The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Shekar Viswanathan - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Airflow Around a Variable Volume/Constant Face Velocity Fume Cupboard
American Industrial Hygiene Association Journal, 2020Co-Authors: Shekar ViswanathanAbstract:Three-dimensional models of a variable volume/constant face velocity Fume hood were developed and numerically solved to study the effect of the sash opening and rated face velocity on the flow patterns, especially in the exposure area of a person standing in front of the Fume hood. These flow details are important in assessing the containment performance of the Fume hood. For this study, fully turbulent flow was assumed to enter through the front hood window and exit through the exhaust duct. The finite-difference, control-volume technique, and standard k-∊ models were employed and solved together with the equations for the conservation of mass and momentum using FLUENT/UNS version 4.2 to obtain the flow solutions. Unobstructed flow cases, as well as the simplified two-dimensional scenarios, also were investigated for comparison. Results indicated that there is no occurrence of recirculation leading to concentration buildup within the region between the person and Fume hood entrance Also, in conformance w...
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numerical simulation of airflow around a variable volume constant face velocity Fume Cupboard
American Industrial Hygiene Association Journal, 2001Co-Authors: Shekar ViswanathanAbstract:Three-dimensional models of a variable volume/constant face velocity Fume hood were developed and numerically solved to study the effect of the sash opening and rated face velocity on the flow patterns, especially in the exposure area of a person standing in front of the Fume hood. These flow details are important in assessing the containment performance of the Fume hood. For this study, fully turbulent flow was assumed to enter through the front hood window and exit through the exhaust duct. The finite-difference, control-volume technique, and standard k-∊ models were employed and solved together with the equations for the conservation of mass and momentum using FLUENT/UNS version 4.2 to obtain the flow solutions. Unobstructed flow cases, as well as the simplified two-dimensional scenarios, also were investigated for comparison. Results indicated that there is no occurrence of recirculation leading to concentration buildup within the region between the person and Fume hood entrance Also, in conformance w...
D B Ingham - One of the best experts on this subject based on the ideXlab platform.
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effects of a ventilation duct on the performance of a Fume Cupboard
International conference on air distribution in rooms, 1998Co-Authors: M J Trevelyan, L Elliott, D B InghamAbstract:When a Fume Cupboard is placed in a room with a ventilation duct, the air movement inside and around the Fume Cupboard is fully three-dimensional turbulent flow. However, in order to understand the fluid flow away from the Fume Cupboard a much simpler model can be used. This leads to a steady 2D model, with the computational domain including only the sash of the Fume Cupboard, the room and the entrance into the ventilation duct. In this paper we have used both the k-e turbulence model and the wall function technique to calculate the steady 2D turbulent fluid flow In addition, a mathematical technique has been employed to map the simpler model onto the upper half of the complex plane, so that the complex potential can be found using a source and a sink on the real axis to represent the ventilation inlet and the exhaust outlet of the room, respectively The objective of this paper is to reduce the cpu time by restricting the computational domain to a region which only includes the Fume Cupboard and a small region outside. We establish from a modified version of the potential flow a solution which we can use near the Fume Cupboard as a specified velocity boundary condition whilst solving the turbulent fluid flow model within the Fume Cupboard.
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effect of the location of the exhaust duct an exterior obstruction and handle on the air flow inside and around a Fume Cupboard
Annals of Occupational Hygiene, 1996Co-Authors: Peixin Hu, D B InghamAbstract:In order to be able to reduce the leakage of contaminant out of a Fume Cupboard it is first necessary to investigate the detailed fluid flow patterns inside and around the Fume Cupboard. Because of the difficulties and expense of performing these experiments, in this paper a computational fluid dynamics approach has been used. The aim of the work is to investigate the potential of various factors which cause the leakage of contaminant from the Fume Cupboard. In particular the effect of: (i) the location of the exhaust outlet on the roof of the Fume Cupboard; (ii) exterior obstructions of different shapes and sizes in front of the Fume Cupboard; and (iii) the Fume Cupboard handle, which takes various shapes and positions, in laminar and turbulent fluid flow both inside and around the Fume Cupboard. From the fluid flows observed, for each configuration, their importance in relation to future experimental work to be performed and possible new designs of Fume Cupboards is discussed. Wherever possible comparisons have been made with existing experimental data and in all cases good qualitative agreement is available.
