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P Legentilhomme - One of the best experts on this subject based on the ideXlab platform.
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application of turbulent pulsating flows to the bacterial removal during a Cleaning in Place procedure part 2 effects on Cleaning efficiency
Journal of Food Engineering, 2009Co-Authors: Walid Lel, P Legentilhomme, Thierry Enezech, Jack Legrand, Le C GentillelievreAbstract:Pulsating turbulent flows effects on Cleaning in Place procedure of straight pipes were investigated for various pulsations parameters (frequency and amplitude) and mean velocities of the flow. Pulsations generation was made with a new system which allows high amplitude of pulsations. Experiments showed the contribution of the different pulsation parameters, in the removal of adhered bacterial spores, in addition to the effect of the mean velocity of the flow. A high level of the Cleaning rate is observed despite the reduction of the magnitude of the mean velocity. This result can be explained by the effect of the two pulsations parameters (amplitude and frequency) which ensure a high wall shear rate. The study of the Cleaning kinetics has shown the increase of the removal constant rate of spores using pulsed flow in comparison with the use of a steady turbulent flow.
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application of turbulent pulsating flows to the bacterial removal during a Cleaning in Place procedure part 1 experimental analysis of wall shear stress in a cylindrical pipe
Journal of Food Engineering, 2009Co-Authors: Walid Lel, Thierry Enezech, Le C Gentillelievre, Jack Legrand, P LegentilhommeAbstract:Abstract The effects of pulsating turbulent flows on wall shear stress components were investigated in a straight pipe using the non-intrusive electrochemical method. Experiments were made using a new pulsation generator system which allows high amplitude pulsations in addition to a perfect stability of the installation. Maximum pulsation frequency equal to 2.86 Hz is used, above which fluid inertia dominates over most part of the flow field. Analysis showed that pulsating flows induce an increase of local velocity gradient at the wall pipe. This result is explained by the periodic renewal of the boundary layers. Spectral analysis showed high increasing rates of the fluctuation energy for the different pulsating conditions in comparison with a steady flow. The tested condition involving a recirculation flow induced a modification in the energy dissipation cascade, which can be explained by the redistribution of eddies size near the wall.
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Hygienic Design: Effect of Hydrodynamics on the Cleanability of a Food Processing Line
AIChE Journal, 2008Co-Authors: W. Blel, P Legentilhomme, Thierry Benezech, J. Legrand, Caroline Le Gentil-lelièvreAbstract:in Wiley interScience (www.interscience.wiley.com). Hydrodynamic effect on the numbers of adhering Bacillus cereus spores before and after Cleaning in Place of part of a dairy processing line was investigated using nonin-trusive flow characterization (local wall shear stresses and velocity profiles measurements). Geometrical changes, like gradual asymmetric pipe contractions and pipe expansions and bends, induce nonhomogeneous distribution of the initial and the residual soiling levels. Moreover, the recirculation zone resulting from the flow detachment after the expansion, allowed to explain the high level of adhered spores downstream of this geometrical change due to the generated shear stresses. The resistance to Cleaning processes in the same zones is mainly governed by the adhesion strength of spores induced by the applied flow rate in the contamination step. Welding and gasket areas, located at different positions in the loop, constituted deposit spots for spores and remained difficult to clean despite high-shear stress forces involved.
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Hygienic design : effect of hydrodynamic on the cleanability of a food processing line
AIChE Journal, 2008Co-Authors: W. Blel, P Legentilhomme, Thierry Benezech, J. Legrand, - Legrand, J., Caroline Le Gentil-lelièvreAbstract:Hydrodynamic effect on the numbers of adhering Bacillus cereus spores before and after Cleaning in Place of part of a dairy processing line was investigated using nonintrusive flow characterization (local wall shear stresses and velocity profiles measurements). Geometrical changes, like gradual asymmetric pipe contractions and pipe expansions and bends, induce nonhomogeneous distribution of the initial and the residual soiling levels. Moreover, the recirculation zone resulting from the flow detachment after the expansion, allowed to explain the high level of adhered spores downstream of this geometrical change due to the generated shear stresses. The resistance to Cleaning processes in the same zones is mainly governed by the adhesion strength of spores induced by the applied flow rate it? the contamination step. Welding and gasket areas, located at different positions in the loop, constituted deposit spots for spores and remained difficult to clean despite high-shear stress forces involved. (C) 2008 American institute of Chemical Engineers.
