Mass Transfer Effects Research Articles

Model-based design of gradient elution in liquid-liquid chromatography: Application to the separation of cannabinoids

Liquid-liquid chromatography (LLC) is a separation technique that utilizes a biphasic solvent system as the mobile and stationary phases. The components are separated solely due to their different distributions between the two liquid phases. Gradient change in the mobile phase composition during the chromatographic process is a powerful method for improving the resolution of separation or shortening the process time. Gradient elution readily applies to LLC with biphasic solvent systems in which the stationary phase composition remains nearly constant when the mobile phase composition changes. This work proposes a model-based approach to optimize gradients in LLC and circumvent tedious trial-and-error experiments. The solutes’ distribution constant depends on the mobile phase composition. Thus, the distribution constants were described as a function of the content of one of the solvents (= modifier) in the mobile phase. The dispersive and mass-transfer effects in the tubing and the column are modeled with a stage model. Only a few experiments are required to determine the model parameters. After the validation of the model and its parameters, the model can be used for LLC gradient optimization. The proposed approach was demonstrated for a gradient LLC separation of a mixture of four cannabinoids. Two different gradient shapes, one-step and linear gradient, were considered. For a pre-selected minimal purity requirement, the gradient was optimized for maximum process efficiency, defined as the product of productivity and yield. An experiment conducted with the optimized gradient conditions was in good agreement with the simulation, showing the potential of the proposed method.

Efficient estimation of gas exchange and respiration kinetics in apple using pathlength-resolved GASMAS

Optimization of controlled atmosphere (CA) storage of pome fruit crucially depends on understanding of respiratory gas exchange. Different fruit properties are involved in describing gas transfer and respiration kinetics, which can vary between cultivars, fruit batches and individual fruit. Determination of these properties currently requires a combination of different time-consuming techniques and data analysis procedures. This study introduces a more efficient single method for O2 gas exchange characterization of fruit based on the non-destructive pathlength-resolved GASMAS (gas in scattering media absorption spectroscopy) technique. GASMAS was used to measure the absolute intercellular O2 concentration in fruit of different apple cultivars (Malus x domestica Borkh.) with distinct porosity including 'Jonagold', 'Braeburn', and 'Nicoter'. To resolve the ambiguity between variation in pathlength and O2 concentration inherent to GASMAS, the pathlength travelled through pores cavities was quantified through a second GASMAS measurement at the absorption line of H2O vapour. Dynamic experiments were then performed in which the fruit was subjected to varying external O2 concentrations while measuring the internal O2 response. The observed dynamic profiles of external and internal O2 concentration were fitted with a lumped -respiration model to estimate the effective mass transfer coefficient, maximum respiration rate and Michaelis Menten constant of intact fruit. The model showed a good fit (R2>0.95) with the measured data and reliable estimates for the model parameters. The proposed method provides a novel and more efficient way to estimate the gas exchange properties of fruit that are essential for optimizing CA storage conditions. Future challenges for the proposed method are with applications to other gasses such as CO2 and ethylene.

Soret effect on stability of Darcy problem in a bidispersive porous medium with an exothermic chemical surface reaction

AbstractWe examine a saturated bidispersive porous medium undergoing an exothermic chemical reaction at its lower boundary. The fluid flow within this medium is modelled using the Darcy approach. While the Dufour effect is disregarded, the influence of the Soret effect is thoroughly explored. This problem represents a complex multiphysical phenomenon that integrates fluid dynamics, heat and mass transfer, chemical kinetics and thermoelectric effects. This problem finds relevance in various scientific and engineering applications, including enhanced oil recovery, chemical engineering, environmental engineering and energy systems. We introduce a complementary energy theory alongside a linear theoretical framework for the model. The Chebyshev collocation method is employed to derive both linear and nonlinear results. Our findings reveal that the effect of enhancing the Soret coefficient on the system's stability is contingent upon the boundary conditions and the Lewis number. Specifically, an increase in the Soret coefficient generally stabilises the system during stationary convection. Conversely, in scenarios where oscillatory convection prevails, a higher Soret coefficient tends to destabilise the system.

