2024 |
Chowdhury R, Mainul Hoque M, Evans G, Honeyands T, Monaghan BJ, Scimone D, Mitra S, 'Impact dynamics and solidification behaviour of a molten droplet on a flat surface at different Weber numbers', Experimental Thermal and Fluid Science, 154 111156-111156 (2024)
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2024 |
Wang A, Banks E, Evans G, Mitra S, 'Effect of surfactant concentration and surface loading on the dynamics of a rising particle-laden bubble', Chemical Engineering Science, 288 (2024) [C1]
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Nova |
2024 |
Dutta N, Mitra S, Nirmalkar N, 'Understanding the Role of Surface Charge on Nanobubble Capillary Bridging during Particle Particle Interaction', Langmuir, 40 4475-4488 (2024)
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2024 |
Mitra S, Hoque MM, O'Dea D, Honeyands T, 'Understanding cohesive zone behaviour of blast furnace based on computed tomography flow modelling in a fused bed of ferrous and coke particles', Powder Technology, 439 (2024) [C1]
Performance of ironmaking blast furnace systems critically depends on the permeability of the cohesive zone which involves flow of reducing gas through a packed bed of fused ferro... [more]
Performance of ironmaking blast furnace systems critically depends on the permeability of the cohesive zone which involves flow of reducing gas through a packed bed of fused ferrous and coke particles at high temperature. This study systematically investigated the effect of operating temperature on bed permeability for two different ferrous burdens - pellets, and pellets-sinter mixture supported on coke particles. To quantify the structural changes in the bed, interrupted tests at various temperatures were conducted and bed porosity was estimated using synchrotron X-ray computed tomography (CT) technique. Bed porosity showed decreasing trends with increasing temperature. A CT image based computational flow dynamics (CFD) model was developed which showed linearly decreasing trends of bed permeability parameter with increasing temperature indicating a significant loss of bed permeability in the high temperature cases. This behaviour was more pronounced for the pure pellet case compared to the mixed burden case.
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2024 |
Hoque MM, Mitra S, Evans G, 'Bubble size distribution and turbulence characterization in a bubbly flow in the presence of surfactant', Experimental Thermal and Fluid Science, 155 (2024) [C1]
This study aimed to quantify the less explored complex multiphase hydrodynamics of a bubble swarm in the presence of surfactant which is the key to flotation process widely used i... [more]
This study aimed to quantify the less explored complex multiphase hydrodynamics of a bubble swarm in the presence of surfactant which is the key to flotation process widely used in the resources and environmental engineering applications. Experiments were conducted in a rectangular column (cross-section: 100 mm × 100 mm) in batch mode by varying the gas flux (0.02 to and 0.08 cm/s) in the presence of an anionic surfactant sodium dodecyl sulphate (5 to 15 ppm). High-speed imaging was then used to visualise the unsteady bubble plume dispersion behaviour and estimate the bubble size distribution (BSD) which showed a reduction in the mean bubble size with the increasing gas flux and surfactant concentration. Next, particle image velocimetry (PIV) was utilised to measure the instantaneous velocity field which was used to determine the turbulence characteristics. It was shown that the bubble plume contributes to significant anisotropy in the flow field which increased in the higher surfactant concentration and gas flux cases. The energy containing turbulence length scale was characterized by the integral length scale, which was observed to increase linearly with both the gas flux and surfactant concentration. Also, the local turbulence energy dissipation rate exhibited a strong linear correlation with the bubble surface area flux parameter. In the presence of surfactant, the turbulence energy spectrum of the system exhibited a less steep slope in the inertial subrange regime compared to the Kolmogorov -5/3 slope. The spectrum also showed a leftward shift indicating energy addition to the larger turbulence length scales which was reflected in the formation of large recirculation zones around the bubble plume.
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2024 |
Barrett N, Mitra S, Copland E, Chew S, O Dea D, Honeyands T, 'Changes in Microscale Liquid Formation in Lump and Sinter Mixed Burden Softening and Melting Tests with the Addition of Hydrogen', Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science, (2024) [C1]
Abstract: With the movement toward hydrogen-enriched blast furnace operation to lower greenhouse gas emissions, ferrous burden design must be reconsidered to optimize furnace perm... [more]
Abstract: With the movement toward hydrogen-enriched blast furnace operation to lower greenhouse gas emissions, ferrous burden design must be reconsidered to optimize furnace permeability. Increasing the ratio of direct charge lump ore in the ferrous burden also presents an opportunity to lessen the emissions associated with the production of sinter and pellets. Under traditional blast furnace conditions, lump ore usage is improved by mixing it with the sinter in the burden to promote their favorable high-temperature interactions (both chemical and physical). As such, mechanistic changes to the interaction must be understood to optimize burden design, including for future operations with hydrogen addition. In this study, liquid formation in both the metallic and oxide components of ferrous burdens is microscopically investigated. Oxide liquid and solid phase stability at the interfaces of dissimilar burdens are visualized using a novel mapping technique, and metallic iron is etched to reveal microstructures indicative of carbon. Results indicate that the inclusion of hydrogen promotes the gas carburization of metallic iron in sinter, but not lump. It was concluded that mixed burden softening and melting performance with hydrogen addition were improved through the addition of lump in two ways: the highly metallic lump particles provide structural support for the collapsing sinter bed and also suppress the formation of early liquid slag from the sinter. Graphical Abstract: (Figure presented.).
