The impact of canister geometry on chemical biological radiological and nuclear filter performance: A computational fluid dynamics analysis

Wood, Samuel G. A.; Chakraborty, Nilanjan; Smith, Martin W.; Summers, Mark; Brewer, Stuart A.

doi:10.1080/15459624.2018.1533674

Cited by 6 publications

(2 citation statements)

References 13 publications

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“…The numerical model used here has been previously used to give good predictions of pressure drop across an activated carbon bed …”

Section: Experimental Methods and Resultsmentioning

confidence: 99%

“…30 The numerical model used here has been previously used to give good predictions of pressure drop across an activated carbon bed. 31 Mesh Independence. Mesh independence has been ensured by assessing the initial depth of penetration into the bed and the speed of the advancing contaminated for three representative cases.…”

Section: ■ Experimental Methods and Resultsmentioning

confidence: 99%

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Combined Experimental and Numerical Investigation of Linear Driving Force Kinetics in Small Activated Carbon Beds

Wood

Chakraborty

Smith

et al. 2019

Ind. Eng. Chem. Res.

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A numerical model has been developed with the intention of better understanding the relationship between flow characteristics and adsorption behavior in small activated carbon beds. The model uses the Dubinin–Radushkevich adsorption isotherm with Linear Driving Force kinetics and has been validated against experimental data for the breakthrough of cyclohexane. Simulations have been carried out varying the inlet flow rate and the adsorption kinetic constant. The adsorption behavior has been analyzed by assessing the furthest point into the bed that a threshold concentration of a contaminant could be seen in the vapor phase. It was seen in all cases that the adsorption was a two-stage process with a rapid initial penetration into a certain bed depth followed by a relatively slow gradual progression of the front through the bed over time. The initial distance penetrated into the bed has been seen to be inversely proportional to the kinetic constant, the same trend as predicted from a plug flow mass balance analysis. The rate of steady front advancement after this showed a slight tendency to increase with decreasing adsorption kinetics, compared to the expected plug flow speed.

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“…The numerical model used here has been previously used to give good predictions of pressure drop across an activated carbon bed …”

Section: Experimental Methods and Resultsmentioning

confidence: 99%

Section: ■ Experimental Methods and Resultsmentioning

confidence: 99%

Combined Experimental and Numerical Investigation of Linear Driving Force Kinetics in Small Activated Carbon Beds

Wood

Chakraborty

Smith

et al. 2019

Ind. Eng. Chem. Res.

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Design and Integration of a Gas Sensor Module that Indicates the End of Service Life of a Gas Mask Canister

Moon

Lee

Min

et al. 2021

Adv Materials Technologies

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adsorbent material has limited adsorption capacity, the chemical cartridge or the filter needs to be replaced before the adsorption capacity is exceeded. End of service life indicator (ESLI), a system that informs the users as to when to replace the filter, has been widely employed in consumer products such as air conditioners and water/air purifiers. For these products, replacing the filters on time is advisable but not mandatory. By contrast, for the filtration of toxic gases, such as chemical warfare agents (CWAs) and toxic industrial chemicals (TICs), the expired filter must be promptly replaced for the safety of the users. Developing an ESLI in those systems, however, has been sluggish. [2] ESLI for filtration of CWAs is not available, and ESLI developed for canisters against TICs uses colorimetric sensors that are slow and have low sensitivity as compared to electronic sensors. Occupational Safety and Health Administration (Department of Labor, USA) presents a guideline for replacing the filter based on mathematical models, [3] whose input parameters are the type of gases, and their concentrations, temperature, humidity, flow rate, etc. Application of such models, however, is not practical as the parameters not only are difficult to measure but also vary In a filtration system, a chemical cartridge packed with porous adsorbents needs to be replaced when its maximum adsorption capacity is exceeded. An end of service life indicator (ESLI) informs when to replace the cartridge. However, ESLI technology for filtration of toxic gases is overlooked despite high toxicity of the gases even at low concentrations. In this study, a real-time ESLI is demonstrated for filtration of chemical warfare agents by inserting four chemiresistors made of carbon nanotubes into the adsorbent layer of a canister for gas masks. The sensors are installed on a flexible printed circuit board with a 3D structure to minimize the channeling effect in the canister. As the breakthrough of dimethyl methylphosphonate, a nerve agent simulant, progresses in the canister, the resistance of the sensors increases sequentially with time. The inflection points in the responses from sensors designated #1-#4 indicate that the percentage of remaining service life is 75%, 50%, 25%, and 0%, respectively. The ESLI potentially applies to a wide range of toxic gases and cartridge designs, regardless of the sensitivity and selectivity of the sensors, as supported by the breakthrough of ammonia as well as the results from a smaller canister.

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Modelling the stochastic nature of porosity in a respirator canister using computational fluid dynamics

et al. 2020

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A model has been developed to represent the stochastic nature of the activated carbon bed within a generic chemical biological radiological and nuclear (CBRN) respirator canister. The porous region is subdivided into discrete sections which are assigned a porosity based on their radial position according to a longitudinally‐averaged porosity model, and then perturbed by some amount according to a Gaussian distribution. The porosity model was used in Reynolds‐averaged Navier‐Stokes (RANS) simulations in order to assess the impacts that the choice of section size and the porosity variation would have on the pressure drop and residence time distribution. It was shown for small section sizes that increasing porosity variation would increase pressure drop and minimum residence time in the carbon bed, while decreasing the average residence time. As the section sizes became larger the reverse trend was seen as a greater extent of flow channelling throughout the bed became apparent. For the given domain size, there was an upper limit to the section size, beyond which statistical convergence could not be guaranteed. It was also shown that for section sizes close to the particle diameter, the results would depend only on the ratio of section size to porosity variation, reducing the porosity model to a single parameter. A few selected cases were simulated at higher flow rates, where the previously mentioned trends were seen to persist.

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The impact of canister geometry on chemical biological radiological and nuclear filter performance: A computational fluid dynamics analysis

Cited by 6 publications

References 13 publications

Combined Experimental and Numerical Investigation of Linear Driving Force Kinetics in Small Activated Carbon Beds

Combined Experimental and Numerical Investigation of Linear Driving Force Kinetics in Small Activated Carbon Beds

Design and Integration of a Gas Sensor Module that Indicates the End of Service Life of a Gas Mask Canister

Modelling the stochastic nature of porosity in a respirator canister using computational fluid dynamics

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