Calculation and numerical modeling of the effect of heat and mass transfer on the properties of pile foundations in seasonally freezing soils

The phenomenon of heat and mass transfer in seasonally freezing soils has a significant impact on the condition of pile foundations. Building structures constructed in such soils experience extremely negative consequences: frost heave, vibration dynamics, moisture mass transfer and soil weakening during the thawing. Seasonally freezing soils occupy most of the territory of Kazakhstan, and in most regions the depth of soil freezing exceeds 1.5 m, there are settlements where the index reaches 1.97 m (Semiyarka, East Kazakhstan region) and in the north of the country - 2.74 m (Arshaly, Akmola region). Arrangement of foundation bases below the frost depth leads to increased construction costs, requires additional costs for thermal insulation, ventilation, other materials and structures, and, in addition, does not always lead to a full levelling of the negative impact of heat and mass transfer on the term and conditions of operation of buildings, structures, railways and roads. Therefore, the efforts of engineers and specialists in the field of thermal physics are aimed at finding effective ways to solve the problems of deformation and destruction of foundations in seasonally freezing soils. In the article an attempt is made to reveal the character of heat and mass transfer influence on pile foundations in seasonally freezing soils on the basis of a thermomechanical model.

Bubble Turbulent Gas-Permeable Membrane for Ammonia Recovery from Swine Wastewater: Mass Transfer Enhancement and Antifouling Mechanisms.

Recovering ammonium from swine wastewater employing a gas-permeable membrane (GM) has potential but suffers from the limitations of unattractive mass transfer and poor-tolerance antifouling properties. Turbulence is an effective approach to enhancing the release of volatile ammonia from wastewater while relying on interfacial disturbance to interfere with contaminant adhesion. Herein, we design an innovative gas-permeable membrane coupled with bubble turbulence (BT-GM) that enhances mass transfer while mitigating membrane fouling. Bubbles act as turbulence carriers to accelerate the release and migration of ammonia from the liquid phase, increasing the ammonia concentration gradient at the membrane-liquid interface. In comparison, the ammonium mass transfer rate of the BT-GM process applied to real swine wastewater is 38% higher than that of conventional GM (12 h). Through a computational fluid dynamics simulation, the turbulence kinetic energy of BT-GM system is 3 orders of magnitude higher than that of GM, and the effective mass transfer area is nearly 3 times that of GM. Seven batches of tests confirmed that the BT-GM system exhibits remarkable antifouling ability, broadens its adaptability to complex water quality, and practically promotes the development of sustainable resource recycling.

Thermoelastic diffusion in nonlocal orthotropic medium with porosity

The present article investigates the linear theory of nonlocal thermoelasticity in homogeneous orthotropic porous medium with diffusion in the context of dual-phase-lag model. The focal point of the present study involves an examination of Fick’s mass diffusion law and the generalized Fourier’s law within the context of the dual-phase-lag model of hyperbolic thermoelasticity. The incorporation of voids, mass diffusion with phase lagging in the diffusion flux is the basis for establishing the void diffusion-elasticity models. Furthermore, the new dual-phase-lag diffusion model introduces the consideration of nonlocal effects in mass transfer. The resolution of the problem involves the utilization of normal mode analysis, employed for solving, and encompasses the application of thermal shock at the surface boundary. Numerical calculations of stress components, displacement components, voids, temperature, and concentration of the diffusive material are performed for various distances and time intervals.

Optimization of a Rare Earth and Aluminum Leaching Process from Weathered Crust Elution-Deposited Rare Earth Ore with Surfactant CTAB

