Simulation Of Mass Transfer Research Articles

Preliminary study of oxygen mass transfer in the primary circuit of lead cooled fast reactor

This paper describes the development of a novel multi-scale and physics-chemical coupling system KMC-SUBTra-MC/TrioCFD based on the ICoCo interface and its application in a Lead-cooled Fast Reactor (LFR) named M2LFR-1000. This system is developed to integer a novel Thermal-Hydraulic code KMC-SUBtra-MC which is capable to simulate the oxygen/corrosion product mass transfer and oxidation/corrosion behaviour of the reactor core, and a Computational Fluid Dynamic (CFD) code TrioCFD for Primary circuit except the core, enabling the solution to produce more realistic mass transfer simulation within the LFR. With the novel coupling system, a first preliminary understanding of the distribution of oxygen concentration in LFR can be obtained. The results show that when there is no pre-oxidized film on the surface of the fuel cladding, the system will face the risk of increased corrosion in the early stage of operation. An optimization method is proposed, which will be conducive to the operation of the oxygen control system.

Numerical simulation of hydrogen bubble growth and mass transfer on horizontal microelectrode surface under electrode-normal magnetic field

Based on our previous visual experiments and the volume of fluid (VOF) multiphase model, the growth and detachment characteristics of a single hydrogen bubble on the horizontal microelectrode surface under the electrode-normal magnetic field have been numerically investigated. The mass transfer contributions of supersaturated dissolved hydrogen to the bubble growth from the liquid microlayer under the direct injection model and from the bulk bubble interface under the gas–liquid diffusion-controlled model are adopted. The bubble shapes and diameters predicted from the numerical investigation agree well with experimental results under the same conditions. The simulated results indicate that the supersaturated dissolved hydrogen concentration and the mass transfer source at the wedge-shaped areas adjacent to the bubble foot are obviously higher than those in the wider bulk bubble interface regions. The mass transfer contribution to the bubble growth from the liquid microlayer beneath the bubble base directly plays a dominant role. The higher current density and corresponding Lorentz force mainly appears in the wedge-shaped areas, while the higher rotational electrolyte flow velocity appear at oblique positions of the bubble equator. The bubble detachment behavior makes the rotational electrolyte flows is significantly more complex.

Simulation of heat transfer, mass transfer and tissue damage in magnetic nanoparticle hyperthermia with blood vessels

Numerical simulation of magnetic nanoparticle hyperthermia for cancer treatment has been investigated in this study. The presented simulation did account for the effects of fluid flow, mass flow, and heat transfer during the MNP hyperthermia. The tumor was assumed to be a porous slab, 30% of which had been necrosed previously, with two capillaries, where magnetic nanoparticles were added into the bloodstream and distributed in the tumor by blood flow through capillaries. Fluid flow, mass transfer by capillaries, and interstitial tissues have been coupled in this study. Furthermore, tumor tissue damage has been calculated using a thermal damage indicator. The goal of this research is to find an optimum injection duration and exposure time in order to maximize hyperthermia treatment effectiveness using the BOBYQA optimization method. At the end of the 1-h time hyperthermia treatment, most of the non-necrotic tissue of the tumor were damaged. Moreover, the fraction of damaged tissue increased to more than 90% in some parts of the tumor. Results of this study indicate that MNP hyperthermia with the proposed setup can effectively damage the tumor in just one session, making it more susceptible to complementary therapies such as radiotherapy or chemotherapy.

Mass-Transfer Simulation of Salicylic Acid on Weakly Polar Hyper-cross-linked Resin XDA-200 with Coadsorption of Sodium Ion.