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2023 |
Wang A, Evans G, Mitra S, 'A review of bubble surface loading and its effect on bubble dynamics', MINERALS ENGINEERING, 199 (2023) [C1]
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Nova |
2023 |
Barrett N, Mitra S, Doostmohammadi H, O Dea D, Zulli P, Chew S, Honeyands T, 'Development of softening and melting testing conditions simulating blast furnace operation with hydrogen injection', Ironmaking & Steelmaking, 50 1248-1259 (2023) [C1]
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Nova |
2023 |
Hoque MM, Joshi JB, Evans GM, Mitra S, 'A critical analysis of turbulence modulation in particulate flow systems: a review of the experimental studies', Reviews in Chemical Engineering, 0 [C1]
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2023 |
Barrett N, Mitra S, Chew S, O Dea D, Honeyands T, 'Effect of Hydrogen Addition on Softening and Melting Performance of Lump and Sinter Mixed Burden', ISIJ International, 63 1626-1636 (2023) [C1]
Hydrogen-enriched blast furnace (BF) operation is currently being assessed to mitigate greenhouse gas emissions while the steelmaking industry transitions to low carbon emission t... [more]
Hydrogen-enriched blast furnace (BF) operation is currently being assessed to mitigate greenhouse gas emissions while the steelmaking industry transitions to low carbon emission technologies. Increasing the usage of lump ore in the BF also presents opportunity to decrease carbon emissions, as it can be directly charged to the furnace without agglomeration. Use of lump ore in modern blast furnace operations is facilitated by high temperature interactions with sinter. With more emphasis on hydrogen enrichment in BF operations, the behaviour of lump and sinter mixed burdens must be characterised under new conditions. In this study, 15% hydrogen is added to the standard gas conditions of a Softening and Melting (S&M) apparatus (replacing nitrogen). Analysis of auxiliary reactions such as the Boudouard Reaction and the Water-Gas Shift Reaction is presented and their impact on burden reduction and performance assessed. Results indicate that with the inclusion of hydrogen, the performance of sinter burden deteriorates, while lump burden shows significant improvement. Interaction between sinter and lump still occurred with the inclusion of hydrogen in the gas, and the mixed burden behaviour of 20% lump and 80% sinter fell between that of the individual burdens. From interrupted experiments, it is noted at high degrees of reduction, the lump burden forms a solid metallic layer which maintains its interparticle voidage at high temperatures, supressing exudation of liquid slag.
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Nova |
2022 |
Barrett N, Mitra S, Doostmohammadi H, O'Dea D, Zulli P, Chew S, Honeyands T, 'Assessment of Blast Furnace Operational Constraints in the Presence of Hydrogen Injection', ISIJ INTERNATIONAL, 62 1168-1177 (2022) [C1]
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Nova |
2022 |
Wang A, Hoque MM, Evans G, Mitra S, 'Effect of turbulence dispersion on bubble-particle collision efficiency', Minerals Engineering, 177 107374-107374 (2022) [C1]
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Nova |
2022 |
Hoque MM, Moreno-Atanasio R, Doroodchi E, Joshi JB, Evans GM, Mitra S, 'Dynamics of a single bubble rising in a quiescent medium', Experimental Thermal and Fluid Science, 132 (2022) [C1]
In the present work, an experimental analysis was performed to characterise the flow field around a single bubble of different diameters ~ 2.77¿3.53 mm) rising in a quiescent medi... [more]
In the present work, an experimental analysis was performed to characterise the flow field around a single bubble of different diameters ~ 2.77¿3.53 mm) rising in a quiescent medium aiming to determine the effect of bubble size on kinetic energy distribution. The velocity field was measured using a non-intrusive particle image velocimetry (PIV) technique and kinetic energy spectrum was determined in both transverse and longitudinal directions applying a Fast Fourier Transformation (FFT). Both small- and large-scale motions of the flow field were identified and separated using a discreate wavelet transformation (DWT) method. It was found that the energy spectrum of the large-scale motions depended on the bubble size while the small-scale energy spectrum was nearly independent of it. The slopes of the energy spectrum were found to be close to -5/3 and -3 for the large- and small-scale regimes, respectively and the transition of slope was observed to occur at the wavenumber corresponding to the bubble diameter. Using the measured velocity field data, a turbulence kinetic energy (TKE) budget analysis was performed involving five components namely kinetic energy production, turbulent transport, pressure diffusion, viscous diffusion, and energy dissipation. Overall, it was observed that in the vicinity of bubble surface, turbulence production term was not entirely balanced by the dissipation term; and turbulent transport and pressure diffusion term also had significant contributions.