Ammonium sulfate is typically employed as a leaching agent in the in situ leaching of weathered crust elution-deposited rare earth ore. However, it is associated with challenges such as low efficiency in mass transfer for rare earth (RE) leaching, high usage of the leaching agent, and prolonged leaching duration. To address the issues mentioned above, the surfactant cetyltrimethyl ammonium bromide (CTAB) was compounded with 2% ammonium sulfate to form a leaching agent in this paper. The effects of CTAB concentration, temperature, pH, and leaching agent flow rate on the rare earth (RE) and aluminum (Al) leaching mass transfer process from RE ore were investigated using chromatographic plate theory. The results revealed that CTAB addition improved the RE mass transfer process while moderately inhibiting the Al mass transfer efficiency. Increasing the temperature and pH of the leaching solution led to higher theoretical plate numbers for RE and Al leaching, lowered theoretical plate height (HETP), and enhanced leaching mass transfer efficiency. However, under high temperature and alkaline conditions, the mass transfer efficiency begins to decrease, indicating that high temperature and alkaline conditions are not conducive to the synergistic enhancement of RE and Al leaching by CTAB. Considering that clay minerals have good pH buffering properties, adjusting the pH of the leaching solution during rare earth ore leaching operations was deemed unnecessary. The optimal mass transfer conditions for leaching RE and Al were identified as 2% ammonium sulfate concentration, 0.00103 mol/L CTAB concentration, pH range of 5.2–5.5 for the leaching solution, 0.6 mL/min leaching solution flow rate, and room temperature. The rare earth leaching mass transfer effect could be enhanced during summer operations.

Enhanced treatment of p-nitrophenol and coking wastewater through electrochemical and electrochemical-ozonation coupling process utilizing a novel Ti4O7 reactive electrochemical membrane anode

Organic pollutants in water could be removed by electrochemical treatment using a reactive electrochemical membrane (REM) with Magnéli phase Ti4O7, yet it is challenging to design suitable porosity to realize effective mass transfer and enhance the reactivity. Here, a novel Ti4O7 REM was prepared by a spark plasma sintering (SPS) method, which showed excellent electrochemical reactivity and mass transfer rate for organic pollutants in water. Compared to other Ti4O7 REMs, the novel Ti4O7 REM achieved a 140–9000-fold decrease in charge transfer resistance and a 5–110-fold increase in mass transfer rate. The p-nitrophenol in water can be completely removed in the REM system, with a maximum total organic carbon (TOC) removal rate of 85%. Then the REM system obtained an amazing removal rate of TOC (50.1%) and UV254 (89.6%) in the electrochemical treatment of real coking wastewater. In addition, to further enhance the removal efficiency, a coupled oxidation process with the novel Ti4O7 REM and O3 aeration was investigated. The TOC removal rate and energy consumption were 57.1% and 165.2 kWh (kg TOC)−1 at the optimal conditions within a short treating time. Our findings highlighted an innovative REM for a broad range of potential environmental applications.

Method for controlling the area of the electrolyte outlets in the flow field simulation and experimental verification of electrochemical machining

Electrochemical machining (ECM) is regarded as a promising and cost-effective manufacturing method for difficult-to-cut materials with complex shapes and structures. Many methods have been successfully developed for the flow field state of machining gaps, which is a key factor affecting machining performance in ECM engineering practice. However, little attention has been given to the area of the electrolyte outlets. This study attempts to present a method for controlling the area of the electrolyte outlets in the flow field simulation and experimental verification of electrochemical machining. The simulation results indicate that the convergent outlet mode can effectively enhance the turbulent effect of the fluid in the inter-electrode gap, especially in the near-wall region, and improve the mass transfer effect of electrolyte. Meanwhile, the simulation results also showed that better material removal rate (MRR) and surface roughness can be obtained when the convergent degree is about 50–70% combined with the effects of bubble volume compression and flow velocity reduction. The experimental results confirmed that the convergent outlet mode can obtain better MRR and surface roughness. Energy-dispersive X-ray spectroscopy results of machined specimens showed that oxides with strong adhesion on the specimen’s surface were effectively eliminated due to stronger turbulence effect under convergent outlet conditions. This should be considered as the main reason for improving machining performance by changing the electrolyte outlet area. These conclusions can provide some useful assistance for ECM engineering practice.

