•Ionic liquid-based membrane contactor setup for CO2 capture was modeled.•Isothermal model predicted high temperature pre-combustion CO2 capture operation.•Comparative analysis was performed for ...different number of membrane fibers.•CO2 flux, mass transfer coefficients and separation efficiencies were investigated.•Transient state of CO2 absorption was studied against different operating parameters.
A pre-combustion carbon capture process at high temperatures in membrane contactor setup using ionic liquid 1-Butyl-3-methlyimidazolium tricyanomethanide (BmimTCM) as an absorbent was studied here by developing a comprehensive mathematical model. A detailed 2D mass transport model based on finite element analysis was presented for this purpose. The model considers molecular diffusion in both axially and radially. The effects of various operational parameters were studied for CO2 absorption flux. A comparative study was carried out among different membrane contactor modules having different number of fibers. The increase in number of fibers has significantly enhanced the CO2 absorption process. An increase of 31% in the CO2 separation efficiency was observed by increasing the number of fibers from 1 to 10. Furthermore, the transient state behavior of CO2 concentration during the absorption process until reaching a steady state was systematically studied for various operating temperatures and gas flow rates.
Interfacial pH changes and bubble dynamics play pivotal roles in water electrolysis, significantly impacting cell overvoltage and energy consumption. The quantification of these changes has proven ...challenging, given the traditional focus on bulk solution pH fluctuations. In contrast to previous studies on individual bubble growth, this research adopts a distinctive approach, analyzing over than 8,000 bubbles in each experiment through advanced image processing computational procedures for edge detection. This methodology provides extensive data for comprehensive statistical analysis. Furthermore, the study delves into the generation of H2 and O2 bubbles during water electrolysis in both acidic and alkaline media, employing a platinum strip electrode. Crucial experimental variables, such as electrolyte pH, gas type, and current density, are systematically explored for their influence on bubble size and distribution using a 23 factorial design. In addition to this work, finite element simulations were conducted to model interfacial pH under the same experimental conditions. These simulations substantiate our experimental findings, confirming the occurrence of interfacial pH transitions in some instances. This transition, in turn, influences the bubble size distribution and consequently impacts cell voltage. These experimental and simulated datasets and potential curves allow for comparing interfacial pH changes with bubble size and the cell voltage relationship. With broad implications for various applications, such as energy production and material development, where interfacial pH changes and bubble formation are essential, this novel approach allows the optimization of boundary conditions for more effective electrochemical processes.
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•Experimental and simulation data show interfacial pH impact on water electrolysis.•Interfacial pH changes affect bubble size distribution and cell potential in water electrolysis.•The pH variation’s impact on electrochemical processes can guide system optimization.
•Application of coarse grain DEM model to 3D polydisperse cold flow model.•Validation is carried out with experimental capacitance in-situ probe measurements.•Simulated solid velocities and ...concentrations are in good agreement with measurements.•Homogenous drag model was not capable to qualitatively predict solid distribution as EMMS.
A cold flow circulating fluidized bed (CFB) reactor is simulated under three fluidization velocities with the coarse grain discrete element method (DEM) using two different polydisperse particle systems namely glass beads and slightly coarser sand particles of Geldart A-B range. Particle velocities and particle concentration were measured by capacitance probe for the validation of the numerical model. The simulations were carried out using a homogenous drag model and a structure dependent drag model using the theory of energy minimization multiscale method (EMMS). Numerical parameters like grid resolution and computational time were investigated for the coarse grain CFD-DEM model, suggesting a cell uniformity criteria that might lead to more mesh independent results. The simulated macroscopic quantities such as pressure profile are generally in good agreement for all simulated cases using the EMMS model. Microscopic quantities such as particles velocities and solids concentration are partially matched well with the experimental data. The qualitative profiles of particle velocity and particle concentration are in better agreement for the EMMS model than for the homogenous drag model. The simulated reactor outflux using glass beads is well matched with experiment. The simulated reactor outflux with sand material is overestimated with EMMS model, although not that strong as for the Gidaspow model, in comparison to experimental measurements. One reason for the discrepancy is due to the cluster diameter correlation that require further development to be applicable in turbulent fluidization flow regime. Further model improvements are discussed and solutions are provided.