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Nova |
2022 |
Wang A, Hoque MM, Evans G, Mitra S, 'Determining collision efficiency in multi-bubble-particle systems in presence of turbulence', Minerals Engineering, 189 107889-107889 (2022) [C1]
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Nova |
2022 |
Hoque MM, Doroodchi E, Jameson GJ, Evans GM, Mitra S, 'Numerical estimation of critical local energy dissipation rate for particle detachment from a bubble-particle aggregate captured within a confined vortex', Minerals Engineering, 180 (2022) [C1]
In flotation, interactions of bubble-particle aggregates with turbulent flow structures in the liquid medium result in particle detachment. This study aims to simulate this phenom... [more]
In flotation, interactions of bubble-particle aggregates with turbulent flow structures in the liquid medium result in particle detachment. This study aims to simulate this phenomenon involving a bubble-particle aggregate (bubble diameter ~ 3 mm and particle diameter ~ 314 µm) interacting with a turbulent flow structure manifested as a confined vortex in a square cavity connected to a square cross-section channel. An interface resolved three dimensional (3D) computational fluid dynamics (CFD) model was developed to quantify the bubble-vortex interaction dynamics over a range of channel Reynolds numbers. The CFD model produced a good agreement with the experimentally measured vorticity magnitude, local energy dissipation rate, and bubble motion. It was shown that a bubble-particle aggregate could be captured within the vortex by suitably varying the channel Reynolds number, eventually leading to particle detachment. A separate force balance analysis was performed to determine a criterion for particle detachment utilising the CFD model predicted vorticity and local energy dissipation rate. It was shown that a critical local energy dissipation rate ~ 1.59 m2/s3 was required for particle detachment to occur, which was also verified experimentally.
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Nova |
2022 |
Singh T, Mitra S, O dea D, Knuefing L, Honeyands T, 'Quantification of Resistance and Pressure Drop at High Temperature for Various Suction Pressures During Iron Ore Sintering', ISIJ International, 62 1768-1776 (2022) [C1]
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Nova |
2022 |
Nguyen TBT, Mitra S, Evans GM, Doostmohammadi H, Monaghan BJ, Zulli P, et al., 'Segregation of a Phosphorus Rich Phase During Differential Solidification of BOF Slag', Metallurgical and Materials Transactions B, 53 3054-3070 (2022) [C1]
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Nova |
2021 |
Singh T, Li H, Zhang G, Mitra S, Evans G, O'Dea D, Honeyands T, 'Iron ore sintering in milli-pot: Comparison to pilot scale and identification of maximum resistance to air flow', ISIJ International, 61 1469-1478 (2021)
In the iron ore sintering process, the resistance to air flow is a major factor in deciding the flame front speed, which influences the sinter productivity and quality. In this wo... [more]
In the iron ore sintering process, the resistance to air flow is a major factor in deciding the flame front speed, which influences the sinter productivity and quality. In this work, pressure drop during sintering and the resistance to air flow was investigated in milli-pot sintering for different coke rates. The sintering experiments were conducted in a milli-pot (diameter 53 mm, height 400 mm) and pressure and temperature were measured at the same locations in the bed by four taps located equidistant to each other. The yield of sinter product was measured following a modified drop test and the mineralogy of the sinter product was analysed. The results from milli-pot sintering were then compared to the reported results from standard pilot-scale sintering, and it was found that the lower half of the milli-pot bed gave a reasonable representation of the pilot-scale sintering process. The results of sinter mineralogy, yield and productivity of the lower half of milli-pot at 5.5-8.0% coke rate were found to be similar to pilot-scale sintering tests at a corresponding coke rate from 3.5 to 5.5%. The maximum resistance to air flow in the bed was found to be in the region between the leading edge of the flame front at ~100°C and the trailing edge of the flame front at ~1 200°C. This suggests that the maximum resistance to air flow includes the effect of de-humidification and combustion in addition to the high temperature "flame front" region usually defined at temperatures above 1 100°C or 1 200°C.
