Mass Transfer Phenomena Research Articles

Numerical methods and its application in freezing process

Numerical method is an efficient tool for simulating freezing process. Three types of numerical methods namely finite difference, finite element and finite volume analysis can be used for simulating freezing process in many fruit and vegetable products. To achieve a high quality of product, there are critical parameters that have corresponding effects to microstructure need to be consider in numerical modelling. However, the accuracy of the models can be improved by including several important parameters such as transport phenomena, ice formation and growth, mass and heat transfer coefficients, also properties of products, so that the assumptions used in developing the model can be justified. For further research, it is hoped that this review paper can provide new insights, so that a numerical model could describe not only heat and mass transfer phenomena but also the whole conditions in freezing process and all the critical parameters can be optimized.

Optimization of technological modes of heterogeneous systems at high turbulence

The phenomena of convective heat and mass transfer in turbulent flows, taking into account chemical reactions, are widespread and play an important role in natural phenomena and in various industries. Knowledge of the regularities of such flows is important in the formation of the theory of combustion physics, the development of new physical and chemical technologies, and the solution of problems of thermal power engineering and ecology. In the course of the study, complex combustion processes have been analyzed from the point of view of dependence on the influence of many physical and chemical parameters of the combustion reaction. In the study of phenomena in multiphase systems, the development of the theory of the formation of liquid droplets at high turbulence is of greatest interest. In this paper, the processes of atomization, ignition, and spatial distribution of droplets in heterogeneous two-phase flows have been studied by means of computer simulation methods. These studies were carried out on the basis of current environmental problems, including the problems of air pollution, consisting of harmful toxic metals, sulfuric, nitric acids, carbon oxides, and other harmful substances. The processes of dispersion and combustion of liquid fuels at high turbulence have been studied by using mathematical modeling methods based on the solution of partial differential equations and the optimal technological combustion mode taking into account the formation of carbon dioxide in the combustion chamber has been determined.

Finite Volume Method for a Time-Dependent Convection-Diffusion-Reaction Equation with Small Parameters

Convection, diffusion, and reaction mechanisms are characteristics of transient mass-transfer phenomena that occur in natural and industrial systems. In this article, we contemplate a passive scalar transport governed by the convection-diffusion-reaction (CDR) equation in 2D flow. The efficiency of solving computationally partial differential equations can be illustrated by using a precise numerical method that yields remarkable precision at a low cost. The accuracy and computational efficiency of two second-order finite difference methods were investigated. The results were compared to a finite volume technique, which has a memory advantage and conserves mass, momentum, and energy even on coarse grids. For various diffusion coefficient values, numerical simulation of unsteady CDR equation are also performed. The techniques were examined for consistency and convergence. The effectiveness and accuracy of these approaches for solving CDR equations are demonstrated by simulation results. Efficiency is measured usingL2andL∞, and the estimated results are compared to the corresponding analytical solution.

Bioremediation of Textile Industrial Effluents Using Nutraceutical Industrial Spent: Laboratory-Scale Demonstration of Circular Economy.