The mass-transfer process of salicylic acid on hyper-cross-linked resin XDA-200 was experimentally and theoretically studied. Undissociated salicylic acid was found to be the favorable form for salicylic acid adsorption on the resin. A pH-dependent adsorption isotherm model established in this paper could well fit the adsorption isotherm data at different pH values. Surface diffusion is the main mass-transfer mode for salicylic acid in resin particles. The salicylate anions and Na+ coadsorbed on the resin. The modified surface diffusion model considering the coadsorption was proposed. The model could satisfactorily fit the concentration decay curves of salicylic acid at different pH values and feed concentrations. NaOH aqueous solution at pH 12 could elute salicylic acid in the fixed bed efficiently. A pH-dependent dynamic adsorption and elution process model considering axial diffusion, external mass transfer, surface diffusion, pH-dependent adsorption equilibrium, as well as coadsorption of salicylate anions and Na+ was established. The model could well predict the breakthrough and elution curves at different feed concentrations. The research carried out in this paper has reference significance for optimizing the separation process of salicylic acid and its analogues.

CFD simulation of mass transfer in bubble columns: Detailed study of mass transfer models

The accuracy of the computational fluid dynamics simulations of mass transfer process in bubble columns is significantly influenced by the mass transfer models. Various mass transfer models have been developed based on different theories. However, it is still confusing on the choice of mass transfer models when performing the simulations of mass transfer in bubble columns. In the present work, the applicability and accuracy of three types of widely-used mass transfer models, including the single bubble-based models, the slip velocity model, and the surface renewal stretch model, were assessed with the spatially resolved data of gas holdup and species concentration in the literature. By comparing simulation results with experimental data, the present work provided suggestions on choosing a proper mass transfer model when performing simulations of the mass transfer process in bubble columns. The influence of bubble-induced turbulence and its different modeling approaches on different mass transfer models were investigated.

Interface-resolved direct numerical simulations of interphase momentum, heat, and mass transfer in supercritical water gasification of coal

Interactions between a reacting particle and the surrounding fluid are complex due to the interplay between flow dynamics, heat and mass transfer, and chemical reactions. In the present work, particle–fluid transport processes in supercritical water gasification of coal are studied using high-fidelity interface-resolved direct numerical simulations. The impact of different factors on the particle–fluid interactions are evaluated by performing simulations of the flow around two-dimensional particles considering different numerical configurations. The outgoing Stefan flow from the particle surface is found to cause expanded boundary layers for velocity, heat, and species. The temperature-induced changes in transport properties around a heated particle lead to a higher drag force and decreased heat/mass transport; those differences are further enlarged when taking into account the volumetric expansion of the fluid. Transport limitation for coal gasification in a realistic configuration is finally investigated. Temperature-induced fluid dilatation is then the major factor affecting drag force and heat transfer around the reacting particle, and mass transport is significantly impacted by species production or consumption in the boundary layer. Reaction heat release and variations in fluid composition within the thermal boundary layer lead to a slight enhancement of heat transfer. This work reveals and quantifies the main mechanisms affecting the exchanges between a reacting coal particle and surrounding supercritical water regarding both thermal and chemical aspects. It also provides high-fidelity data to later fit the reduced models needed for simulations of large-scale supercritical water gasification installations.

Numerical simulation and experimental validation of Ti0.95Zr0.05Mn0.9Cr0.9V0.2 alloy in a metal hydride tank for high-density hydrogen storage

In order to achieve rapid hydrogen charging and discharging of high-density hydrogen storage alloys in metal hydride (MH) tank, it is key to optimize the design of MH tank by simulation based on a credible numerical model. Herein, a multi-physical field mathematical model coupled with kinetic equations and heat & mass transfer equations for the de-/hydrogenation of Ti0.95Zr0.05Mn0.9Cr0.9V0.2 alloy in MH tank is proposed. According to experimental kinetic curves, appropriate kinetic equations dominated by different rate control steps are chosen for simulating gas-solid reactions. With excellent match between experimental and simulated kinetic results under different pressure and temperature operating conditions, a novel numerical model is established to predict the local temperature variation during the de-/hydrogenation of Ti0.95Zr0.05Mn0.9Cr0.9V0.2 alloy in a self-designed hydrogen storage tank with high-density hydrogen storage of 55.1 g H2/L. Interestingly, further calculated results reveal that the temperature evolution can be accurately matched, which proves the reliability of the designed numerical model and favors to predict the de-/hydriding behaviors. This investigation provides an effective means for subsequent structure optimization and energy & mass transfer performance optimization of high-density hydrogen storage devices, and sheds light on the numerical simulation of heat & mass transfer for advanced energy storage applications.