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2021 |
Nguyen TBT, Mitra S, Evans G, Monaghan B, Zulli P, Jang K-O, et al., 'Determining Drag Coefficient of Simplified Dendritic Particles in Metallurgical Systems', Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, (2021) [C1]
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Nova |
2021 |
Nguyen TBT, Mitra S, Evans G, Monaghan BJ, Zulli P, Jang K-O, et al., 'Numerical Study into Gravity Separation of Phosphorus from BOS Slag during Solidification', ISIJ International, 61 705-714 (2021) [C1]
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Nova |
2021 |
Mitra S, Mainul Hoque M, Evans G, Nguyen AV, 'Direct visualisation of bubble-particle interactions in presence of cavitation bubbles in an ultrasonic flotation cell', Minerals Engineering, 174 (2021) [C1]
In this study, the role of cavitation bubbles in the bubble-particle interaction dynamics was investigated using high-speed imaging. A lab-scale conceptual flotation cell was desi... [more]
In this study, the role of cavitation bubbles in the bubble-particle interaction dynamics was investigated using high-speed imaging. A lab-scale conceptual flotation cell was designed involving an ultrasonic field with adjustable power output and a continuous liquid recirculation stream. Coarse size range hydrophobic glass Ballotini particles were suspended in the cell by the combined action of a confined vortex and turbulence created by periodic ultrasonic pulses. Ultrasonic pulses in the liquid medium led to the generation of numerous fine size range cavitation bubbles which were observed to form particle clusters. These particle clusters were observed attaching to relatively larger size carrier bubbles forming stable bubble-particles aggregates, which subsequently floated. It was noted that a favourable state of bubble-particle interactions was achievable to produce such stable bubble-particles aggregates by suitably controlling the input power and period of the applied ultrasonic pulse.
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Nova |
2021 |
Singh T, Li H, Zhang G, Mitra S, Evans G, O'Dea D, Honeyands T, 'Iron ore sintering in milli-pot: Comparison to pilot scale and identification of maximum resistance to air flow', ISIJ International, 61 1469-1478 (2021) [C1]
In the iron ore sintering process, the resistance to air flow is a major factor in deciding the flame front speed, which influences the sinter productivity and quality. In this wo... [more]
In the iron ore sintering process, the resistance to air flow is a major factor in deciding the flame front speed, which influences the sinter productivity and quality. In this work, pressure drop during sintering and the resistance to air flow was investigated in milli-pot sintering for different coke rates. The sintering experiments were conducted in a milli-pot (diameter 53 mm, height 400 mm) and pressure and temperature were measured at the same locations in the bed by four taps located equidistant to each other. The yield of sinter product was measured following a modified drop test and the mineralogy of the sinter product was analysed. The results from milli-pot sintering were then compared to the reported results from standard pilot-scale sintering, and it was found that the lower half of the milli-pot bed gave a reasonable representation of the pilot-scale sintering process. The results of sinter mineralogy, yield and productivity of the lower half of milli-pot at 5.5-8.0% coke rate were found to be similar to pilot-scale sintering tests at a corresponding coke rate from 3.5 to 5.5%. The maximum resistance to air flow in the bed was found to be in the region between the leading edge of the flame front at ~100°C and the trailing edge of the flame front at ~1 200°C. This suggests that the maximum resistance to air flow includes the effect of de-humidification and combustion in addition to the high temperature "flame front" region usually defined at temperatures above 1 100°C or 1 200°C.
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Nova |
2021 |
Wang A, Hoque MM, Moreno-Atanasio R, Doroodchi E, Evans G, Mitra S, 'Effect of bubble surface loading on bubble rise velocity', Minerals Engineering, 174 (2021) [C1]
In this study, we report the rising behaviour of the millimetric size ellipsoidal shaped particle-laden bubbles (particle diameter dP ~ 114 µm, bubble diameter dB ~ 2.76 and 3.34 ... [more]
In this study, we report the rising behaviour of the millimetric size ellipsoidal shaped particle-laden bubbles (particle diameter dP ~ 114 µm, bubble diameter dB ~ 2.76 and 3.34 mm) in the range of bubble surface loading (BSL) from 0 to 0.6 both in absence and presence of a surfactant (Sodium Dodecyl Sulphate, 20% CMC). High-speed imaging was used to capture the trajectory of the particle-laden bubble and an image processing methodology was developed to quantify the bubble surface loading. Three different regimes were observed - bubble shape transition (nearly spherical to ellipsoidal), particle detachment (at bubble rear end), and steady (for high BSL) or expansion (for low BSL) of the particle surface covered zone. A threshold for bubble surface loading (BSL ~ 0.40) was determined which had reasonable agreement with the experimental observations. Bubble rise velocity was observed to decrease with bubble surface loading but this trend was less steep in presence of surfactant. It was noted that loss of bubble surface mobility was higher in presence of surfactant, however in absence of surfactant, bubble surface loading contributed significantly to surface immobility. Finally, a correction factor to Schiller-Naumann drag coefficient model was proposed accounting for the bubble surface loading both in presence and absence of surfactant.