This research reports the first-ever study on abundantly available, environmentally friendly, low-cost and ready-for-use Nutraceutical Industrial Cumin Seed Spent (NICUS) as an innovative adsorbent for bioremediation of a bisazo Acid Red 119 (AR119) dye, a probable mutagen from textile industrial effluents (TIEs). The experiment at the laboratory scale is designed to suit the concepts of sustainability and valorisation under the domain of circular economy. The experimental qe value obtained was 96.00 mg g−1. The optimised conditions of parameters are as follows: pH of 2; adsorption time, 210 min; adsorbent dosage, 0.300 g L−1; particle size, 175 µM; initial dye concentration, 950 mg L−1; orbital shaking, 165 rpm and temperature, 50 °C, producing an impressive value of 748 mg of dye adsorbing on 1 g of dry NICUS. The adsorption capacity of NICUS obtained from the quadratic model developed for process optimisation gave values of 748 mg g−1. As a prelude to commercialisation, five variables that affect the adsorption process were experimentally studied. For the feasibility and efficiency of the process, a two-level fractional factorial experimental design (FFED) was applied to identify variables that influence the adsorption capacity of NICUS. The identified variables were applied to scale experiments by three orders. Nine isotherm models were used to analyse the adsorption equilibrium data. The Vieth–Sladek adsorption isotherm model was found to be the best fit. The pseudo-second-order reaction was the appropriate mechanism for the overall rate of the adsorption process. Mechanistic studies related to mass transfer phenomena were more likely to be dominant over the diffusion process. Techniques such as SEM, FTIR and CHN analysis were used to characterise NICUS. The dye-adsorbed NICUS obtained as “sludge” was used as a reinforcing material for the fabrication of composites using plastic waste. The physicomechanical and chemical properties of thermoplastic and thermoset composite using dye-adsorbed NICUS were evaluated and compared with NICUS composites. Prospects of integrating Small and Medium Enterprises (SMEs) into the circular economy of Nutraceutical Industrial Spent (NIS) are discussed.

Numerical investigation of triangular bluff bodies size effect on heat and mass transfer phenomena: internal flow

Numerical investigation of triangular bluff bodies size effect on heat and mass transfer phenomena: internal flow

Characterisation and modelling of water wicking and evaporation in capillary porous media for passive and energy-efficient applications

Passive devices based on water wicking and evaporation offer a robust, cheap, off-grid, energy-efficient and sustainable alternative to a wide variety of applications, ranging from personal thermal management to water treatment, from filtration to sustainable cooling technologies. Among the available, highly-engineered materials currently employed for these purposes, polyethylene-based fabrics offer a promising alternative thanks to the precise control of their fabrication parameters, their light-weight, thermal and mechanical properties, chemical stability and sustainability. As such, both woven and non-woven fabrics are commonly used in capillary-fed devices, and their wicking properties have been extensively modelled relying on analytical equations. However, a comprehensive and flexible modelling framework able to investigate and couple all the heat and mass transfer phenomena regulating the water dynamics in complex 2-D and 3-D porous components is currently missing. This work presents a comprehensive theoretical model aimed to investigate the wetting and drying performance of hydrophilic porous materials depending on their structural properties and on the external environmental conditions. The model is first validated against experiments (R2=0.99 for the wicking model; errors lower than 14% and 1% for the evaporation and radiative models, respectively), then employed in three application cases: the characterisation of the capillary properties of a novel textile; the assessment of the thermal performance of a known material for personal thermal management when used in different conditions; the model-assisted design of a porous hydrophilic component of passive devices for water desalination. The obtained results showed a deep interconnection between the different heat and mass transfer mechanisms, the porous structure and external working conditions. Thus, modelling their non-linear behaviour plays a crucial role in determining the optimal material characteristics to maximise the performance of porous materials for passive devices for the energy and water sector.

Method of heat and mass transfer calculation of cooling technical water process at CHP plant when cooling pond with spray devices is operated

The generation of electrical energy at thermal and nuclear power plants is associated with outward heat transmission of large amount. Cooling devices (cooling towers, spray pools, reservoirs) are used for its utilization. The increase of the efficiency of the cooling capacity of this equipment in the circulating water supply system of the CHP plant is occurred due to a decrease of temperatures that meet the optimal technical and economic performance of the facility. The studies of I.I. Makarova, V.A. Gladkova, B.S. Farfarovsky, Z.K. Maimekova, S.A. Suprun are devoted to these issues. The aim of the study is to develop a methodology to calculate the process of cooling technical water to create an operating temperature mode of the equipment during condensation of the waste heat of steam turbines and to minimize the amount of additional water from the Tom River in the warm season. To evaluate the operation of spray devices the authors have used experimental data obtained during the survey of the cooling pond of the West Siberian CHP plant in Novokuznetsk city and methods of physical modeling of heat and mass transfer. To increase the efficiency of technical water cooling at the CHP plant, it is proposed to install spray devices in addition to the existing cooling pond. A method has been developed to calculate the process of water cooling in spray devices during collaboration with a cooling pond. The method is based on the calculation of the optimal water temperature at the intake point in accordance with the operating parameters of turbine generator condensers. The method differs from the existing ones as it considers the influence of heat transfer and mass transfer phenomena in the boundary layer near the surface of dispersed drops water. The experimental and calculated results confirm that the use of spray devices in the cooling pond reduces the amount of additional water taken from the Tom River compared to its limit flow by almost 10 times at the established temperature difference during the condensation of exhaust steam in the summer period of the year. The method to calculate the cooling of technical water in a cooling pond with spray devices is recommended for implementation at the West Siberian CHP plant in Novokuznetsk city.

