Mass Transfer Phenomena Research Articles

In-Depth Kinetic Modeling and Chemical Analysis for the Epoxidation of Vegetable Oils in a Liquid–Liquid–Solid System

A heterogeneous catalyst for producing epoxidized vegetable oils, an important intermediate in the production of non-isocyanate polyurethanes, is essential for product separation and for decreasing the side-reaction, i.e., ring-opening reaction, via the Prileschajew method. The development of reliable kinetic models considering key variables for both phases and the mass transfer phenomena is missing in the literature. The reaction pathway for the ring-opening reaction is also under debate. Therefore, we studied the kinetics of epoxidation of cottonseed oil by perpropionic acid over the solid acid catalyst amberlite IR-120. An in-depth kinetic model was developed by using Bayesian inference. The reaction pathway for the ring opening was investigated. Propionic acid, a weak acid, allows for a decrease in the oxirane ring-opening side reaction.

A Review on Numerical Simulation of Hydrogen Production from Ammonia Decomposition

Ammonia (NH3) is regarded as a promising medium of hydrogen storage, due to its large hydrogen storage density, decent performance on safety and moderate storage conditions. On the user side, NH3 is generally required to decompose into hydrogen for utilization in fuel cells, and therefore it is vital for the NH3-based hydrogen storage technology development to study NH3 decomposition processes and improve the decomposition efficiency. Numerical simulation has become a powerful tool for analyzing the NH3 decomposition processes since it can provide a revealing insight into the heat and mass transfer phenomena and substantial guidance on further improving the decomposition efficiency. This paper reviews the numerical simulations of NH3 decomposition in various application scenarios, including NH3 decomposition in microreactors, coupled combustion chemical reactors, solid oxide fuel cells, and membrane reactors. The models of NH3 decomposition reactions in various scenarios and the heat and mass transport in the reactor are elaborated. The effects of reactor structure and operating conditions on the performance of NH3 decomposition reactor are analyzed. It can be found that NH3 decomposition in microchannel reactors is not limited by heat and mass transfer, and NH3 conversion can be improved by using membrane reactors under the same conditions. Finally, research prospects and opportunities are proposed in terms of model development and reactor performance improvement for NH3 decomposition.

A mathematical analysis of mass transfer phenomena with chemical reaction over the flow of Sisko ferronanofluid across a permeable surface

Mathematically study mass transfer phenomena involving chemical reactions in the flow of Sisko Ferro nanofluids through the porous surface. Three ferronano particles, manganese-zinc ferrite (Mn1/2Zn1/2Fe2O4), cobalt ferrite (CoFe2O4), and nickel–zinc ferrite (Ni–Zn Fe2O4) are considered with water (H2O) and ethylene glycol (C2H6O2) as base liquids. Appropriate resemblance transitions are used to convert the governing system of a nonlinear PDE to a linear ODE. The Runge–Kutta method, as extended by the shooting technique, is used to accomplish the reduction governing equations. The effects of various associated parameters on fluid concentration and mass transfer rate are investigated: magnetic criterion (M), Siskofluid material factor (A), Solid volume fraction (ϕ) for nanofluids, permeability parameter (Rp), Chemical reaction criterion (γ), Brownian motion factor (Nb), and Thermophoretic parameters (Nt). The current findings indicate that the diffusion proportion of Sisko Ferronanofluid Ni–Zn Fe2O4–H2O and CoFe2O4–H2O is higher than that of Ni–Zn Fe2O4–C2H6O2 and CoFe2O4–C2H6O2 respectively but it is opposite in the case of Mn–Zn ferrite. The comparison study was carried out to validate the precision of the findings.

A PBM-Based Procedure for the CFD Simulation of Gas–Liquid Mixing with Compact Inline Static Mixers in Pipelines

A compact static mixer for gas–liquid dispersion in pipelines is studied in this paper with a Reynolds averaged two fluid model approach. A procedure based on the lumped parameter solution of a population balance model is applied to obtain the bubble Sauter mean diameter needed to model the interphase forces. The gas distribution in the pipe is analyzed in two different operative conditions and the efficiency of the static mixer is assessed in terms of the gas homogeneity in the pipe section, with low coefficients of variations being obtained. A computational model to obtain the volumetric mass transfer coefficient, kLa, developed for partially segregated systems is applied finding kLa values comparable to those typically obtained with other static mixers. The proposed computational model allows us to locally analyze the oxygen transfer rate by observing the limitations due to gas accumulation behind the body of the static mixer, which leads to the local depletion of the driving force. Geometrical optimization of the static element is proposed, based on the analysis of gas–liquid fluid dynamics and of the interphase mass transfer phenomena.