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Nova |
2021 |
Hoque MM, Doostmohammadi H, Mitra S, O dea D, Liu X, Honeyands T, 'High Temperature Softening and Melting Interactions Between Newman Blend Lump and Sinter', ISIJ International, 61 2944-2952 (2021) [C1]
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Nova |
2020 |
Khan MS, Evans GM, Nguyen AV, Mitra S, 'Analysis of particle dispersion coefficient in solid-liquid fluidised beds', Powder Technology, 365 60-73 (2020) [C1]
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Nova |
2020 |
Khan S, Karim I, Evans GM, Doroodchi E, Joshi JB, Mitra S, 'Estimation of dispersion coefficient in a solid-liquid fluidised bed system', Powder Technology, 374 560-576 (2020) [C1]
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Nova |
2020 |
Mitra S, Liu X, Honeyands T, Evans G, O'Dea D, Zulli P, 'Pressure-drop Modelling in the Softening and Melting Test for Ferrous Burden', Iron and Steel Institute of Japan (ISIJ) International, 60 1416-1426 (2020) [C1]
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Nova |
2020 |
Wang A, Hoque MM, Moreno-Atanasio R, Evans G, Mitra S, 'Development of a flotation recovery model with CFD predicted collision efficiency', Minerals Engineering, 159 (2020) [C1]
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Nova |
2019 |
Liu XL, Honeyands T, O dea D, Mitra S, Chen J, Qiu GJ, 'Interaction between sinter and lump during softening and melting process', Kang T'ieh/Iron and Steel, 54 19-26 (2019) [C1]
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Nova |
2019 |
Yasmin D, Mitra S, Evans G, 'Analysis of dynamic interactions in a bubble-particle system in presence of an acoustic field', Minerals Engineering, 131 111-123 (2019) [C1]
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Nova |
2018 |
Wang G, Ge L, Mitra S, Evans G, Joshi JB, Chen S, 'A review of CFD modelling studies on the flotation process', Minerals Engineering, 127 153-177 (2018) [C1]
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Nova |
2018 |
Nguyen TTB, Mitra S, Sathe MJ, Pareek V, Joshi JB, Evans GM, Mitra SSK, 'Evaporation of a suspended binary mixture droplet in a heated flowing gas stream', EXPERIMENTAL THERMAL AND FLUID SCIENCE, 91 329-344 (2018) [C1]
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Nova |
2018 |
Liu X, Honeyands T, Mitra S, Evans G, Godel B, George Acres R, et al., 'A Novel Measurement of Voidage in Coke and Ferrous Layers in Softening and Melting under Load Test Using Synchrotron X-ray and Neutron Computed Tomography', ISIJ INTERNATIONAL, 58 2150-2152 (2018) [C1]
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Nova |
2018 |
Hoque MM, Mitra S, Evans GM, Sathe M, Joshi JB, Mitra SSK, 'Modulation of turbulent flow field in an oscillating grid system owing to single bubble rise', CHEMICAL ENGINEERING SCIENCE, 185 26-49 (2018) [C1]
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Nova |
2018 |
Hoque M, Mitra S, Evans G, Pareek V, Joshi JB, 'Effect of bubble on the pressure spectra of oscillating grid turbulent flow at low Taylor-Reynolds number', Chemical Engineering Science, 190 28-39 (2018) [C1]
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Nova |
2018 |
Mitra SSK, Evans G, 'Dynamic surface wetting and heat transfer in a droplet-particle system of less than unity size ratio', Frontiers in Chemistry, 6 (2018) [C1]
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Nova |
2018 |
Mitra S, Evans GM, Doroodchi E, Pareek V, Joshi JB, 'Interactions in droplet and particle system of near unity size ratio (vol 170, pg 154, 2017)', CHEMICAL ENGINEERING SCIENCE, 192 126-127 (2018)
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2018 |
Nguyen TTB, Mitra S, Pareek V, Joshi JB, Evans GM, 'Evaporation of a sessile binary droplet on a heated spherical particle', Experimental Thermal and Fluid Science, 99 558-571 (2018) [C1]
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Nova |
2017 |
Gao Y, Mitra S, Wanless EJ, Moreno-Atanasio R, Evans GM, 'Interaction of a spherical particle with a neutrally buoyant immiscible droplet in salt solution', Chemical Engineering Science, 172 182-198 (2017) [C1]
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Nova |
2017 |
Ghatage SV, Khan MS, Peng Z, Doroodchi E, Moghtaderi B, Padhiyar N, et al., 'Settling/rising of a foreign particle in solid-liquid fluidized beds: Application of dynamic mesh technique', CHEMICAL ENGINEERING SCIENCE, 170 139-153 (2017) [C1]