Effect of in-situ ultrasonic impact treatment on flow and solidification behavior of laser metal deposition: By finite element simulation

Due to the special thermal history of laser metal deposition (LMD), the microstructure of deposition layer is mainly columnar crystal which has a negative effect on the mechanical properties of the additive manufactured parts. In-situ ultrasonic impact treatment is an assistive technology, which can refine grain size, reduce residual stress and improve fatigue strength effectively. Finite element simulation is an important method to study the heat and mass transfer phenomenon in molten pool, which can save time and materials. However, few scholars have studied the influence of ultrasonic impact treatment on molten pool by finite element simulation. The effect of acoustic streaming in the molten pool caused by ultrasonic impact treatment on the flow behavior, heat transfer behavior and solidification conditions at the solidification boundary of the molten pool have been studied by finite element simulation in this paper. The results show that ultrasonic impact treatment can promote the maximum velocity in the molten pool, reduce the temperature of the molten pool and change the shape of the molten pool from round to oval. Besides during the solidification process, the temperature gradient decreases first and then increases, and the solidification rate increases first and then decreases with increasing ultrasonic power. Ultrasonic impact treatment can improve the microstructure of the deposition layer during solidification process by increasing cooling rate. This finite element simulation research can provide guidance for process development, structure control and property improvement for in-situ ultrasonic impact treatment assisted laser metal deposition.

Study of Onboard Hydrogen-Rich Gas Generation for Gasoline Engine by Gasoline Steam Reforming with Exhaust Gas Energy Recovery

This study was to investigate the potential for hydrogen-rich gas generation, the clean fuel, for gasoline engines by onboard gasoline steam reforming with exhaust gas energy recovery. The study was conducted on a motorcycle gasoline engine of 100 cm3 swept volume in a laboratory combined with modeling. The modeling study was to determine the optimal feedstock conditions for high generated hydrogen yield while the experiment was to validate and confirm the solution. The study accounted for all the aspects of major chemical reactions and heat and mass transfer phenomena in the reformer. A computer simulation code has been developed for the study. The results showed that by taking advantage of exhaust energy, the optimal operating conditions of the reformer for high hydrogen yield were under engine full load with inlet fuel flowrate of 110 g/h and mass water to fuel ratio of 3.5:1. Under these conditions, gasoline conversion of up to 80% and H2 yield of 30.8 g/h was achieved.

Chemo-Enzymatic Production of 4-Nitrophenyl-2-acetamido-2-deoxy-α-D-galactopyranoside Using Immobilized β-N-Acetylhexosaminidase

α-Nitrophenyl derivatives of glycosides are convenient substrates used to detect and characterize α-N-acetylgalactosaminidase. A new procedure combining chemical and biocatalytic steps was developed to prepare 4-nitrophenyl-2-acetamido-2-deoxy-α-D-galactopyranoside (4NP-α-GalNAc). The α-anomer was prepared through chemical synthesis of an anomeric mixture followed by selective removal of the β-anomer using specific enzymatic hydrolysis. Fungal β-N-acetylhexosaminidase (Hex) from Penicillium oxalicum CCF 1959 served this purpose owing to its high chemo-and regioselectivity towards the β-anomeric N-acetylgalactosamine (GalNAc) derivative. The kinetic measurements of the hydrolytic reaction showed that the enzyme was not inhibited by the substrate or reaction products. The immobilization of Hex in lens-shaped polyvinyl alcohol hydrogel capsules provided a biocatalyst with very good storage and operational stability. The immobilized Hex retained 97% of the initial activity after ten repeated uses and 90% of the initial activity after 18 months of storage at 4 °C. Immobilization inactivated 65% of the enzyme activity. However, the effectiveness factor and kinetic and mass transfer phenomena approached unity indicating negligible mass transfer limitations.