Thermo-solutal convective conditions impact in dual stratified stagnation-point flow of second-grade (SG) fluid with chemical reaction

In various engineering and industrial utilizations, the heat-mass transportation concept has been rigorously witnessed, for illustration air conditioning of room, nuclear reactors cooling and abundant other realistic conditions. This scrutiny elaborates buoyancy-driven viscoelastic magnetized flow configured by stretched vertical surface. Heat-transfer effects are explored through Ohmic dissipations and radiation aspects. Chemical reaction characteristics are deliberated to address the mass-transfer effects. In addition, the stratification phenomenon together with Robin conditions is introduced. Mathematical systems are simplified under BLT (boundary-layer theory). Non-dimensional analysis is done by introducing similarity variables. Homotopic criteria is utilized to compute convergent solutions. Consequence of controlling variables emerging in non-dimensional problem is analyzed via pictorial and tabular illustrations. It is evident that temperature field together with heat transference rate are enlarged when radiation and thermal Biot parameters are augmented.

Adsorption of stable and labile emerging pollutants on activated carbon: degradation and mass transfer kinetic study

The design of adsorption processes for pharmaceuticals removal depends not only on the adsorption equilibrium but also on the mass transfer and adsorbate stability, being a problem still not solved the case of degradation products. By selecting different stable (amoxicillin, ciprofloxacin, carbamazepine and ibuprofen) and labile micropollutants (omeprazole) as case studies emerging pollutants, we have quantitatively analysed these effects on activated carbon. For stable compounds, the experimental data were fitted to equilibrium models to obtain information about the different adsorption mechanism depending on the characteristics of the molecules. Mass transfer effects were analysed for all the adsorbates, observing the control of intraparticle pore diffusion mechanism, since the effective pore diffusion coefficient is in the range from 10–8 to 10–10 cm2 h−1. As far as omeprazole is concerned, a kinetic model is proposed for predicting its degradation, identifying the reversibility of several degradation steps. The overall adsorption of OMP and derivates is calculated, observing the pore diffusion is considered as the rate-limiting step. For the first time, a combined model considering the chemical degradation and the adsorption of the degradation products is proposed and experimentally validated. This represents an important step in the modelling of processes leading to the purification of water from this type of pollutant.

Research and Optimization of Four Serpentine-Wave Flow Fields in PEMFC

The layout of the cathode flow field largely determines the net output power of the proton exchange membrane fuel cell (PEMFC). To make the normal mass transfer effect best, the longitudinal channel was waved based on four serpentine flow channels, and the effects of sag depth and longitudinal channel width on the output efficiency of the cell were explored. The results show that the wave channel design systematically enhances the forced convection between adjacent channels, which can prevent a large zone of oxygen starvation zone at the outlet of the channel. The increase of the normal velocity in the gas transmission process will inevitably induce a significant enhancement of the mass transfer effect and obtain a higher current density in the reaction zone. For the longitudinal channel width, it is found that increasing its size in the effective range can greatly reduce the channel pressure drop without reducing the output power, thereby improving the overall efficiency. When the sag depth and longitudinal channel width gradient are 0.6 mm and 0.2 mm respectively, PEMFC can obtain the best comprehensive performance.

Deep‐bed drying kinetics and thermodynamic parameters of high‐moisture parboiled paddy (ASD‐16) in a reversible airflow fixed bed dryer

AbstractReversible airflow fixed bed dryer (RAFBD) is an energy‐efficient, cost‐effective, and dependable dryer for using renewable energy sources in parboiling mills. In this study, a medium‐sized and high‐moisture parboiled paddy, ASD‐16, was dried in the RAFBD to determine its deep drying characteristics and thermodynamic properties. The chosen paddy variety is a commonly cultivated paddy in the southern region of Tamil Nadu, India. The RAFBD experimental setup was designed to dry 30 kg of parboiled paddy. For the statistical analysis, the experimental data for the deep‐bed drying at hot air temperatures 50–80°C and velocities of 0.1 and 0.15 m/s were used at constant specific humidity. To predict drying characteristics, 12 drying models were compared. Based on their statistical parameters, the Midilli et al. model was selected. For the tested conditions, the coefficients for effective moisture diffusion, heat transfer, and mass transfer were between 9.82 × 10−8 and 2.13 × 10−7 m2/s, 0.3802 and 1.325 W/m2 K, and 0.375 × 10−4 and 1.26 × 10−4 m/s, respectively. Furthermore, the determined activation energy ranged from 20.4964 to 20.4390 kJ/mol.Practical ApplicationsASD‐16 is one of the popular paddy varieties cultivated and used in parboiling mills in the study region. The outcome of this research can contribute to the application of a cost‐effective dryer for drying high‐moisture paddy. Furthermore, the drying time and bed height proposed in this work can reduce the drying time in the mills and improve energy efficiency. The drying kinetics and suitability of the models found in this study will contribute to the design and development of low‐cost dryers for the local parboiling industries. As rice husk, which is a waste from paddy processing, is used for the heating process, industries can reduce the cost of energy for closed‐roof drying. This study provides a clear insight to the researchers and designers in standardizing the capacity of the dryer, drying temperature, and airflow rate for any similar kind of paddy variety.