Lubricated surface oblique stagnation point flow of second-grade fluid with heat and mass transfer phenomenon: applications to hydraulic systems

The lubrication phenomenon with heat and mass transfer phenomenon justified applications in ploy engineering, polymer processes, compressor oils, piston oils, hydraulic systems, and paint industries. This contribution attributes the significance of heat and mass transfer due to the lubricated surface. The enhancement in the lubricated phenomenon is further suggested by incorporating the nonlinear radiative impact and chemical reaction. The viscoelastic fluid flow is confined in the zone of stagnation point of the lubricated surface. The axial and tangential velocities are presented for no-slip and full-slip cases. Moreover, a comparative analysis is carried out for temperature distribution over lubricated and non-lubricated surfaces for linear and nonlinear radiations. The problem is modeled in view of fundamental conservation laws, and the similarity variables are used to transfer them to the system of coupled nonlinear boundary value problem which is approximated by the Keller box method. The obtained results are validated with the existing literature as a particular case of the present study. It is noted that the local Nusselt number and Sherwood number are reduced by decreasing the efficiency of the lubricant also the nonlinear thermal radiation assists the heat transfer rate. The increase in chemical reaction declined the concentration phenomenon.

Modeling of ternary mixture of VOCs in photocatalytic oxidation reactor for indoor air quality application

Photocatalytic oxidation (PCO) is an innovative method of removing volatile organic compounds (VOCs) from indoor air. PCO technology employs a semiconductor (such as TiO2) and ultraviolet light to decompose VOCs via successive oxidation processes and creates CO2 and H2O as the ultimate products of complete mineralization. The greatest drawback of this technology is, however, the production of hazardous by-products. The possible health risk posed by hazardous by-products inhibits the commercial adoption of PCO-based air purifiers in the indoor environment. Modeling is a powerful tool to address the chemical interaction and mass transfer phenomenon in the PCO reactor. This study presents the modeling of a ternary mixture of VOCs and generated by-products using a proposed degradation reaction pathway. A one-dimensional mathematical model by considering the axially dispersed plug flow and Langmuir-Hinshelwood (L-H) based reaction rate as well as linear source spherical emission model (LSSE) for the irradiation distribution on the media surface were used for modeling of VOCs and by-products. Three VOCs from different chemical groups (aldehyde, ketone, aromatic groups) were chosen as challenge compounds, and a commercial PCO filter (TiO2 coated on silica fiber felts) was considered as a photocatalyst. The model prediction was performed at different levels of concentration (0.1–1 ppm), relative humidity (15–70%), air velocity (0.016–0.1 m/s), and light intensity (7–23W/m2). Among generated by-products, aldehydes were the major by-products of VOCs in the PCO reactor. It was revealed that increasing concentration and irradiation, as well as decreasing relative humidity and velocity, increases by-product generation.

Honey Crystallization, Myth and Microscopical Characterization

Honey is a sweet liquid food with high nutritional value, and provides immense health benefits. It is highly concentrated with sugar and contains mostly glucose and fructose. Pollens are also embedded naturally in the honey, and pollen contains protein and amino acids. These proteins and amino acids are essential for life-saving. The presence of pollens within honey samples may be a sign of natural characteristics and further, we can differentiate and define mono and multi-floral origin. Crystallization is a mass transfer phenomenon that leads to creation of a solid-liquid interface and results in a positive contribution to free energy of the nucleation. Crystallization of honey will affect its quality appearance, as well as consumers’ acceptability. This research was conducted with the aim to study the microscopic characteristics and crystallization behavior of different honey. About 50 out of 500 honey samples were studied for the presence and percentage of Mustard (Brassica spp) pollen and other types of pollen grains. Out of 50 honey samples, 41 were recorded with Mustard pollens, and 18 were recorded with high crystallization, 11 were in the initiation phase, 03 are non-crystallized and the rest 09 honey samples were recorded without crystallization. Interestingly, 09 samples that were recorded without Mustard pollen are also non-crystallized. Significantly, 09 honey samples were recorded without Mustard pollens. This study has suggested that the crystallization behavior is a natural process influenced by some types of nectar and pollens.