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a mathematical model for the air flow around a worker near a Fume Cupboard
Annals of Occupational Hygiene, 1992Co-Authors: D B Ingham, Y YuanAbstract:This paper presents the results of a two-dimensional mathematical model for the flow of air past a worker modelled as an elliptical cylinder, into an open Fume Cupboard. The Boundary Element method is used to obtain the fliud velocity away from the surface of the solid boundaries, and everywhere on the surface of the ellipse the tangential velocity is then obtained using B-splines
Graham P Nicholson - One of the best experts on this subject based on the ideXlab platform.
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a simple method for Fume Cupboard performance assessment
Annals of Occupational Hygiene, 2000Co-Authors: Graham P Nicholson, Raymond P Clark, Fred Grover, Mervyn L De CalcinagoffAbstract:Abstract The performance of a Fume Cupboard is determined by a complex interaction of factors which are time consuming and expensive to determine. This paper describes a simple and practical means of ranking, and assessing Fume Cupboard installations that can help to discharge managerial responsibility for a ‘safe’ environment. The method also gives an economically viable and technically defensible system for assessing Fume Cupboard performance as part of upgrading exercises or performance audits. The assessment strategy uses flow visualisation techniques and measurements of inflow air velocity as well as overall condition evaluation to rank performance and identify poor performing Cupboards. The method has been used to carry out a condition and performance survey of 199 Fume Cupboards, both aerodynamic and box-type designs, in an academic institution. The results of this survey are presented which not only highlight performance characteristics but also provide insights into user attitudes and knowledge of Fume Cupboard operation and performance. It is suggested that surveys such as this could be helpful in training programmes for laboratory workers to enable them to optimise the use of Fume Cupboards.
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computational fluid dynamics as a method for assessing Fume Cupboard performance
Annals of Occupational Hygiene, 2000Co-Authors: Graham P Nicholson, Raymond P Clark, Mervyn L De CalcinagoffAbstract:A commercially available computational fluid dynamic (CFD) software program, specific for HVAC systems, was used to study the performance of an aerodynamic Fume Cupboard. The numerical results showed good qualitative agreement with physical measurements giving confidence in the CFD model to simulate and predict overall Fume Cupboard performance. However, there were some quantitative diAerences specifically around ‘aerodynamic’ features that could not be accurately simulated by the software code. The CFD model was clearly able to demonstrate diAerences in performance between good and bad Cupboard designs, and show the importance of using rear baCes and lipfoils. It also showed the importance of good design features when a ‘worker’ was standing against the front edge or when there were draughts in front of the aperture. The computer model was used to simulate the gas tracer containment test method described in BS 7258 (1994) [Laboratory Fume Cupboards], and had a much greater sensitivity than the recommended physical measuring instruments. The results given in this paper demonstrate the potential for using a commercially available software package for the optimisation of Fume Cupboard design and testing. It also indicates the economy of using CFD compared with building a prototype and testing a model. 7 2000 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved.
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Theoretical and Practical Comparison of the Potassium Iodide Tracer Method (KI–Discus) for Assessing the Containment Efficiency of Fume Cupboards with the Gas Tracer Method Described in BS 7258: 1994: Part 4
Annals of Occupational Hygiene, 1999Co-Authors: Graham P Nicholson, Raymond P Clark, Mervyn L. De Calcina-goffAbstract:Abstract Attempts have been made by manufacturing groups, health and safety legislators and national and international standards bodies to standardise containment testing strategies for open fronted containment systems. It is important that all the strategies and testing methods used should yield comparable results. However, there are a number of test methodologies that have not been standardised or correlated, and the results between them cannot be compared. Manufacturers of contamination control equipment have the expense of testing by varying methods in different countries where standards apply. Ultimately, it is hoped that there will be either one standard method for testing all open fronted containment facilities, or, if there are different methods, that they yield results which can be compared. In this paper a theoretical and practical comparison is made of the KI–Discus test method for assessing Fume Cupboard performance and the tracer gas method recommended in BS 7258, 1994 : Part 4. Comparison of these two methods for testing Fume Cupboards was found not to be practicable due to fundamental differences in 1) the philosophy of the tests, 2) the tracers used, 3) their method of generation, 4) the disposition of equipment and 5) the sampling methods. It is demonstrated that the KI method is more sensitive than the gas method and that the philosophy of the KI method is to detect actual leakage whereas, the gas method detects potential leakage (viz. contamination reaching the plane of the aperture).