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effect of flow arrangement on the removal of bacillus spores from stainless steel equipment surfaces during a Cleaning in Place procedure
Chemical Engineering Science, 2007Co-Authors: Walid Lel, P Legentilhomme, Thierry Enezech, Jack Legrand, Caroline Le GentillelievreAbstract:influence of local wall shear stresses measured at different circumferential positions of a series of various piping elements (such as gradual or sudden contractions or expansions) on the removal of Bacillus spores during a Cleaning in Place (CIP) procedure was studied. The variation in residual contamination levels observed for the three tangential positions analysed was induced by the flow disturbance caused by various interacting geometric elements, essentially the bend localised upstream of the tested pipes. The recirculation zone which occurs downstream of the curved edge could explain the asymmetric behaviour of the flow expressed by the variation in wall shear stress values and velocity profile evolution for the positions investigated. The level of residual contamination observed at the lower part of tested pieces of equipment, as in the straight pipes and sudden or gradual contractions, was explained by this effect. It was also shown that certain equipment, such as sudden or gradual contractions or expansions, can induce a flow disturbance and thus affect spore removal from the surface of elements. Velocity profiles obtained by an ultrasonic Doppler velocimetry allowed the flow behaviour after these hydraulic accidents to be explained.
Thierry Benezech - One of the best experts on this subject based on the ideXlab platform.
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Role of mechanical vs. chemical action in the removal of adherent Bacillus spores during CIP procedures
Food Microbiology, 2013Co-Authors: Christine Faille, Thierry Benezech, W. Blel, A. Ronse, G. Ronse, M. Clarisse, Christia SlomiannyAbstract:This study was designed to evaluate the respective roles of mechanical and chemical effectson the removal of Bacillus spores during Cleaning-in-Place. This analysis was performed on 12 strainsbelonging to the B. cereus group (B. cereus, B. anthracis, B. thuringiensis) or to less related Bacillusspecies (B. pumilus, B. licheniformis, B. sporothermodurans, B. subtilis). Adherent spores weresubjected to rinsing-in-Place (mechanical action) and Cleaning-in-Place (mechanical and chemicalresistance to shear was not related to spore surface properties. Conversely, in the presence of NaOH atdetached during CIP and the chemical action greatly depended on the strain. This finding suggests thatchemical action plays the major role during CIP, whose efficacy is significantly governed by the sporesurface chemistry.
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Viability and surface properties of spores subjected to a Cleaning-in-Place procedure: consequences on their ability to contaminate surfaces of equipment
Food Microbiology, 2010Co-Authors: Christine Faille, Yahaya Sylla, Thierry Benezech, Christia Slomianny, Caroline Le Gentil, Yannick LequetteAbstract:This study was designed to evaluate how conditions encountered by spores during Cleaning-in-Place (CIP) procedures affected their surface properties, their viability and ability to contaminate materials. Spores from five Bacillus cereus strains were treated with NaOH at high temperature. Results revealed that high temperatures (exceeding 60 degrees C) and NaOH concentrations (over 0.5%) were required to significantly decrease spore viability (3-5 log decrease). in these conditions, modifications were also clearly observed by microscopy to various surface structures of spores (appendages, exosporium, and especially to the hair-like nap) but also to their coat. Therefore, the ability of culturable spores to adhere decreased for the majority of strains tested. We then demonstrated that spores in suspension in NaOH could adhere to surfaces of a CIP rig and that the contamination level was controlled by flow pattern. Consequently, re-adhesion along the processing line might occur during CIP procedures and this phenomenon must be taken into account when defining Cleaning strategies.