Direct numerical simulation of gas-liquid mass transfer around a spherical contaminated bubble in the stagnant-cap regime

Direct Numerical Simulations are performed to investigate the gas-liquid mass transfer around a rising spherical bubble contaminated by insoluble surfactants. The surfactant transport on the bubble surface and the Marangoni effect are taken into account when solving the hydrodynamics, resulting in the stagnant-cap condition. A parametric study is carried out to investigate the mass transfer by varying the Reynolds, Marangoni and Schmidt numbers. A thorough analysis of the impact of surfactants on the bubble hydrodynamics is presented through a correlation for the maximum velocity umax* along the interface as a function of the contamination angle θcap. These two parameters are then found to be crucial to quantify the rate of mass transfer around the interface. The latter is analyzed through the Sherwood number, which decreases when the interface is partially immobilized, between the value for a clean bubble and a solid sphere. A local analysis of the mass flux is carried out, which shows that the boundary layer thickens around the immobilized zone of the interface, and that the transfer rate in the mobile zone is also lower than for a clean bubble at same Re, both effects resulting in a decrease of the global Sh. The latter is in particular very sensitive to the local hydrodynamic condition in the front part of the interface, where the flux is locally higher and which can be characterized by the intensity of the maximum surface velocity. Finally, a correlation is proposed to predict the Sherwood number of a contaminated bubble depending on both global (Re, Sc) and local (θcap, umax*) parameters, with a large range of validity (1≤Re≤100, 1≤Sc≤500, 0≤θcap≤π) based on a comparison with previous numerical studies.

Experimental on physical properties of shale gas under low-velocity seepage and stress sensitivity environment

Shale gas reservoirs have complex pore structures, consisting not only of nanopores within and between organic grains but also of microcracks distributed randomly within the matrix. Although free gas and adsorption gas coexist, free gas is stored in pore spaces, and adsorption gas is stored in organic matter and clay minerals. Due to the presence of organic matter and heterogeneity in shale, the gas transfer mechanism is complicated involving multiple scales. Gas flow in shale does not conform to the characteristics of linear seepage at the low-velocity stage given the occurrence and flow state of different gases under different pressures. Meanwhile, very few studies have been performed on the low-velocity seepage characteristics of different gases in shale. Therefore, it is important to present experimental evidence for the low-velocity seepage law of different gases in shale. The present study uses experimental simulations of gas mass transfer at multi-scales to investigate the low-velocity gas flow and stress sensitivity of shale core samples. The results indicate that the shale matrix has a strong adsorption capacity, and that its helium flow capacity is 1.5–2.0 times greater than that of methane without backpressure. With increasing pore pressure, the combined action of gas adsorbed to the cavity and free gas leads to first an increase and then a decrease in the flow capacity of methane. With a low confining pressure, the permeability decreases exponentially. On the other hand, as the net confining pressure increases, the core fracture closes, causing the gas slip effect to increase permeability. The results of the study may provide valuable guidance in understanding gas flow in shale matrix and in the development of gas reservoirs.