How mass and heat transfers could affect chitosan membrane formation via an enzymatic gelation

Herein, a 1D numerical model was developed to simulate the enzymatic gelation of chitosan in thin film geometry, corresponding to a thin polymer solution cast onto a support. Mass and heat transfer phenomena were taken into account in the mathematical model and coupled to the chemical reactions involved during the chitosan gelation process (urea hydrolysis, equilibrium reactions, deprotonation of chitosan). External mass transfers involving water and ammonia evaporation as well as carbon dioxide intake and evaporation (depending on the gelation process stage) were integrated in the model. A comparison was done in deep cell geometry between the numerical results obtained with the 1D and a 0D model developed and validated in a previous work. The 1D model was then able to predict the influence of the external transfers on the chitosan gelation kinetics. More precisely the model developed herein exhibited that minimum initial concentrations of urease and urea are necessary to reach the advanced gelation pH during the process, which is a prerequisite for preparing thin chitosan membrane.

Liquefaction, cracking and hydrogenation of microalgae biomass resources to CO2 negative advanced biofuels: Mechanisms, reaction microkinetics and modelling

Deoxygenation of triglycerides is one of the crucial pathways for the production of oxygen-free hydrocarbons and biofuels that are fully compatible with conventional internal combustion engines. The one-step liquefaction and hydrotreatment of Chlorella sorokiniana microalgae was investigated in a three-phase slurry reactor. The production of diesel-like hydrocarbons was successfully accomplished over sulfide form of NiMo/Al2O3 catalyst under hydrogen atmosphere. The present work contains a comprehensive investigation of the temperature and hydrogen pressure influence on the final product composition. The highest yield of C18 and C16 (26.1% and 10.7%, respectively) was reached by increasing the reaction temperature to 350 °C and hydrogen pressure to 50 bar, while at milder conditions (200 °C and 20 bar) the products appeared only in trace concentrations. In order to obtain an accurate kinetic model, reaction mechanism was first needed to be determined based on experimentally obtained products and intermediates. A simplified reaction pathway contains liquefaction, hydrogenolysis, hydrodeoxygenation, decarboxylation and decarbonylation. The model comprises mass transfer phenomena involved in the liquefaction process, the mass transfer of hydrogen from gas to liquid phase, adsorption, desorption and surface reaction kinetics. The lowest rate constant was calculated for the microalgae conversion to triglycerides (k0 = 1.93 × 10−6 min−1), indicating slow liquefaction.

Heat and mass transfer phenomenon for micropolar nanofluid with microrotation effects: Nonsimilarity simulations

Nonsimilar equations exist in many fluid flow problems and these equations are difficult to be solved using variation of the physical parameters. The key purpose of this study is to find nonsimilarity solution of nanofluid on an exponentially shrunk sheet in the existence of micropolar nanofluid without considerations of the thermal radiation and viscous dissipation effects. The governing partial differential equations (PDEs) are transformed into nonsimilar equations consisting of both ordinary and PDEs. Numerical results of velocity, microrotation, heat and concentration are presented in graphs. The results reveal that fluid particles’ velocity decreases nearby surface and increases afterward. The skin friction, heat and concentration transfer rate are also plotted to perceive the phenomena with different physical situations. It can be deduced that wall shear force [Formula: see text] is improved by developed effects of micropolar fluid parameter [Formula: see text] and reduced by increasing values of Hartmann number [Formula: see text].

Numerical analysis of thermal-hydraulic safety for a reactor containment in the event of a main steam line break

The present work demonstrates the development of a numerical thermal-hydraulic (TH) model for the containment module of the PRABHAVINI code which is an in-house severe accident analysis computer code used for the analysis of Indian pressurized heavy water reactors (PHWRs). The model, for the analysis of the TH behavior of the containment under a postulated main steam line break (MSLB) situation inside it, incorporates the effect of nonlinear coupling among different heat and mass transfer chronologies such as heat transfer within the containment and through its walls, wall and interface condensations, condensation due to over saturation of the air and evaporation.The TH model accounts for the thermodynamic non-equilibrium between the air–vapor mixture inside the containment and the water likely to be accumulated at the bottom of the containment.For the comparison of the TH model developed, a more conservative case study is undertaken where a single containment is analyzed for an MSLB accident ceasing the possibility of any kind of leakage from it. The results obtained from the model developed are compared with those obtained from the RELAP5. Next, the model is extended for more realistic TH analysis of the multi-volume containment incorporating the possibility of uni- or bi-directional inter-volume leakages as well as leakages from the containment volumes to the atmosphere. The analysis demonstrates the effect of different heat and mass transfer phenomena on the critical TH field variables of the reactor containment for the MSLB situation under consideration.