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•3-D micro-scale model of the fibrous filter was reconstructed using Python codes.•CFD-DPM model was established to simulate filtration performance of fibrous media.•RSM was utilized ...to investigate the relationship between performances and parameters.•The CFD simulation coupled RSM was adopted to realize multi-objective optimization.
Fibrous-filtration media has been demonstrated with the ability to separate particulate matter in the gas. However, the complexity of involved parameters and the intricate interior structure of fibrous media pose great challenges for filter design and optimization. Herein, a novel numerical method was proposed to predict and optimize the fibrous-filtration progress by employing the computational fluid dynamic (CFD) simulation coupled with the response surface methodology (RSM). The involved filtration parameters exerted synergetic effects on filtration efficiency, which can be explained by the coupling effect of basic filtration principles with the variation of the Stk number and Pe number. Meanwhile, the pressure drop increased with the elevated solid volume fraction and airflow velocity but was not affected by the variation of particle diameters. This combined methodology of CFD simulation with RSM optimization paved a new path for the high-efficient screening of the filter design and optimization.
Rapid prediction of the removal efficiency and energy consumption of organic contaminants under various operating conditions is crucial for advanced oxidation processes (AOPs) in industrial ...application. In this study, 1H-Benzotriazole (BTZ, CAS: 95-14-7) is selected as a model micropollutant, a validated incorporated Computational Fluid Dynamics (CFD) model is employed to comprehensively investigate the impacts of initial concentrations of H2O2, BTZ and dissolved organic carbon (DOC) (i.e., DOC0, BTZ0 and DOC0), as well as the effective UV lamp power P and volumetric flow rate Qv. Generally, the operation performance depends on DOC0 and BTZ0 in similar trends, but with quantitatively different ways. The increase in H2O20 and P/Qv can promote •OH generation, leading to the elimination of BTZ. It is worth noting that P/Qv is found to be linearly correlated with the removal order of BTZ (ROBTZ) under specific conditions. Based on this finding, the degradation of other potential organic contaminants with a wide range of rate constants by UV/H2O2 is further investigated. A model for predicting energy consumption for target removal rates of organic pollutants is established from massive simulation data for the first time. Additionally, a handy Matlab app is first developed for convenient application in water treatment. This work proposes a new operable solution for fast predicting operation performance and energy consumption for the removal of organic contaminants in industrial applications of advanced oxidation processes.
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•The photochemical degradation process of BTZ was simulated using an CFD model.•The performance of the system depends on P, Qv, H2O20, DOC0 and BTZ0.•A linear relationship between P/Qv and ROBTZ was proposed for the first time.•The predicted P/Qv at target RBTZ of 60–99 % were obtained with various conditions.•An App was developed for estimating the energy consumption in industrial practice for the first time.
This work shows the analysis of ethanol steam reforming process within a catalytic membrane reactor. A 2-D non-isothermal CFD model was developed using Comsol Multiphysics, based on previous ...experimentally validated isothermal model. A comprehensive heat and mass transfer study was carried out utilizing the model. Operating conditions such as liquid hourly space velocity (LHSV) (3.77–37.7 h−1), temperature (673–823 K), reaction side pressure (4–10 bar) and permeate side sweep gas flow pattern were discussed. A temperature gradient along the reactor was observed from the model and a “cold spot” was seen at the reactor entrance area, which is unfavorable for the highly endothermic ethanol steam reforming process. By changing the sweep gas pattern to counter-current, the “cold spot” appears to be smaller with a reduced temperature drop. By studying the individual reaction rates, reverse methane steam reforming (methanation) was observed, caused by the low temperature in the “cold spot”. Optimal operating conditions were found to be under LHSV = 37.7 h−1 and counter-current sweep gas conditions.