Kinetic Modeling of Heat and Mass Transfer During Deep Fat Frying of Churro

The effect of deep fat frying temperatures, ranging from 160 to 190 oC, on frying parameters including the heat transfer coefficient (he), mass transfer coefficient (ke) and effective moisture diffusivity (De) were investigated during deep fat frying of churro that is fried dough pastry. Therefore experimental studies were conducted for both heat and mass transfer phenomena and mathematical model was developed for simultaneous transfer by using Newman technique for churro actual geometry (3-D cylindrical shape). Fourier’s and Fick’s laws were applied for computation of coefficients of heat and mass transfer. The he coefficients were 437.360-93.535 W/m2K in the temperatures range of 160 to 190 oC. However, the value of ke and De increased by an increase in oil temperature during frying. The maximum values were determined as 17.36 x10-5 m/s and 2.48 x10-5 m2/s at 190 oC for ke and De, respectively. Model and experimental data had good agreement and the transfer coefficients followed the first order kinetic model with high R2 and low RMSE values. There was found an Arrhenius equation between the effective moisture diffusivity and deep fat frying temperature, so the value of activation energy was calculated as 63.546 kj/mol.

Depolymerization of Waste Plastic Using Bubble Column for Nano Alumina Blended Coating

In this study, we aimed to figure out how the depolymerization of polyethylene terephthalate produces monomers, dimers, trimers, and other oligomers of bis (2-hydroxyethyl) terephthalate. Polymerization was achieved in a bubble column reactor with 0.05 wt% 40–50 nm magnesium oxide nanoparticle as a catalyst. A bubble column reactor was used to perform the recycling process at the boiling point of ethylene glycol and atmospheric pressure. Depolymerized polyethylene terephthalate (DPET) was mixed with poly(methyl methacrylate) and reinforced with 1% Nano Al2O3. The nanoparticles acted as a composite coating in low carbon steel protection. Adhesion strength and mechanical and structural properties were investigated for the composite, and the average coating thickness was 28.39 µm. The results showed that the hardness and adhesion forces between the substrate and composite coating increased with an increase in the amounts of DPET and nano-Al2O3 per polymer resin. On the other hand, the thermal conductivity of the composite coating decreased with the addition of DPET because of an increase in the end chain movement in the composite coating induced by the retardant and an increase in cross-linking force. Furthermore, the bubble column demonstrated outstanding heat and mass transfer phenomena that reduced the reaction time to just 40 min for complete depolymerzation and also reduced energy consumption.

3D CFD study of hydrodynamics and mass transfer phenomena for spiral wound membrane submerged-type feed spacer with different node geometries and sizes

Modification of the spacer geometry is a promising approach to increase the efficiency of reverse osmosis (RO) spiral wound membrane modules. Column nodes and spherical nodes are considered in this three-dimensional computational fluid dynamic (CFD) study to evaluate the hydrodynamic and mass transfer performance of submerged spacers with different node geometries and sizes. Small-scale CFD analysis results reveal that the column node has better mass transfer performance than the spherical node geometry because column nodes divert more flow to the filaments, leading to higher local velocity at the region between the filament and wall. Furthermore, when the dimensionless node diameter ratio of the column nodes increases from 0.3 to 1.2, Sherwood number and wall shear increase by 25% and 8% respectively at the expense of higher global friction factor (44%). A sea water RO full-scale analysis revealed that column node spacers yield higher average flux than spherical nodes and conventional spacers at high feed inlet velocity (> 0.1 m/s), because the mixing effects by the spacer that improve mass transfer are more prominent.