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Hygienic Design: Effect of Hydrodynamics on the Cleanability of a Food Processing Line
AIChE Journal, 2008Co-Authors: W. Blel, P Legentilhomme, Thierry Benezech, J. Legrand, Caroline Le Gentil-lelièvreAbstract:in Wiley interScience (www.interscience.wiley.com). Hydrodynamic effect on the numbers of adhering Bacillus cereus spores before and after Cleaning in Place of part of a dairy processing line was investigated using nonin-trusive flow characterization (local wall shear stresses and velocity profiles measurements). Geometrical changes, like gradual asymmetric pipe contractions and pipe expansions and bends, induce nonhomogeneous distribution of the initial and the residual soiling levels. Moreover, the recirculation zone resulting from the flow detachment after the expansion, allowed to explain the high level of adhered spores downstream of this geometrical change due to the generated shear stresses. The resistance to Cleaning processes in the same zones is mainly governed by the adhesion strength of spores induced by the applied flow rate in the contamination step. Welding and gasket areas, located at different positions in the loop, constituted deposit spots for spores and remained difficult to clean despite high-shear stress forces involved.
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Hygienic design : effect of hydrodynamic on the cleanability of a food processing line
AIChE Journal, 2008Co-Authors: W. Blel, P Legentilhomme, Thierry Benezech, J. Legrand, - Legrand, J., Caroline Le Gentil-lelièvreAbstract:Hydrodynamic effect on the numbers of adhering Bacillus cereus spores before and after Cleaning in Place of part of a dairy processing line was investigated using nonintrusive flow characterization (local wall shear stresses and velocity profiles measurements). Geometrical changes, like gradual asymmetric pipe contractions and pipe expansions and bends, induce nonhomogeneous distribution of the initial and the residual soiling levels. Moreover, the recirculation zone resulting from the flow detachment after the expansion, allowed to explain the high level of adhered spores downstream of this geometrical change due to the generated shear stresses. The resistance to Cleaning processes in the same zones is mainly governed by the adhesion strength of spores induced by the applied flow rate it? the contamination step. Welding and gasket areas, located at different positions in the loop, constituted deposit spots for spores and remained difficult to clean despite high-shear stress forces involved. (C) 2008 American institute of Chemical Engineers.
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Cleaning-in-Place: Modelling of Cleaning Kinetics of Pipes Soiled by Bacillus Spores Assuming a Process Combining Removal and Deposition
Food and Bioproducts Processing, 2002Co-Authors: Claude Lelievre, Christine Faille, Giovanni Antonini, Thierry BenezechAbstract:in food industries, thorough Cleaning -in-Place procedures for the unheated surfaces of food processing equipment are required to ensure the safety of food products by the removal of microorganisms. The aim of this work is to model the removal kinetics of Bacillus spores during a Cleaning-in-Place procedure. These spores were chosen for their occurrence in dairies. The removal of Bacillus cereus spores was found to be strongly dependent on both chemical action (sodium hydroxide), which lowers the adhesion strength of spores onto hard surfaces, and hydrodynamic conditions during Cleaning through wall shear stress. A simple model (first-order reaction) assuming a process combining removal and deposition during Cleaning was detailed and experimentally confirmed. in addition, a significant effect on the effective removal rate constant by both the flow conditions applied during the soiling procedure and applied during Cleaning was observed.
Christine Faille - One of the best experts on this subject based on the ideXlab platform.
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Role of mechanical vs. chemical action in the removal of adherent Bacillus spores during CIP procedures
Food Microbiology, 2013Co-Authors: Christine Faille, Thierry Benezech, W. Blel, A. Ronse, G. Ronse, M. Clarisse, Christia SlomiannyAbstract:This study was designed to evaluate the respective roles of mechanical and chemical effectson the removal of Bacillus spores during Cleaning-in-Place. This analysis was performed on 12 strainsbelonging to the B. cereus group (B. cereus, B. anthracis, B. thuringiensis) or to less related Bacillusspecies (B. pumilus, B. licheniformis, B. sporothermodurans, B. subtilis). Adherent spores weresubjected to rinsing-in-Place (mechanical action) and Cleaning-in-Place (mechanical and chemicalresistance to shear was not related to spore surface properties. Conversely, in the presence of NaOH atdetached during CIP and the chemical action greatly depended on the strain. This finding suggests thatchemical action plays the major role during CIP, whose efficacy is significantly governed by the sporesurface chemistry.