•Non-isothermal CFD model for ethanol steam reforming process is developed.•Temperature gradient and a “cold spot” is observed in the reactor.•Reactor is used more efficiently under counter-current sweep gas operation.•Counter-current sweep gas lowers the “cold spot”, benefits endothermic reactions.•Higher temperature and pressure are found to be beneficial for hydrogen production.
•The Gaussian process regression(GPR) model is used to fit the experimental data.•The agreement between an experiment and the simulation is replaced by comparing outputs of the simulation and the GPR ...model.•Two metrics are used to provide tangible information for the local and global agreement, repectively.•The quantitative information helps to make an objective argument for the accuracy level of a CFD model.
This paper presents a Gaussian process regression inspired method to measure the agreement between experiment and computational fluid dynamics (CFD) simulation. Because of misalignments between experimental and numerical outputs in spatial or parameter space, experimental data are not always suitable for quantitative assessing the numerical models. In this proposed method, the cross-validated Gaussian process regression (GPR) model, trained based on experimental measurements, is used to mimic the measurements at positions where there are no experimental data. The agreement between an experiment and the simulation is mimicked by the agreement between the simulation and GPR models. The statistically weighted square error is used to provide tangible information for the local agreement. The standardised Euclidean distance is used for assessing the overall agreement.
The method is then used to assess the performance of four scale-resolving CFD methods, such as URANS k-ω-SST, SAS-SST, SAS-KE, and IDDES-SST, in simulating a prism bluff-body flow. The local statistically weighted square error together with standardised Euclidean distance provide additional insight, over and above the qualitative graphical comparisons. In this example scenario, the SAS-SST model marginally outperformed the IDDES-SST and better than the other two other, according to the distance to the validated GPR models.
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•A novel distributor obtains better liquid distribution without pump pressure.•A CFD simulation was accurately validated by high-speed camera imaging.•The flow behavior of liquid jet ...impacting on the liquid distributor was studied.•The impacting angle between the liquid and the wire mesh packing was obtained.
Rotating packed beds (RPBs) have been widely applied in multiphase systems. When handling some extreme operating condition systems, finding a suitable pump to provide pressure to force the feeding liquid to be evenly distributed by the distributor of the RPB is very costly. In this work, we designed new liquid distributors by using the kinetic energy of the rotating shaft as driving force to obtain uniform distribution. The performance of the liquid distribution has been investigated in terms of liquid flow behavior, liquid velocity, and impacting angle (α). Compared with bar and cantboard distributors, the radlamelle liquid distributor had the best distribution performance. By further optimization of the radlamelle structure, the left-hand wheel had better dispersion performance with α varying from 24.3 to 79.1°. This new liquid distributor without pump pressure expands the applications of the RPB in ultra-low or high temperature and high pressure operating conditions.
To determine the safe boundary of fuel assembly operation and improve the heat transfer performance of fuel assembly, it is necessary to accurately calculate the thermohydraulic characteristics and ...the critical heat flux (CHF) in rod bundles. The Eulerian two-phase model coupled with extended wall boiling model was used to numerically investigate the 5 × 5 fuel rod bundle flows with four sets of mixing vane spacer grids. A wide range of working conditions were analyzed to validate the numerical method. The results indicate that the current numerical model can not only accurately calculate the CHF values but also predict the location of heat transfer crisis. Based on CFD (Computational Fluid Dynamics) results, the detailed two-phase flow distributions were provided to analyze the CHF performance under special structures, such as bowed rod and spacer backward shift. The quantitative results were obtained on the analyses of spacer position influence on CHF and the penalty effect of bowed rod. Furthermore, the prediction of present numerical model under low inlet subcooling conditions and cold rod CHF were discussed. The research of this paper provides support for the design and optimization of fuel assemblies.