Variable chemical species and thermo-diffusion Darcy–Forchheimer squeezed flow of Jeffrey nanofluid in horizontal channel with viscous dissipation effects

This research communicates the applications of thermos-diffusion effect associated to the squeezing flow of Jeffrey nanofluid due to horizontal channel. The problem presents the applications of inertial effects by following the Darcy–Forchheimer flow. Moreover, the effects of viscous dissipation and activation energy phenomenon has been discussed. The dimensionless attention of problem is retained. The shooting technique is implemented to present the numerical computations. The numerical validation of results is reported. The essential assessment of physical flow parameters is studied. The numerical outcomes are presented for heat and mass transfer phenomenon. It is observed that presence of inertial forces control to velocity flow in the regime. The enhancing contribution of thermal and concentration rate is noted for inertial constant.

A lubricated stagnation point flow of nanofluid with heat and mass transfer phenomenon: Significance to hydraulic systems

The improved thermal association of heat transfer is considerably observed due to interaction of nanoparticles in recent days. The lubrication phenomenon with heat and mass transfer effects plays a key role in the hydraulic systems. In current research, the thermal impact of nanofluid over a lubricated stretching surfaces near a stagnation point analytical has been studied. A thin layer of lubricating fluid with a variable thickness provides lubrication. The inspection of thermophoresis and Brownian motion phenomenon is illustrated via Boungrino model. The analytical finding of refurbished boundary layer ordinary differential equations is obtained by a reliable and proficient technique namely variational iteration method (VIM). The Lagrange Multiplier is a potent tool in proposed technique to reduce the computational work. In addition, a numerical comparison is presented to show the effectiveness of this study. The range of flow parameters is based on theoretical flow assumptions. Physical inspection of involved parameters on velocities, temperatures, concentrations, and other quantities of interest when lubrication is presented. The current results present applications in polymer process, manufacturing systems, heat transfer and hydraulic systems.

Implementation of the moving control volume and filling front concepts in modelling solid-liquid extraction of vegetable oil from porous and non-porous solids in a fixed bed

Solid-liquid extraction (SLE), in which a solute is transferred from a fixed bed of solids with different porosities into a liquid phase, involves solid matrix diffusivity or intra-particle porosity ( ε p ) to reflect the mass transfer resistance within the solid phase and mass transfer coefficients to describe the resistance within the liquid phase. Models that consider intra-particle porosity do not adequately describe the overall mass transfer, especially when the porosity values are low. For such cases, it is common to employ models based on solid matrix diffusivity. However, such models do not describe the non-linear solute concentration profiles commonly encountered in the liquid loading zone of extractors. A new mathematical model based on a control volume that moves along with the liquid phase is proposed to describe the solute concentration within the particle and liquid phases. Such an approach also enables calculation of the transient and local solute concentrations in the loading zone. The model parameter sets were fitted to the experimental results from the porous systems (soybean layer). The global mean deviation (11.6%) between the model and experimental results demonstrates that the proposed model is consistent and can be used to simulate solid-liquid extraction operations for porous and low-porosity solids. • New mathematical method for improved simulation of the solid-liquid extraction. • Description of the mass transfer phenomena for particles with different porosities. • Column loading zone is assumed and treated by three approaches. • Strategies to improve the numerical stability and convergence of the model. • Adjustment and validation with experimental results from vegetable oil extraction.