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Nova |
2017 |
Mitra SSK, 'Letter to the Editor: Comment on "Evaporation phenomenon past a rotating hydrocarbon droplet of ternary components"', International Journal of Heat and Fluid Flow, 67 278-279 (2017)
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2017 |
Khan MD, Evans GM, Peng Z, Doroodchi E, Moghtaderi B, Joshi JB, et al., 'Expansion behaviour of a binary solid-liquid fluidised bed with different solid mass ratio', ADVANCED POWDER TECHNOLOGY, 28 3111-3129 (2017) [C1]
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Nova |
2017 |
Khan MS, Mitra S, Ghatage S, Doroodchi E, Joshi JB, Evans GM, 'Segregation and dispersion studies in binary solid-liquid fluidised beds: A theoretical and computational study', Powder Technology, 314 400-411 (2017) [C1]
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Nova |
2017 |
Mitra SSK, Evans GM, Doroodchi E, Pareek V, Joshi JB, 'Interactions in droplet and particle system of near unity size ratio', Chemical Engineering Science, 170 154-175 (2017) [C1]
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Nova |
2016 |
Mitra S, Doroodchi E, Evans GM, Pareek V, Joshi JB, 'Interaction Dynamics of a Spherical Particle with a Suspended Liquid Film', AICHE JOURNAL, 62 295-314 (2016) [C1]
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Nova |
2016 |
Mitra S, Thi BTN, Doroodchi E, Pareek V, Joshi JB, Evans GM, 'On wetting characteristics of droplet on a spherical particle in film boiling regime', CHEMICAL ENGINEERING SCIENCE, 149 181-203 (2016) [C1]
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Nova |
2016 |
Wang G, Nguyen AV, Mitra S, Joshi JB, Jameson GJ, Evans GM, 'A review of the mechanisms and models of bubble-particle detachment in froth flotation', Separation and Purification Technology, 170 155-172 (2016) [C1]
Only when the process of particle detachment is well understood and modelled can minerals recovery using the flotation process be modulated to achieve a high efficiency by suitabl... [more]
Only when the process of particle detachment is well understood and modelled can minerals recovery using the flotation process be modulated to achieve a high efficiency by suitably changing the operating parameters. This is vitally necessary for the recovery of coarse particles in an energy efficient way, as detachment is the key limiting factor in the successful recovery of large particles. However, until the detachment mechanism is more fully understood, an upper limit on the floatable particle diameter still remains unidentified. To assess the current state of knowledge available in this area, a comprehensive literature review on the mechanisms and models of the bubble-particle detachment process in froth flotation is presented. In general, the detachment process is considered to be a stochastic process, and is usually attributed to the dynamic interactions with the turbulent flow structures (eddies) in the flotation environment which cause particles to detach because of dissipating energy. In this paper, previous studies on bubble-particle detachment have been critically analyzed with respect to the formulation of the models in predicting the detachment probability of particles. The models are classified into three different categories: force balance analysis; energy balance analysis and empirical analysis of particle size compared to maximum floatable particle size. Attention is also paid to an understanding of the mechanisms of bubble-particle detachment in quiescent and turbulent liquid flow fields. The predictions of all these models have been compared with the published experimental data and it was found that models which take an accurate consideration of the influence of eddies on a particle's detachment give the closest predictions. The generally held concept of bubble-particle detachment inside an eddy was experimentally validated, where a particle was observed to rotate on the surface of a bubble, resulting in a centrifugal acceleration 20 times that of gravitational acceleration. The aim of this paper is to review the developments and limitations of the existing models. The experimental work is reviewed so as to reveal the mechanisms of bubble-particle detachment. Therefore, the future development of models is identified in order to successfully predict particle detachment.