Simulation of mass and heat transfer of Quercus leaf particles during hydrothermal extraction

AbstractMass and heat transfer models of Quercus leaf particles during hydrothermal extraction were developed in COMSOL Multiphysics. The main physical properties used in the model were measured. The results showed that the average particle size was 116.7 μm, and after soaking in water for 24 h, the average particle size increased to 127.3 μm. However, the average particle size increased from 116.7 to 132.8 μm after soaking in a 60% (v/v) ethanol solution for 40 min, and decreased to 127.3 μm after 60 min. The Quercus leaf particles have a higher ability to absorb ethanol solution than water. The simulations showed that it took 3.2 s for the ethanol concentration and 0.5 s for the temperature in the particles to tend stably after soaking in a 60% (v/v) ethanol solution at 40°C. From the edge of the particle to the centre, the increasing rates of ethanol concentration and temperature gradually slowed down, while the changing rates of the centre accelerated with the increase in solution concentration and temperature, respectively. When the particles soaked at the lowest concentration, the central concentration first reached stability, and at the lowest temperature, the centre temperature first stabilized.

A pseudopotential lattice Boltzmann model for simulating mass transfer around a rising bubble under real buoyancy effect

A pseudopotential multicomponent lattice Boltzmann (LB) model that can account for the real buoyancy effect is proposed to simulate the mass transfer process around a rising bubble. The density profiles at the equilibrium state are determined based on the hydrostatic condition and the zero diffusion flux condition (the balance of chemical potential). Compared with the LB models using effective buoyancy force, the proposed model has three advantages: (1) avoiding the unrealistic distribution of gas components within the bubble due to the upward effective buoyancy force, (2) removing the undesirable diffusion process due to the application of effective buoyancy force, and (3) considering the effect of the pressure gradient on the change of bubble size. In addition, Henry's law, which can be automatically recovered from the multicomponent LB equation, is re-interpreted from the perspective of the balance of chemical potential. Simulation results showed that the diffusion flux non-uniformly distributes over the surface of a rising bubble. The diffusion zone primarily occurs at the top and the lateral side of a rising bubble, whereas the diffusion transport just below the rising bubble is much less significant than its counterpart above the rising bubble. Various bubble shapes and their corresponding diffusion zones have been obtained. Moreover, the correlation between the Sherwood number and the Peclet number derived from the simulation results is consistent with those from previous numerical results. Thus, the proposed LB model is capable of conducting a quantitative analysis of the mass transfer around a rising bubble.

Simulation of heat and mass transfer in a random packed column operated as a cooling tower using the TUM-WelChem cell model

Uncertainties due to maldistribution in the operation of packed columns are one of the major issues in column design. Thus, thorough knowledge of the liquid distribution and the mass transfer processes within the packed bed is necessary. Models able to predict maldistribution are crucial for avoiding extensive experimental investigations. In the present study, the TUM-WelChem cell model is expanded by the simulation of heat and mass transfer in a packed column operated as a cooling tower. The simulation approach is based on experimental data obtained at the Technical University of Munich using a Ø0.634 m random packed column. Temperature profiles and global outlet values of liquid and gas temperatures along with the humidities are evaluated and discussed for the Hiflow® ring 50–6 polypropylene. The presented study provides insight into the applicability of the heat and mass transfer calculation by validating the simulation results with experimental data.

Extension of the Simulation Model of Bubble Growth during Phase Change Heat Transfer Using Volume of the Fluid Flow Model

Nucleate boiling is used in numerous engineering applications, such as the chemical, manufacturing, thermal, nuclear, and electronic industries. This research paper deals with the numerical analysis of bubble growth using a fluid flow model. This physical phenomenon of bubble growth has not been discussed mechanically and does not throw light on empirical models. We are discussing this phenomenon in another way to get the required results in this paper. Simulation of bubble growth is already published by measuring the volume of fluid flow; the method is known as VOFF tracking method. Lee’s model has already discussed the phase change that occurs due to evaporation and condensation of the fluid. We have used the method in which the equation terms involving energy and mass source caused by phase change are incorporated into the control equations by additional subroutines written in C language. We have mentioned in detail the results of simulating mass transfer caused by phase change and the effect of subcooling on bubble growth. The results thus obtained show that the subcooling effect prevents the growth of bubbles from growing due to the certain amount of bubble caps in the subcooled area. The effect of evaporation of the liquid increases the size of the bubbles in both the subcooled and the superheated zone.