Mervyn L De Calcinagoff - One of the best experts on this subject based on the ideXlab platform.
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a simple method for Fume Cupboard performance assessment
Annals of Occupational Hygiene, 2000Co-Authors: Graham P Nicholson, Raymond P Clark, Fred Grover, Mervyn L De CalcinagoffAbstract:Abstract The performance of a Fume Cupboard is determined by a complex interaction of factors which are time consuming and expensive to determine. This paper describes a simple and practical means of ranking, and assessing Fume Cupboard installations that can help to discharge managerial responsibility for a ‘safe’ environment. The method also gives an economically viable and technically defensible system for assessing Fume Cupboard performance as part of upgrading exercises or performance audits. The assessment strategy uses flow visualisation techniques and measurements of inflow air velocity as well as overall condition evaluation to rank performance and identify poor performing Cupboards. The method has been used to carry out a condition and performance survey of 199 Fume Cupboards, both aerodynamic and box-type designs, in an academic institution. The results of this survey are presented which not only highlight performance characteristics but also provide insights into user attitudes and knowledge of Fume Cupboard operation and performance. It is suggested that surveys such as this could be helpful in training programmes for laboratory workers to enable them to optimise the use of Fume Cupboards.
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computational fluid dynamics as a method for assessing Fume Cupboard performance
Annals of Occupational Hygiene, 2000Co-Authors: Graham P Nicholson, Raymond P Clark, Mervyn L De CalcinagoffAbstract:A commercially available computational fluid dynamic (CFD) software program, specific for HVAC systems, was used to study the performance of an aerodynamic Fume Cupboard. The numerical results showed good qualitative agreement with physical measurements giving confidence in the CFD model to simulate and predict overall Fume Cupboard performance. However, there were some quantitative diAerences specifically around ‘aerodynamic’ features that could not be accurately simulated by the software code. The CFD model was clearly able to demonstrate diAerences in performance between good and bad Cupboard designs, and show the importance of using rear baCes and lipfoils. It also showed the importance of good design features when a ‘worker’ was standing against the front edge or when there were draughts in front of the aperture. The computer model was used to simulate the gas tracer containment test method described in BS 7258 (1994) [Laboratory Fume Cupboards], and had a much greater sensitivity than the recommended physical measuring instruments. The results given in this paper demonstrate the potential for using a commercially available software package for the optimisation of Fume Cupboard design and testing. It also indicates the economy of using CFD compared with building a prototype and testing a model. 7 2000 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved.
Frederik C. Krebs - One of the best experts on this subject based on the ideXlab platform.
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Roll and roll-to-roll process scaling through development of a compact flexo unit for printing of back electrodes
Solar Energy Materials and Solar Cells, 2015Co-Authors: Henrik F. Dam, Thomas R. Andersen, Morten V. Madsen, Thomas K. Mortensen, Mads F. Pedersen, Uffe Nielsen, Frederik C. KrebsAbstract:We report manufacture of fully printed and coated polymer solar cells on a small scale roll-to-roll coater representing the intermediate scale between laboratory and pilot scale. We highlight the enormous span in scale between the laboratory scale and the intended industrial scale by a factor of >100.000 and detail how this enormous scale must be covered by equipment that follow the scale. Especially the intermediate scale between equipment that can fit inside a Fume Cupboard and the typical pilot equipment with a footprint having the size of a large room presents a challenge that comprises some of the most critical steps in the scaling process. We describe the development of such a machine that comprise web guiding, tension control and surface treatment in a compact desk size that is easily moved around and also detail the development of a small cassette based flexographic unit for back electrode printing that is parsimonious in terms of ink usage and more gentle than laboratory scale flexo units where the foil transport is either driven by the flexo unit or the flexo unit is driven by the foil transport. We demonstrate fully operational flexible polymer solar cell manufacture using this new roll and roll-to-roll (R3) approach and compare with the existing methods.