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Nova |
2016 |
Hoque MM, Mitra S, Sathe MJ, Joshi JB, Evans GM, 'Experimental investigation on modulation of homogeneous and isotropic turbulence in the presence of single particle using time-resolved PIV', Chemical Engineering Science, 153 308-329 (2016) [C1]
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Nova |
2016 |
Nguyen TBT, Mitra S, Duong VD, Nguyen VD, Evans GM, 'The effects of variable thermophysical properties on droplet evaporation in high temperature convective flow environment', Journal of Science and Technology, 6 21-24 (2016) [C1]
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Nova |
2015 |
Gao Y, Wang G, Evans GM, Wanless EJ, Sathe M, Mitra S, Moreno-Atanasio R, 'Modelling the Motion of a Collected Particle over a Bubble Surface', Procedia Engineering: New Paradigm of Particle Science and Technology Proceedings of The 7th World Congress on Particle Technology, 1346-1355 (2015) [C1]
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Nova |
2015 |
Nguyen TTB, Mitra S, Pareek V, Joshi JB, Evans G, 'Comparison of vaporization models for feed droplet in fluid catalytic cracking risers', Chemical Engineering Research and Design, 101 82-97 (2015) [C1]
Vaporization of atomized feedstock is one of the critical processes in fluid catalytic cracking (FCC) risers; which is more often ignored in most of the FCC riser modelling studie... [more]
Vaporization of atomized feedstock is one of the critical processes in fluid catalytic cracking (FCC) risers; which is more often ignored in most of the FCC riser modelling studies. In this study, two different vaporization mechanisms of feedstock namely homogeneous mode and heterogeneous mode were studied. Different homogeneous models duly validated for various pure component droplets were applied to predict the vaporization time of the feed droplets typically expected in FCC feed vaporization zone. A new physical model for heterogeneous vaporization considering droplet-particle collision mechanics was also developed in the present study which compared well with the other existing heterogeneous modelling approaches. Comparison of the two vaporization modes indicates that under typical operating conditions of FCC riser, vaporization time of feed droplets predicted by heterogeneous mode is always lower than the homogeneous mode at least by an order of magnitude due to significant increase in heat transfer coefficient which accounts for droplet-particle contact. It is expected that actual vaporization time of feed droplets in an industrial FCC riser should lie in the range predicted by these two vaporization mechanisms which actually set the two limiting modes of vaporization. Obtained results predicted by the models could be used to aid design of the FCC feed vaporization zone.
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Nova |
2015 |
Wang G, Gao Y, Mitra S, Li Y, Zhou S, Evans G, 'Instantaneous bond number for a particle detaching from a bubble', International Journal of Mineral Processing, 142 22-29 (2015) [C1]
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Nova |
2015 |
Hoque MM, Sathe MJ, Mitra S, Joshi JB, Evans GM, 'Comparison of specific energy dissipation rate calculation methodologies utilising 2D PIV velocity measurement', Chemical Engineering Science, 137 752-767 (2015) [C1]
It is critical to have an efficient energy budget in all the industrial process applications involving multiphase flow system where a significant amount of power is invested to ac... [more]
It is critical to have an efficient energy budget in all the industrial process applications involving multiphase flow system where a significant amount of power is invested to achieve a desired outcome such as valuable particle collection and recovery in mineral flotation circuits. In order to achieve this aim there needs to be an ability to properly characterise the energy dissipation in the system; and from this knowledge to develop methodologies so that the supplied energy is distributed suitably among the eddies of different sizes which are responsible for enhancing different transport events such heat/mass transfer, mixing etc. The aim of the study was to obtain the 2D instantaneous velocity field in a homogeneous near isotropic turbulence field using particle image velocimetry (PIV) and then compute the space and time averaged specific energy dissipation rate from velocity field using four different methods, namely: (1) dimensional analysis, (2) velocity gradient, (3) structure function, and (4) energy spectrum. The system was studied in the Taylor Reynolds number range of 24-60, where it was found that the difference between the computed specific energy dissipation rates could be as much as 100 percent. Whilst it was found that there were uncertainties in all four methodologies, it is argued that the energy spectrum method is likely to give the most realistic quantification of the specific energy dissipation rate value since it was shown to satisfy the system energy balance which was not possible to do so for the other three methods. The energy spectrum method also had the added benefit of incorporating integral scale, Taylor microscale and Kolmogorov length scales in the quantification of the specific energy dissipation rate; whereas the other three methods are limited to either integral scale or Taylor microscale only. The limitation of the energy spectrum method, however, is the resolution of the energy spectrum down to the Kolmogorov length scale due to the noise in the measurement; and to resolve this problem a filter was applied to denoise in the dissipation range.