A multi-scale model for impingement drying of porous slab

Air impingement drying of a planar sheets of porous materials offers advantages of high and controllable heat and mass transfer rates. The governing heat and mass transfer phenomena involve multi-scale physical mechanisms ranging from mesoscopic pore scale to macroscopic jet scale. This work presents a pore-scale heat and mass transfer model of an unsaturated porous material based on statistically self-similar fractal scaling laws of pore structures. Furthermore, the effective transport coefficients are derived and applied to develop a cross-scale mathematical model for hot air impingement drying of a slab made of an unsaturated porous material. The flow and thermal fields of jet impingement and drying characteristics of unsaturated porous material are modeled numerically. The quantitative correlations between the mesoscopic pore structure and macroscopic heat and mass transfer properties are explored. The proposed fractal pore-scale model of porous material and cross-scale mathematical model of jet impingement show good agreement with experimental data. The effects of jet velocity, porosity as well as pore and tortuosity fractal dimensions on drying rate are discussed in detail. The computational results show that the mesoscopic pore structures indicate significant effect on the drying rate during later stage of drying. Results of this study provide useful guidance for efficient design of impingement of porous materials. • Meso-scale heat and mass transfer model of unsaturated porous material is proposed. • Multi-scale model for laminar impingement drying of porous slab is developed. • Impingement drying performance of porous slab is predicted. • Effect of mesoscopic structure on drying kinetics of porous material is explored.

A study on attempt for determination of permeation kinetics of coumarin at lipid bilayer of liposomes by using capillary electrophoresis with moment analysis theory

It was tried to develop a moment analysis method for the determination of lipid membrane permeability. The first absolute and second central moments of elution peaks measured by liposome electrokinetic chromatography (LEKC) are analyzed by using moment equations. As a concrete example, elution peak profiles of coumarin in a LEKC system, in which liposomes consisting of 1-palmitoyl-2-oleoyl-sn‑glycero-3-phosphocholine (POPC) and phosphatidylserine (PS) are used as a pseudo-stationary phase, were analyzed. It seems that lipid membrane permeability of coumarin across the lipid bilayer of POPC/PS liposomes was measured by the moment analysis method because previous permeability measurements using parallel artificial membrane permeability assay (PAMPA) and Caco-2 cells indicated that coumarin is permeable across lipid bilayer. However, it was also pointed out that the moment analysis method with LEKC is not effective for the determination of lipid membrane permeability and that it provides information about adsorption/desorption kinetics at lipid bilayer of liposomes. Therefore, different moment equations were also developed for the determination of adsorption/desorption rate constants of coumarin from the LEKC data. It was demonstrated that permeation rate constants at lipid bilayer or adsorption/desorption rate constants can be determined from the LEKC data on the basis of moment analysis theory for the mass transfer phenomena of coumarin at the lipid bilayer of POPC/PS liposomes. Mass transfer kinetics of solutes at lipid bilayer should be determined under the conditions that liposomes originally be because they are self-assembling and dynamic systems formed through weak interactions between phospholipid monomers. The moment analysis method using LEKC is effective for the experimental determination of the mass transfer rate constants at the lipid bilayer of liposomes because neither immobilization nor chemical modification of liposomes is necessary when LEKC data are measured. It is expected that the results of this study contribute to the dissemination of an opportunity for the determination of permeation rate constants or adsorption/desorption rate constants at the lipid bilayer of liposomes to many researchers because capillary electrophoresis is widespread.

Energy effectiveness analysis of desiccant coated heat exchanger based on numerical method

The conventional air-to-air heat pumps rely heavily on the condensation dehumidification principle to regulate air humidity, thereby severely limiting the system energy efficiency. Significant energy efficiency improvements can be realized by coating high-performing solid desiccants on both evaporator and condenser heat exchangers. Thus far, existing fundamental analysis developed to evaluate energy performance improvement and achieve accurate performance prediction of desiccant coated heat exchangers with two-phase refrigerant (DCHERs) has been impeded by the complex physical phenomena, approximations in the heat/mass transfer paths, and the severe reliance on the use of empirical correlations. Therefore, in this work, a mathematical approach has been judiciously developed based on mass, momentum, energy, and species conservation principles in order to study the flow field distribution within DCHERs and predict their performance. The model is extensively validated with experimental data obtained under various working conditions with discrepancies of ±10 % and ±9 % for outlet air temperature and humidity, respectively. The model provides essential information on local temperature and humidity distributions, and key insights on the transient heat and mass transfer phenomena. Further, a general design guideline for the performance enhancement of DCHERs is established. Key results from the study reveal that the air RH varies within 15 % along the DCHER’s flow channel. Thick desiccant coating, high inlet air relative humidity, and long air-desiccant contact time markedly improve latent energy effectiveness to a maximum of 0.51. Lastly, employing the proposed guideline to design the heat exchanger with optimal tube configurations yields a 23 % enhancement of latent energy effectiveness.

