CFD modelling of conjugate heat transfer in a pilot‐scale unbaffled stirred tank reactor with a plain jacket

Bentham, Erik James; Heggs, Peter J.; Mahmud, Tariq

doi:10.1002/cjce.23360

Cited by 10 publications

(9 citation statements)

References 25 publications

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“…Nevertheless, at larger scales, such as industrial scales, this could be a problem because of difficulties in mixing and temperature regulation. 31,34 This will be discussed further in Section 4.3.…”

Section: Resultsmentioning

confidence: 99%

Isothermal by Design: An Accelerated Approach to the Prediction of the Crystallizability of Slowly Nucleating Systems

Kaskiewicz

Lai

et al. 2019

Org. Process Res. Dev.

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A route to the accelerated nucleation of α-para-aminobenzoic acid in ethanol/water (EtOH/H2O) mixed solvent solutions, using antisolvent crystallization, is presented. An isothermal by design approach is adopted, whereby the exothermic enthalpy of mixing associated with antisolvent addition is offset by the control of the temperature of the antisolvent added. Induction times (τ) are found to be reduced by 4 orders of magnitude using this methodology, consistent with the use of this approach as a nucleation acceleration technique. Calculation of the nucleation kinetic parameters for a range of solution concentrations, compositions, and supersaturations (S) reveal that effective interfacial tensions (γeff) vary from 8.4 to 2.3 mJ m–2 from solutions in H2O solvent and EtOH solvent, respectively, in line with the trend in solubility. The critical nucleus radius (r*) decreases from 1.98 to 0.40 nm associated with a decrease in the number of molecules in the critical nucleus (i*) from 196 to 2 molecules. A change in nucleation mechanism from heterogeneous nucleation to homogeneous nucleation is observed to take place at S ≈ 1.5. Limitations, particularly with focus toward larger-scale operation, are highlighted together with potential solutions to overcome such aspects.

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Section: Resultsmentioning

confidence: 99%

Isothermal by Design: An Accelerated Approach to the Prediction of the Crystallizability of Slowly Nucleating Systems

Kaskiewicz

Lai

et al. 2019

Org. Process Res. Dev.

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“…The study of heat transfers within the stirred reactors is very important since they are crucial in many relevant operations. For example, they are critical to achieve the desired reaction products and prevent the thermal lose control of reactions, as well as to generate the appropriate supersaturation for the product of promising crystals [3].…”

Section: Introductionmentioning

confidence: 99%

“…Early research works mainly involved the simulation of heat transfers in mixers with different configurations such as the rounded-bottom vessel with an atypical helical ribbon impeller [9] and the stirred tanks with improved Intermig impellers [10]. Other researchers have focused on the heat transfer characteristics of different fluids in stirred tanks and in a jacketed stirred heat exchanger [3,[11][12][13][14][15]. Johnson et al [15] derived a non-adiabatic heat-transfer model for the study of heat transfers in laboratory to pilot-scale reactors, which could be used to predict the temperature distribution within the uncertainty of the experimental measurements.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer and Hydrodynamics in Stirred Tanks with Liquid-Solid Flow Studied by CFD–DEM Method

Luo

Wang

et al. 2021

Processes

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The heat transfer and hydrodynamics of particle flows in stirred tanks are investigated numerically in this paper by using a coupled CFD–DEM method combined with a standard k-e turbulence model. Particle–fluid and particle–particle interactions, and heat transfer processes are considered in this model. The numerical method is validated by comparing the calculated results of our model to experimental results of the thermal convection of gas-particle flows in a fluidized bed published in the literature. This coupling model of computational fluid dynamics and discrete element (CFD–DEM) method, which could calculate the particle behaviors and individual particle temperature clearly, has been applied for the first time to the study of liquid-solid flows in stirred tanks with convective heat transfers. This paper reports the effect of particles on the temperature field in stirred tanks. The effects on the multiphase flow convective heat transfer of stirred tanks without and with baffles as well as various heights from the bottom are investigated. Temperature range of the multiphase flow is from 340K to 350K. The height of the blade is varied from about one-sixth to one-third of the overall height of the stirred tank. The numerical results show that decreasing the blade height and equipping baffles could enhance the heat transfer of the stirred tank. The calculated temperature field that takes into account the effects of particles are more instructive for the actual processes involving solid phases. This paper provides an effective method and is helpful for readers who have interests in the multiphase flows involving heat transfers in complex systems.

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“…One of the primary features of unbaffled and partially baffled agitated vessels is the highly swirling liquid motion, which leads to the formation of a central vortex causing a depression in the liquid free surface. For an improved accuracy of CFD predictions, it is important to model the shape of the liquid free surface because it affects the flow field, , as well as the area of heat transfer to the ullage region and at the vessel wall . Despite a widespread use of vessels with a single baffle agitated by a RCI in the pharmaceutical as well as in the fine chemicals industries, a limited body of work on their hydrodynamic and mixing performance has been reported; even basic information such as vortex depth, power, and flow number correlations are rarely found in the open literature.…”

Section: Introductionmentioning

confidence: 99%

Digital Design of Batch Cooling Crystallization Processes: Computational Fluid Dynamics Methodology for Modeling Free-Surface Hydrodynamics in Agitated Crystallizers

Corzo

Yue

Mahmud

2020

Org. Process Res. Dev.

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A framework for the digital design of batch cooling crystallization processes is presented comprising three stages, which are based on different levels of process complexity, integrating crystallizer hydrodynamics with crystallization kinetics and consequently with expected crystal size distribution. In the first stage of the framework, a computational fluid dynamics methodology is developed to accurately assess hydrodynamics in a typical batch crystallizer configuration, comprising a 20 L scale dish-bottom vessel with a single beavertail baffle agitated by a retreat curve impeller, used in the pharmaceutical as well as in the fine chemical industries. The hydrodynamics of crystallizers with such configurations is characterized by vortex formation on the free liquid surface. It is therefore important to model the free surface using the Volume-of-Fluid (VoF) method. Comparison of the predicted mean velocity components with experimental measurements using laser Doppler anemometry reveals that improved predictions are obtained using a differential Reynolds-stress transport model for turbulence coupled with the VoF for modeling the gas-liquid interface compared with those using the Shear-stress transport model and with a flat liquid surface. This study demonstrates that an accurate treatment of the liquid free surface for capturing vortex formation is essential for reliable predictions of the crystallizer's flow field. While the vortex depth is predicted to increase with increasing impeller Reynolds number, the dependence of hydrodynamic macroparameters, including power number, impeller flow number, and secondary circulation flow number, on Reynolds number reveals that they are essentially constant within the turbulent regime but fluctuate when the flow is in the transitional and laminar regimes as fluid viscosity increases.

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CFD modelling of conjugate heat transfer in a pilot‐scale unbaffled stirred tank reactor with a plain jacket

Cited by 10 publications

References 25 publications

Isothermal by Design: An Accelerated Approach to the Prediction of the Crystallizability of Slowly Nucleating Systems

Isothermal by Design: An Accelerated Approach to the Prediction of the Crystallizability of Slowly Nucleating Systems

Heat Transfer and Hydrodynamics in Stirred Tanks with Liquid-Solid Flow Studied by CFD–DEM Method

Digital Design of Batch Cooling Crystallization Processes: Computational Fluid Dynamics Methodology for Modeling Free-Surface Hydrodynamics in Agitated Crystallizers

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