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viability and surface properties of spores subjected to a Cleaning in Place procedure consequences on their ability to contaminate surfaces of equipment
Food Microbiology, 2010Co-Authors: Christine Faille, Yahaya Sylla, Christia Slomianny, Thierry Enezech, Le C Gentil, Yannick LequetteAbstract:Abstract This study was designed to evaluate how conditions encountered by spores during Cleaning-in-Place (CIP) procedures affected their surface properties, their viability and ability to contaminate materials. Spores from five Bacillus cereus strains were treated with NaOH at high temperature. Results revealed that high temperatures (exceeding 60 °C) and NaOH concentrations (over 0.5%) were required to significantly decrease spore viability (3–5 log decrease). in these conditions, modifications were also clearly observed by microscopy to various surface structures of spores (appendages, exosporium, and especially to the hair-like nap) but also to their coat. Therefore, the ability of culturable spores to adhere decreased for the majority of strains tested. We then demonstrated that spores in suspension in NaOH could adhere to surfaces of a CIP rig and that the contamination level was controlled by flow pattern. Consequently, re-adhesion along the processing line might occur during CIP procedures and this phenomenon must be taken into account when defining Cleaning strategies.
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bacterial re contamination of surfaces of food processing lines during Cleaning in Place procedures
Journal of Food Engineering, 2010Co-Authors: Caroline Le Gentil, Yahaya Sylla, Christine FailleAbstract:The possible contamination of surfaces of food processing lines during Cleaning in Place (CIP) procedures was investigated. Experiments were focused on surface contamination of straight pipes and a two-way valve, chosen as an example of complex pieces of equipment. Pipes and a two-way valve were inserted into a CIP rig, at the same time as a series of pipes highly contaminated with spores of three Bacillus cereus strains, with various surfaces properties. Following a CIP procedure, performed in conditions close to those encountered in food industries, the contamination level of the various items was estimated. A significant surface contamination occurring during CIP was evidenced, depending on the spore surface properties. Similarly to previously reported observations, when spores were suspended in optimal adhesion conditions (suspension in water at 20 °C), the re-adhesion phenomenon was controlled by the flow pattern and contamination levels inside the valve were significantly higher than in tubes. Cleaning strategies should therefore take into account the re-adhesion phenomenon to limit the risk of contamination by the process line.
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Bacterial contamination of surfaces of food processing lines during Cleaning in Place procedures
Journal of Food Engineering, 2010Co-Authors: Caroline Le Gentil, Yahaya Sylla, Christine FailleAbstract:The possible contamination of surfaces of food processing lines during Cleaning in Place (CIP) procedures was investigated. Experiments were focused on surface contamination of straight pipes and a two-way valve, chosen as an example of complex pieces of equipment. Pipes and a two-way valve were inserted into a CIP rig, at the same time as a series of pipes highly contaminated with spores of three Bacillus cereus strains, with various surfaces properties. Following a CIP procedure, performed in conditions close to those encountered in food industries, the contamination level of the various items was estimated. A significant surface contamination occurring during CIP was evidenced, depending on the spore surface properties. Similarly to previously reported observations, when spores were suspended in optimal adhesion conditions (suspension in water at 20 degrees C), the re-adhesion phenomenon was controlled by the flow pattern and contamination levels inside the valve were significantly higher than in tubes. Cleaning strategies should therefore take into account the re-adhesion phenomenon to limit the risk of contamination by the process line.
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Viability and surface properties of spores subjected to a Cleaning-in-Place procedure: consequences on their ability to contaminate surfaces of equipment
Food Microbiology, 2010Co-Authors: Christine Faille, Yahaya Sylla, Thierry Benezech, Christia Slomianny, Caroline Le Gentil, Yannick LequetteAbstract:This study was designed to evaluate how conditions encountered by spores during Cleaning-in-Place (CIP) procedures affected their surface properties, their viability and ability to contaminate materials. Spores from five Bacillus cereus strains were treated with NaOH at high temperature. Results revealed that high temperatures (exceeding 60 degrees C) and NaOH concentrations (over 0.5%) were required to significantly decrease spore viability (3-5 log decrease). in these conditions, modifications were also clearly observed by microscopy to various surface structures of spores (appendages, exosporium, and especially to the hair-like nap) but also to their coat. Therefore, the ability of culturable spores to adhere decreased for the majority of strains tested. We then demonstrated that spores in suspension in NaOH could adhere to surfaces of a CIP rig and that the contamination level was controlled by flow pattern. Consequently, re-adhesion along the processing line might occur during CIP procedures and this phenomenon must be taken into account when defining Cleaning strategies.
