achieving complete cleaning over a long time period.

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Article

Numerical investigation of ice pigging isothermal flow in water-supply pipelines cleaning

Hu, J. and Tao, T.

2022Chemical Engineering Research & Design182428-437

Keywordscleaning, detachment, flow displacement, heat transfer, hydrodynamics, multiphase flow

DisciplinesChemical Engineering, Fluid Mechanics

CategoryNumerical simulations

Scale1e-3 to 1 m / 1e-3 to 1 s, 1 to 60 s

Non-expert summaryIce-pigging is a cleaning method in which a dense slurry (to be removed) is pushed along a channel (often a pipe, but more complex geometries can also be cleaned by this method) by an upstream solid-liquid thick ice slurry. The authors use the commercial CFD code FLUENT to evaluate a numerical model of this multiphase (solid-liquid) material undergoing pipe flow. In this coupled Eulerian-Eulerian description the two phases are treated separately as continuous phases coupled by pressure and interphase forces. They validate their model against experimental data from literature and report the predicted ice volume fraction, wall shear stress and melting rate. The results show strong inhomogeneity in the solid content (ice volume fraction).

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Article

Lessons to learn from roadmapping in cleaning and decontamination

Wilson D. I., Christie G., Fryer P. J., Hall I. M., Landel J. R., Whitehead K. A.

2022Food and Bioproducts Processing135156-164

Keywordscleaning, decontamination

CategoryReview

Scaleless than 1e-9 m, 1e-9 to 1e-6 m, 1e-6 m, 1e-6 to 1e-3 m, 1e-3 m, 1e-3 to 1 m, 1 to 10 m, 10 to 1000 m, greater than 1 km / less than 1e-3 s, 1e-3 to 1 s, 1 to 60 s, 1 to 60 min, 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThis article presents an interdisciplinary roadmap showing the importance of cleaning and decontamination activities across a range of socio-economic sectors and in daily life. It captures the expertise and state-of-the art in terms of the fundamental understanding of the underpinning science behind cleaning and decontamination activities, as well as its practical implementation. The roadmap also highlights shortcomings and critical needs in the field at the scientific and practical levels, with some strategies to address them.

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Article

Shear flow over a protuberance on a plane wall

Pozrikidis, C.

1997Journal of Engineering Mathematics3129-42

Keywordsdecontamination, flow displacement, shear flow

DisciplinesApplied Mathematics, Fluid Mechanics

CategoryNumerical simulations

Non-expert summaryMany cleaning and decontamination operations employ a flow to detach or move a particle or foreign element (e.g. a piece of dust, baterium or a spore) from a surface. The presence of the element disturbs the flow near the wall. Knowledge of the flow field and the forces imposed on the element is useful for predicting or quantifying removal. This paper considers a simple shear flow of a Newtonian fluid over an axisymmetric protuberance (with uniform shape) on a plane wall. The full 3-D problem is formulated in terms of three scalar Fredholm integral equations of the first kind and is solved using a boundary-element method. The hydrodynamic force and torque exerted on the protuberance, and distribution of shear stresses, are calculated. There is good agreement with previous analytical computations for hemi-spherical and spherical shapes.

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Article

Lift, drag and added mass of a hemispherical bubble sliding and growing on a wall in a viscous linear shear flow

Legendre, D., Colin, C., Coquard, T.

2008Phil. Trans. R. Soc. A3662233-2248

Keywordsflow displacement, shear flow

DisciplinesFluid Mechanics

CategoryNumerical simulations

Non-expert summaryThe Navier-Stokes equations for the three-dimensional flow of a Newtonian fluid around a hemispherical bubble simultaneously sliding along a flat wall and growing are solved. The forces experienced by the bubble (lift, drag and added mass) are calculated for bubble Reynolds numbers greater than or equal to 0.01 and flow Reynolds numbers < 2000. The bubble does not change shape. The scenarios studied are (i) an immobile bubble in a linear shear flow; (ii) a bubble sliding along the wall in an otherwise stagnant fluid; and (iii) a bubble sliding in a linear shear flow. The results are presented in the form of dimensionless coefficients.

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Article

Aging is important: Closing the fouling–cleaning loop

Ishiyama, E.M., Paterson, W.R., Wilson, D.I.

2014Heat Transfer Engineering35(3)311-326

Keywordscleaning, heat transfer

DisciplinesChemical Engineering

CategoryTheoretical modelling

Scale1e-3 m, 1e-3 to 1 m / 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThis paper considers the management of heat exchanger units subject to regular cleaning and thus regular cleaning. A quantitative model is needed to support the decision of when to clean an exchanger, giving rise to repeated cycles of fouling and cleaning. The initial stages of fouling are strongly influenced by the effectiveness of the most recent cleaning step and, similarly, the effectiveness and rate of cleaning are determined by the extent and nature of the deposit layer present on the surface. Deposit aging is an important factor in this, as an aged deposit is usually more difficult to clean. Ageing therefore introduces an element of choice into fouling–cleaning operating cycles, between in situ “chemical” methods and ex situ “mechanical” methods, with associated differences in effectiveness, time, and cost. The cleaning scheduling problem is presented in terms of the choice of cleaning method, as well as the timing of cleaning. A process scale model is used, with the performance of units described by lumped parameter (i.e. not detailed) models. Dimensionless groups are obtained which capture the scaling involved. Case studies are used to illustrate the concepts.

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Article

Mechanisms of photoresist dissolution

Hunek, B., Cussler, E.L.

2002AIChEJ48(4)661-672

Keywordscleaning, decontamination, mass transfer

DisciplinesChemical Engineering, Chemistry

CategoryLaboratory experiments

Scale1e-6 to 1e-3 m / 1e-3 to 1 s, 1 to 60 s, 1 to 60 min

Non-expert summaryPhotoresists are an example of long chain molecules which dissolve in the presence of alkali. Dissolution involves the transport of hydoxyl ions (OH-) into the layer: they react with the photoresist and, depending on the temperature (above or below the upper critical solution temperature, UCST), it will either be transported by diffusion through the fluid boundary layer (above UCST) or form a gel phase (below the UCST), introducing an additional diffusion step in the reaction and mass transfer processes. A physico-chemical model of the process is presented here, applied to novolak resins, which can be applied to other polymeric systems including printing inks and dairy protein foulants. Experiments are performed with a spinning disk apparatus, which gives well defined mass transfer conditions.

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Miscellaneous

Waste Estimation Support Tool (WEST)

US Environment Protection Agency

2021

Keywordscleaning, decontamination

DisciplinesMicrobiology, Statistics & Probabilities

Scale1 to 10 m, 10 to 1000 m, greater than 1 km / 1 to 60 min, 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThe US Environment Protection Agency (EPA) has generated a number of management tools related to cleaning and decontamination. The EPA website states that "Management of waste from a radiological dispersal device (RDD) incident would likely constitute a large part of the remediation cost and effort. The U.S. EPA’s RDD Waste Estimation Support Tool (WEST) is a planning tool for estimating the potential volume and radioactivity levels of waste generated by a radiological incident and subsequent decontamination efforts. WEST supports decision makers by generating a first-order estimate of the quantity and characteristics of waste resulting from a radiological incident, and allows the user to evaluate various decontamination/demolition strategies to examine the impact of those strategies on waste generation. "

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