3D simulation of momentum, heat and mass transfer in potato cubes during intermittent microwave-convective hot air drying

3D simulation of momentum, heat and mass transfer in potato cubes during intermittent microwave-convective hot air drying

Mathematical modeling and simulation of refractance window drying of mango pulp for moisture, temperature, and heat flux distribution

AbstractThis study aims to simulate the coupled heat and mass transfer during refractance window (RW) drying of mango pulp. A simulation model was developed by considering temperature and moisture‐dependent effective diffusivity. With the help of COMSOL Multiphysics, a three‐dimensional (3D) model was developed to solve heat and mass transfer equations. RW drying of mango pulp (6 mm thick) was executed at differe temperature of 75, 80, 85, and 90°C and air velocity of .7 m/s. There was a quick rise in product temperature, and it remained constant throughout the experiment. The drying time required to reduce mango pulp's moisture content from 5.33 to .25 (g water/g dry matter) ranged between 5.7 and 8.5 h during RW drying. Surface moisture was 28, 30, 31, and 33% lower than moisture content at the bottom of pulp after 15 min of drying when drying temperatures were 75, 80, 85, and 90°C, respectively. Diffusivity increases with increasing temperature, and values range from 2.50 × 10−10 to 3.68 × 10−10 m2/s. Out of six empirical models, page, modified page, and two‐term exponentials were the best fit for drying characteristics.Practical ApplicationsThis study explores the heat and mass transfer modeling and simulation of RW drying of mango pulp. The three‐dimensional (3D) model gave a better understanding and visualized the effect of different heat source temperature combinations on temperature profile and their distribution and moisture content and their distribution throughout the sample. The method and mode used for this experiment can enable many researchers to conduct experimental studies on RW drying products. Also, a simulation model is a precise tool for forecasting drying product characteristics, drying behaviors, and physicochemical changes during the drying process. Simulation applications for better designing processes in food industries shall be more in the coming future. The present finding can be used by food processors and researchers for predicting the drying dynamics and subsequent upscaling of the RW drying process at an industrial scale.

Boundary and Interface Treatments for One-Unit Pore-Scale Simulations of Heat and Mass Transfer in Porous Materials: A Mini-Review

Boundary and Interface Treatments for One-Unit Pore-Scale Simulations of Heat and Mass Transfer in Porous Materials: A Mini-Review

Non-invasive imaging of ion concentration distribution around cell spheroids by electrical impedance tomographic sensor printed on circuit board under temporal compensation by ion transport impedance model

A non-invasive imaging called as PCB-EIT imaging has been proposed in order to image spatio-temporal ion concentration distribution around cell spheroids in 0.1 s of temporal resolution by a newly developed electrical impedance tomographic sensor printed on circuit board (PCB-EIT sensor). To realize the high temporal resolution in PCB-EIT imaging, the temporal compensation by the ion transport impedance model interpolating the extracted resistance of extracellular solution Rex obtained from the Cole-Cole equation is employed. To confirm the performance of PCB-EIT imaging, the ion concentration distribution around three cell spheroid types (GFP type (GFPT), Histone type (HT) and wild type (WT)) which are electrically different due to green fluorescent protein expressed in cytoplasm and nucleus of MRC-5. As a result, spatio-temporal ion concentration distributions due to ion transport from cell spheroid are successfully reconstructed by PCB-EIT imaging. The images by PCB-EIT imaging are validated with those by fluorescence ratio imaging within the distribution error εdis of 0.046 ± 0.0038 in maximum. For an evaluation of the ion diffusivity Dm of each cell spheroid type by the mass transfer simulation based on Fick’s law, Dm of GFPT shows the highest value among the three cell types in the earlier time range from 4 s, while Dm of HT shows the highest one in the time range from 15 s, which indicates that PCB-EIT imaging is able to evaluate the ion transport characteristics of each cell type.