Computer Simulation of Heat and Mass Transfer Effects on Nanofluid Flow of Blood Through an Inclined Stenosed Artery With Hall Effect

Abstract The present study deals with the analysis of heat and mass transfer for nanofluid flow of blood through an inclined stenosed artery under the influence of the Hall effect. The effects of hematocrit-dependent viscosity, Joule heating, chemical reaction and viscous dissipation are taken into account in the governing equations of the physical model. Non-dimensional differential equations are solved using the finite difference method, by taking into account the no-slip boundary condition. The effects of different thermophysical parameters on the velocity, temperature, concentration, shear stress coefficient and Nusselt and Sherwood numbers of nano-biofluids are exhaustively discussed and analysed through graphs. With an increase in stenosis height, shear stress, the Nusselt number and the Sherwood number are computed, and the impacts of each are examined for different physical parameters. To better understand the numerous phenomena that arise in the artery when nanofluid is present, the data are displayed graphically and physically described. It is observed that as the Hartman number and Hall parameter increase, the velocity drops. This is as a result of the Lorentz force that the applied magnetic field has generated. Blood flow in the arteries is resisted by the Lorentz force. This study advances the knowledge of stenosis and other defects’ non-surgical treatment options and helps reduce post-operative consequences. Moreover, ongoing research holds promise in the biomedical field, specifically in magnetic resonance angiography (MRA), an imaging method for artery examination and anomaly detection.

Tempospatially Confined Catalytic Membranes for Advanced Water Remediation.

The application of homogeneous catalysts in water remediation is limited by their excessive chemical and energy input, weak regenerability, and potential leaching. Heterogeneous catalytic membranes (CMs) offer a new approach to facilitate efficient, selective, and continuous pollutant degradation. Thus, integrating membranes and continuous filtration with heterogeneous advanced oxidation processes (AOPs) can promote thermodynamic and kinetic mass transfers in spatially confined intrapores and facilitate diffusion-reaction processes. Despite the remarkable advantages of heterogeneous CMs, their engineering application is practically restricted due to the fuzzy design criteria for specific applications. Herein, the recent advances in CMs for advanced water remediation are critically reviewed and the design flow for tempospatially confined CMs is proposed. Further, state-of-the-art CM materials and their catalytic mechanisms are reviewed, after which the tempospatial confinement mechanisms comprising the nanoconfinement effect, interface effect, and kinetic mass transfer are emphasized, thus clarifying their roles in the construction and performance optimization of CMs. Additionally, the fabrication methods for CMs based on their catalysts and pore sizes are summarized and an overview of their application and performance evaluations is presented. Finally, future directions for CMs in materials research and water treatment, are presented.

Investigation on the propagation characteristics of pressure wave during managed pressure drilling

The small difference between formation pressure and fracture pressure in offshore oil and gas reservoirs poses a huge challenge to drilling. Managed pressure drilling (MPD) technology, as a drilling technique that can accurately control bottomhole pressure, is an effective technique to solve this challenge. In MPD technology, the pressure wave propagation behavior and mechanism in the wellbore induced by wellhead backpressure are crucial for parameter design and efficient application. In this paper, pressure wave propagation characteristics and mechanism in gas-liquid flow were investigated with a new proposed pressure wave velocity model that considers inter-phase mass transfer effect. This new model and its solution algorithm were verified with experimental data in literature. The influence of gas invasion stage, drilling fluid type, drilling fluid density and backpressure on pressure wave propagation characteristics were investigated. Results show that the time for pressure wave induced by wellhead backpressure in the wellbore cannot be ignored in the design of the backpressure value during MPD. This propagation time increases with occurrence of gas invasion. Moreover, the propagation time in water-based drilling fluid is longer than that in oil-based drilling fluid, which is because the interphase mass transfer between invaded gas and oil-based drilling fluid. The influence mechanism of high drilling fluid density and wellhead backpressure on pressure wave propagation characteristics is due to the suppression of gas invasion process. These findings could be used as guides in parameters design and optimization in MPD.