Jack Legrand - One of the best experts on this subject based on the ideXlab platform.
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application of turbulent pulsating flows to the bacterial removal during a Cleaning in Place procedure part 2 effects on Cleaning efficiency
Journal of Food Engineering, 2009Co-Authors: Walid Lel, P Legentilhomme, Thierry Enezech, Jack Legrand, Le C GentillelievreAbstract:Pulsating turbulent flows effects on Cleaning in Place procedure of straight pipes were investigated for various pulsations parameters (frequency and amplitude) and mean velocities of the flow. Pulsations generation was made with a new system which allows high amplitude of pulsations. Experiments showed the contribution of the different pulsation parameters, in the removal of adhered bacterial spores, in addition to the effect of the mean velocity of the flow. A high level of the Cleaning rate is observed despite the reduction of the magnitude of the mean velocity. This result can be explained by the effect of the two pulsations parameters (amplitude and frequency) which ensure a high wall shear rate. The study of the Cleaning kinetics has shown the increase of the removal constant rate of spores using pulsed flow in comparison with the use of a steady turbulent flow.
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application of turbulent pulsating flows to the bacterial removal during a Cleaning in Place procedure part 1 experimental analysis of wall shear stress in a cylindrical pipe
Journal of Food Engineering, 2009Co-Authors: Walid Lel, Thierry Enezech, Le C Gentillelievre, Jack Legrand, P LegentilhommeAbstract:Abstract The effects of pulsating turbulent flows on wall shear stress components were investigated in a straight pipe using the non-intrusive electrochemical method. Experiments were made using a new pulsation generator system which allows high amplitude pulsations in addition to a perfect stability of the installation. Maximum pulsation frequency equal to 2.86 Hz is used, above which fluid inertia dominates over most part of the flow field. Analysis showed that pulsating flows induce an increase of local velocity gradient at the wall pipe. This result is explained by the periodic renewal of the boundary layers. Spectral analysis showed high increasing rates of the fluctuation energy for the different pulsating conditions in comparison with a steady flow. The tested condition involving a recirculation flow induced a modification in the energy dissipation cascade, which can be explained by the redistribution of eddies size near the wall.
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effect of flow arrangement on the removal of bacillus spores from stainless steel equipment surfaces during a Cleaning in Place procedure
Chemical Engineering Science, 2007Co-Authors: Walid Lel, P Legentilhomme, Thierry Enezech, Jack Legrand, Caroline Le GentillelievreAbstract:influence of local wall shear stresses measured at different circumferential positions of a series of various piping elements (such as gradual or sudden contractions or expansions) on the removal of Bacillus spores during a Cleaning in Place (CIP) procedure was studied. The variation in residual contamination levels observed for the three tangential positions analysed was induced by the flow disturbance caused by various interacting geometric elements, essentially the bend localised upstream of the tested pipes. The recirculation zone which occurs downstream of the curved edge could explain the asymmetric behaviour of the flow expressed by the variation in wall shear stress values and velocity profile evolution for the positions investigated. The level of residual contamination observed at the lower part of tested pieces of equipment, as in the straight pipes and sudden or gradual contractions, was explained by this effect. It was also shown that certain equipment, such as sudden or gradual contractions or expansions, can induce a flow disturbance and thus affect spore removal from the surface of elements. Velocity profiles obtained by an ultrasonic Doppler velocimetry allowed the flow behaviour after these hydraulic accidents to be explained.