Stability Characteristics of Planar Rivlin–Ericksen Fluid Interface With Mass and Heat Transfer

Abstract The interface of viscous-Rivlin-Ericksen fluids is analyzed through the linear theory of stability analysis when mass and heat is transferring across the interface. The Rivlin-Ericksen fluid lies in the upper region while the lower region of the interface contains viscous fluid. The gravitational acceleration destabilizes the top-heavy arrangement and interface instability is governed by Rayleigh–Taylor instability. The two-dimensional interface is considered, and the viscous potential flow theory is employed to establish the relationship between perturbation's growth and wave number. This relationship is analyzed, and the perturbation's growth is plotted for various flow parameters. A marginal stability condition is obtained, and it is given in terms of heat transport coefficient Λ and wave number. The marginal stability criterion is analyzed using the well-known Newton–Raphson method. The heat and mass transfer phenomenon drives the unstable interface toward stability. It is pointed out that the viscoelastic coefficient λo influences the interface to be stable while the thickness of the viscoelastic fluid makes the interface unstable. Atwood numbers and Weber numbers show destabilizing behavior.

Impact of time-dependent heat and mass transfer phenomenon for magnetized Sutterby nanofluid flow

Due to widespread applications of nanofluid and working as most effective source of energy researchers as well as engineer paid more attention toward nanofluid, moreover nanofluid are preferred as they are environmentally friendly and having extraordinary thermal properties. . In this article, we have investigated the properties of heat and mass transfer mechanisms for incompressible Sutterby nanofluid past over a stretching non-porous surface. The d magnetic strength is incorporated into the flow regime. The effects of Brownian motion and thermophoresis are also incorporated in this work. Moreover, similarity transformations are used to change the coupled PDEs into a set of coupled ODEs and then these ordinary differential equations are solved numerically using an effective numerical technique, namely, bvp4c. For exploring, the effects of physical parameters on the leading coupled ordinary differential equations, we have presented the graphical analysis and discussed in detail. . The dimensionless thermal distribution is greater with Brownian motion, while the opposite behavior is noticed for the concentration field. The analysis further reveals that the unsteadiness parameter is decreasing functions of the velocity and the temperature field.

Pore‐network modelling of combined molecular diffusion and gravity drainage mechanisms in a porous matrix block: The competitive role of driving forces

AbstractA large part of the world's hydrocarbon resources are located in fractured reservoirs, and mass transfer phenomena play a crucial role in enhanced hydrocarbon recovery from these reservoirs. Pore‐network models have been widely used to study kinetic and pore‐scale micro‐mechanisms. Molecular diffusion involves mass transfer and liquid–vapour phase change and can be simulated by a modified invasion percolation model. Despite the existence of separate pore‐scale studies on molecular diffusion and gravity drainage, no articles have been published that evaluate the combined effect of both mechanisms. This study investigates the competitive roles of the two phenomena and the effective factors controlling each mechanism with the aid of pore‐network models. According to the results obtained, gravity drainage and molecular diffusion would have a synergic effect when they are simultaneously active. Although for a single‐component liquid system, there would be a capillary holdup residual saturation in the pure gravity drainage process (between 11% and 14% for the evaluated cases) and a slow and lengthy evaporation in pure molecular diffusion (between 47% and 57% longer for the cases under study), our investigation revealed that when the two mechanisms coexist, a faster process with no residual liquid is expected. Our findings clarify that when the system is strongly gravity dominated, the liquid body remains integrated, gas–liquid contact recedes in a piston‐like manner, and three‐stage liquid desaturation is observed. Furthermore, highly clustered liquid saturation is observed in strongly capillary‐dominated systems, and the liquid desaturation curve in a capillary‐dominated model has two distinguishable stages. The competitive contribution of gravity drainage and molecular diffusion as the main driving forces of liquid extraction from a single‐block model is quantified for the entire period of desaturation. Depending on the dominance of the production mechanisms, the process is either gravity‐assisted molecular diffusion or diffusion‐assisted gravity drainage.