Modeling and Simulation of Photobioreactors with Computational Fluid Dynamics—A Comprehensive Review

Computational Fluid Dynamics (CFD) have been frequently applied to model the growth conditions in photobioreactors, which are affected in a complex way by multiple, interacting physical processes. We review common photobioreactor types and discuss the processes occurring therein as well as how these processes have been considered in previous CFD models. The analysis reveals that CFD models of photobioreactors do often not consider state-of-the-art modeling approaches. As a comprehensive photobioreactor model consists of several sub-models, we review the most relevant models for the simulation of fluid flows, light propagation, heat and mass transfer and growth kinetics as well as state-of-the-art models for turbulence and interphase forces, revealing their strength and deficiencies. In addition, we review the population balance equation, breakage and coalescence models and discretization methods since the predicted bubble size distribution critically depends on them. This comprehensive overview of the available models provides a unique toolbox for generating CFD models of photobioreactors. Directions future research should take are also discussed, mainly consisting of an extensive experimental validation of the single models for specific photobioreactor geometries, as well as more complete and sophisticated integrated models by virtue of the constant increase of the computational capacity.

The Numerical Simulation of Heat and Mass Transfer on Geothermal System-A Case Study in Laoling Area, Shandong, China

Geothermal resources have become increasingly attractive and promising because of their abundant resource base and environmental protection, especially for hydrothermal resources, which are widely developed for heating in winter. It is indicated that numerical simulation is an important tool for high efficiency geothermal system development. Compared with other methods, numerical simulation is a more comprehensive, scientific, and effective method in the evaluation of recoverable resources and the formulation of development plans. However, there are some problems in the existing software, such as deviation in physical property calculation, incomplete multifields coupling, and poor applicability for low-permeability reservoir and large-scale models. Therefore, based on the optimized multiphysics coupling mathematical model and MPI architecture, a simulator for a multiphysics-coupling geothermal system (SMG) was developed by Sinopec. A case study in the Laoling area, Shandong, China was primarily conducted by using geothermal software SMG, where the effect of well spacing and injection fluid temperature on the production was illustrated. Moreover, a geothermal recoverable resources evaluation method based on numerical simulation is proposed and used for the evaluation of regional geothermal dynamic recoverable resources in Laoling.

Statistical electromagnetics for industrial pharmaceutical lyophilization.

Lyophilization is a common unit operation in pharmaceutical manufacturing but is a prolonged vacuum drying process with poor energy utilization. Microwave-assisted vacuum drying has been investigated to accelerate the lyophilization process. However, the literature lacks methodical approaches that consider the lyophilizer, the lyophilizate, the microwave power uniformity, the resulting heat uniformity, and the scalability. We present a microwave-vacuum drying method based on the statistical electromagnetics theory. The method offers an optimum frequency selection procedure that accounts for the lyophilizer and the lyophilizate. The 2.45GHz frequency conventionally utilized is proven to be far from optimum. The method is applied in a microwave-assisted heating configuration to pharmaceutical excipients (sucrose and mannitol) and different myoglobin formulations in a lab-scale lyophilizer. At 18GHz frequency and 60W microwave power, the method shows nearly three times speed-up in the primary drying stage of sucrose relative to the conventional lyophilization cycle for typical laboratory batches. The uniformity of the microwave power inside the chamber is controlled within ± 1 dB. The resulting heating uniformity measured through residual moisture analysis shows 12.7% of normalized SD of moisture level across the batch in a microwave-assisted cycle as opposed to 15.3% in the conventional cycle. Conventional and microwave lyophilized formulations are characterized using solid-state hydrogen-deuterium exchange-mass spectrometry (ssHDX-MS), solid-state Fourier transform infrared spectroscopy (ssFTIR), circular dichroism (CD), and accelerated stability testing (AST). Characterization shows comparable protein structure and stability. Heat and mass transfer simulations quantify further effects of optimal volumetric heating via the high-frequency statistical microwave heating.