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Nova |
2015 |
Mitra S, Doroodchi E, Pareek V, Joshi JB, Evans GM, 'Collision behaviour of a smaller particle into a larger stationary droplet', ADVANCED POWDER TECHNOLOGY, 26 280-295 (2015) [C1]
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Nova |
2015 |
Gumulya M, Utikar RP, Pareek V, Mead-Hunter R, Mitra S, Evans GM, 'Evaporation of a droplet on a heated spherical particle', CHEMICAL ENGINEERING JOURNAL, 278 309-319 (2015) [C1]
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Nova |
2014 |
Wang G, Sathe M, Mitra S, Jameson GJ, Evans GM, 'Detachment of a bubble anchored to a vertical cylindrical surface in quiescent liquid and grid generated turbulence', Canadian Journal of Chemical Engineering, 92 2067-2077 (2014) [C1]
Turbulence plays a critical role in detachment process of bubble from a solid surface. To investigate this effect, detachment process of a stationary air bubble from a nozzle in b... [more]
Turbulence plays a critical role in detachment process of bubble from a solid surface. To investigate this effect, detachment process of a stationary air bubble from a nozzle in both quiescent and turbulent liquid field was studied. A stationary vertical (flat-ended) needle of ID 1.24mm was used as a nozzle to generate a bubble which was anchored to the needle tip. Different sizes of bubbles were generated in quiescent liquid. Volume and contact angle for these bubbles were measured precisely using microscopic imaging technique and correlated. In the quiescent case experiments, a constant contact angle of 90° and bubble diameter of 3.05±0.004mm were obtained consistently. A simple force balance approach was proposed assuming bubble in equilibrium to determine this maximum bubble diameter during detachment. The detached bubble size calculated using this approach agreed fairly well with the experimental results. An oscillating grid device capable of operating at different frequencies was then applied to generate a homogeneous, near-isotropic turbulent velocity field around the anchored bubble. It was observed that for detachment of smaller bubbles, higher turbulence intensity was indeed necessary. The turbulent flow field was quantified using particle image velocimetry (PIV) technique and resolved into flow structures (eddies) of different length scales using a Gaussian filter. It was concluded that smaller eddies perturbed the bubble interface whilst the larger eddies contributed to weakening of the capillary force causing the bubble detachment. Energy dissipation profile obtained from the PIV images indicated significant energy dissipation near the bubble compared to the bulk fluid which supported the fact that strong interactions between bubble and eddies were indeed responsible for bubble detachment.
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2014 |
Gumulya M, Utikar RP, Pareek V, Tade MO, Mitra S, Evans GM, 'Modelling of the interaction between a falling n-heptane droplet and hot solid surface', Chemical Engineering Science, 116 23-37 (2014) [C1]
Accurate prediction of the interactions between evaporating liquid droplets and solids are critical for many industrially important processes. A model based on coupled Level Set-V... [more]
Accurate prediction of the interactions between evaporating liquid droplets and solids are critical for many industrially important processes. A model based on coupled Level Set-Volume of Fluid approach was developed to simulate the interaction of evaporating liquid droplets with hot solid surfaces. The model incorporates appropriate source terms in the multiphase calculations to account for the heat and mass transfer. Accurate and stable numerical procedure was developed and incorporated in open source solver OpenFOAM. A brief discussion on the model development along with several key issues that are associated with this process was presented. The resulting numerical model was validated through the experimental data of Chandra and Avedisian (Chandra, S., Avedisian, C.T., 1991. Proc. R. Soc. Lond., Ser. A 432, 13-41). Although some discrepancies were found between the numerical results and experimental data, the model was found to be capable of reproducing the reduced droplet spreading rate as the temperature of the surface is increased away from the saturation temperature. The decrease in rate of surface wetting results from the combined effects of surface tension, viscous forces and evaporation at the liquid-solid-vapour contact line. Further, the effects of increased pressure at the solid-liquid interface resulting from the rapid evaporation of the liquid, which in some cases can be quite severe such that the liquid gets lifted-off from the surface, were also captured, in good agreement with experimental observations. Finally, the effects of the solid temperature on the evaporation and heat transfer rates of the droplets were presented and analysed. © 2014 Elsevier Ltd.
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Nova |
2013 |
Mitra S, Sathe MJ, Doroodchi E, Utikar R, Shah MK, Pareek V, et al., 'Droplet impact dynamics on a spherical particle', CHEMICAL ENGINEERING SCIENCE, 100 105-119 (2013) [C1]
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2012 |
Mitra SS, 'Control moisture problems in slurry-based polyolefin operations', Hydrocarbon Processing, 91 77-82 (2012) [C1] |
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Nova |