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Cleaning in Place: Effect of local wall shear stress variation on bacterial removal from stainless steel equipment
Chemical Engineering Science, 2002Co-Authors: Claude Lelievre, Cécile Gaucher, P Legentilhomme, Christine Faille, Jack Legrand, Thierry BenezechAbstract:Local wall shears stress analysis as well as cleanability experiments on different pieces of equipment in various circuit arrangements were performed. Pieces of equipment used in this work, stainless steel made, were representative of production lines: straight pipes of different diameters, sudden or gradual contraction or expansion pipes. Local wall shear stress values, obtained by an electrochemical method, were shown to be influenced by the loop arrangement. Geometry as the gradual expansion pipe had an effect on the upstream straight pipe where the wall shear stress values were two times lower than in other configurations as with a sudden expansion. in sudden geometry, the bacterial removal during Cleaning was improved by the increase of the flow rate, corresponding to the increase of the mean local wall shear stress. However, in gradual expansion or contraction pipe, cleanability was not improved by the increase of flow rate. The effect of the mean wall shear stress on the removal has been confirmed. Moreover, this work demonstrated a clear positive effect of an increase of the fluctuation rate on the spore detachment. Low mean wall shear stress zones as in sudden expansion (around 0.15 Pa) could be cleanable because of the high fluctuation rate (around 21%). These results underline the importance of the design and the flow configuration. © 2002 Elsevier Science Ltd. All rights reserved.
Walid Lel - One of the best experts on this subject based on the ideXlab platform.
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application of turbulent pulsating flows to the bacterial removal during a Cleaning in Place procedure part 2 effects on Cleaning efficiency
Journal of Food Engineering, 2009Co-Authors: Walid Lel, P Legentilhomme, Thierry Enezech, Jack Legrand, Le C GentillelievreAbstract:Pulsating turbulent flows effects on Cleaning in Place procedure of straight pipes were investigated for various pulsations parameters (frequency and amplitude) and mean velocities of the flow. Pulsations generation was made with a new system which allows high amplitude of pulsations. Experiments showed the contribution of the different pulsation parameters, in the removal of adhered bacterial spores, in addition to the effect of the mean velocity of the flow. A high level of the Cleaning rate is observed despite the reduction of the magnitude of the mean velocity. This result can be explained by the effect of the two pulsations parameters (amplitude and frequency) which ensure a high wall shear rate. The study of the Cleaning kinetics has shown the increase of the removal constant rate of spores using pulsed flow in comparison with the use of a steady turbulent flow.
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application of turbulent pulsating flows to the bacterial removal during a Cleaning in Place procedure part 1 experimental analysis of wall shear stress in a cylindrical pipe
Journal of Food Engineering, 2009Co-Authors: Walid Lel, Thierry Enezech, Le C Gentillelievre, Jack Legrand, P LegentilhommeAbstract:Abstract The effects of pulsating turbulent flows on wall shear stress components were investigated in a straight pipe using the non-intrusive electrochemical method. Experiments were made using a new pulsation generator system which allows high amplitude pulsations in addition to a perfect stability of the installation. Maximum pulsation frequency equal to 2.86 Hz is used, above which fluid inertia dominates over most part of the flow field. Analysis showed that pulsating flows induce an increase of local velocity gradient at the wall pipe. This result is explained by the periodic renewal of the boundary layers. Spectral analysis showed high increasing rates of the fluctuation energy for the different pulsating conditions in comparison with a steady flow. The tested condition involving a recirculation flow induced a modification in the energy dissipation cascade, which can be explained by the redistribution of eddies size near the wall.
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effect of flow arrangement on the removal of bacillus spores from stainless steel equipment surfaces during a Cleaning in Place procedure
Chemical Engineering Science, 2007Co-Authors: Walid Lel, P Legentilhomme, Thierry Enezech, Jack Legrand, Caroline Le GentillelievreAbstract:influence of local wall shear stresses measured at different circumferential positions of a series of various piping elements (such as gradual or sudden contractions or expansions) on the removal of Bacillus spores during a Cleaning in Place (CIP) procedure was studied. The variation in residual contamination levels observed for the three tangential positions analysed was induced by the flow disturbance caused by various interacting geometric elements, essentially the bend localised upstream of the tested pipes. The recirculation zone which occurs downstream of the curved edge could explain the asymmetric behaviour of the flow expressed by the variation in wall shear stress values and velocity profile evolution for the positions investigated. The level of residual contamination observed at the lower part of tested pieces of equipment, as in the straight pipes and sudden or gradual contractions, was explained by this effect. It was also shown that certain equipment, such as sudden or gradual contractions or expansions, can induce a flow disturbance and thus affect spore removal from the surface of elements. Velocity profiles obtained by an ultrasonic Doppler velocimetry allowed the flow behaviour after these hydraulic accidents to be explained.