Biomimetic hybrid porous microspheres with plant membrane-wall structure for evaluating multiscale mechanisms of ultrasound-assisted mass transfer

Determination of mass transfer during ultrasound-assisted extraction (UAE) has always been a challenge, not to mention the novel breakthrough of mechanisms for its positive effects. Herein, versatile porous microspheres (PM) with membrane-wall structure like plant tissues, which were made from sodium alginate/polyacrylamide dual crosslinking gels loaded with liposomes, were prepared to reveal the micro mass transfer effects during UAE. Results showed that prepared PM kept stable microstructure during extraction and ultrasound significantly accelerated the pore diffusion rather than surface diffusion. This effect resulted in higher UAE efficiency of PM with 60 % porosity than solid microspheres (143.72 to 155.47 mg/L), and the finding can be further explained as the accelerated internal diffusion (14.25 %) under ultrasound treatment. Moreover, multi-physics coupling simulations were performed to elucidate the enhanced pore flow and UAE efficiency. Acoustic streaming induced by cavitation effect increased the seepage velocity within the PM, and the pore structure would undergo compression and expansion deformation with alternated acoustic pressure due to its elastic characteristic. Both microscale effects improved the mass transfer and increase the UAE efficiency without structural damage from cavitation. This study fills the UAE mechanisms from micro view and provides a novel method for the study of vital micro processes.

Lie symmetry based neural networking analysis for Powell–Eyring fluid flow with heat and mass transfer effects

Heat exchangers, drying, dehydration, pollutant dispersion, separation processes, and biological individualities to name a few are significant phenomena in numerous fields and industries subject to both mass transfer and heat transfer aspects. Owing to such importance the aim of the present study is to offer a machine learning remedy for mass transfer rate at the surface subject to the Powell–Eyring (PE) fluid model. The flow field is rooted with suction and injection effects. The heat transfer aspects are considered by using the energy equation. The developed differential system is reduced by using Lie symmetry and the shooting scheme is used to get numerical data corresponding to four inputs namely suction parameter, PE fluid parameter, Schmidt number, and power law index. Levenberg–Marquardt backpropagation-based neural networking model is developed along with MSE and regression analysis to approximate the ShD number. It is observed that the mass transfer rate shows inciting values towards the suction parameter, Schmidt number, and concentration power law index. Further, the magnitude of Powell–Eyring fluid concentration is higher in the case of injection.

Interfacial Heat and Mass Transfer Effects on Secondary Hydrate Formation under Different Dissociation Conditions

Interfacial Heat and Mass Transfer Effects on Secondary Hydrate Formation under Different Dissociation Conditions

Mesoporous carbon spheres with programmable interiors as efficient nanoreactors for H2O2 electrosynthesis

The nanoreactor holds great promise as it emulates the natural processes of living organisms to facilitate chemical reactions, offering immense potential in catalytic energy conversion owing to its unique structural functionality. Here, we propose the utilization of precisely engineered carbon spheres as building blocks, integrating micromechanics and controllable synthesis to explore their catalytic functionalities in two-electron oxygen reduction reactions. After conducting rigorous experiments and simulations, we present compelling evidence for the enhanced mass transfer and microenvironment modulation effects offered by these mesoporous hollow carbon spheres, particularly when possessing a suitably sized hollow architecture. Impressively, the pivotal achievement lies in the successful screening of a potent, selective, and durable two-electron oxygen reduction reaction catalyst for the direct synthesis of medical-grade hydrogen peroxide disinfectant. Serving as an exemplary demonstration of nanoreactor engineering in catalyst screening, this work highlights the immense potential of various well-designed carbon-based nanoreactors in extensive applications.