Simulation of conjugate mass transfer in multiphase flow: A new unified approach based on the phase field method

Conjugate mass transfer phenomena are commonly found in industries and nature. It raises a serious challenge for numerical research, because at interfaces not only the continuity of mass flux but also the concentration jump (i.e. Henry's law) must be guaranteed. A complicated interface will further increase the complexity of numerical research of conjugate mass transfer. The phase field method has an intrinsic advantage over the other available numerical methods to model complicated interfaces, but so far there is no efforts to investigate interphase mass transfer with the aid of phase field method. The challenge is to design an appropriate governing equation for concentration field, which can be coupled with the phase field method and meanwhile can describe conjugate mass transfer in a unified manner. In this study, a new governing equation for concentration field is proposed to address the challenge. A number of benchmark test cases are employed to validate the present approach. The excellent agreement of the present numerical results with the analytical solutions and published data can demonstrate the applicability of the present approach for simulating conjugate mass transfer not only with a flat stationary interface but also with a moving/curved interface.

Numerical and experimental study of heterogeneous reactions involving carbonaceous compounds in clay brick firing

Clay bricks have been used as a construction material by humans since thousands of years. Modern brick making however is challenged by the still energy-intensive production, coming together with considerable amounts of greenhouse gas emissions and consequently climate impact. Therefore, the physicochemical fundamentals of the brick firing process should be studied, in order to provide insight to possible technological changes. The present study deals with the heterogeneous chemical reactions, which occur in the thermo-chemical conversion of a clay brick mixture rich in carbonates and blended with organic additives. An integrated solution of the actual mass and heat transfer phenomena resulting from the reactions of carbon-related compounds inside a porous brick body under heat exposure is provided. The partial and global mass balances as well as the heat balance are represented by the relevant differential equations, which were solved using a finite differences method. The chemical kinetics of the carbonates’ calcination and the oxidation of the added organic substance (wood particles) were obtained by thermogravimetric analysis and the results deployed for parameterizing the global reaction model. An accurate description of the effective diffusion coefficients by means of the mean transport-pore model was implemented to the global reaction model. Combustion experiments with cylinder-shaped clay specimens conducted in a fluidized bed lab reactor were used for evaluation of the model. After simple adaptations of the parameterization, the model predictions showed good agreement with the experimental data. Parameter sensitivity analyses and various model tests demonstrate the practical suitability of the presented reaction model for the thermo-chemical process of brick firing.

Impact of liquid coolant subcooling on boiling heat transfer and dryout in heat-generating porous media

The present article discusses the impact of liquid coolant subcooling on multiphase fluid flow and boiling heat transfer in porous media with internal heat generation. Although extremely relevant and important, only limited studies are available in the open literature on the effects of coolant subcooling in heat-generating porous media and hence, this requires a detailed analysis. The present analysis is carried out using a validated computational model of multiphase fluid flow through clear fluid and porous media considering the relevant fluid transport, heat transfer and mass transfer phenomena. Results suggest that the qualitative nature of boiling heat transfer from the heat-generating porous body, with subcooled coolants, remain similar to that observed with a saturated coolant. Quantitative differences are, however, observed as a result of solid–liquid convective heat transfer, and competing mechanisms of boiling and condensation heat transfer, when subcooled liquid coolant is present. It is observed that a substantially larger heating power density is required - as coolant subcooling is increased - for achieving the same temperature rise in the porous body. Dryout power density at different coolant subcooling is also observed to follow a similar trend. The thermal energy removal limit is, hence, observed to be substantially enhanced in presence of subcooled coolants. Further, the dryout region within the porous body is observed to gradually shift towards its interior as the coolant subcooling is increased.

Influence of enzyme immobilization and skin-sensor interface on non-invasive glucose determination from interstitial fluid obtained by magnetohydrodynamic extraction

We integrated a magnetohydrodynamic fluid extractor with an amperometric glucose biosensor to develop a wearable device for non-invasive glucose monitoring. Reproducible fluid extraction through the skin and efficient transport of the extracted fluid to the biosensor surface are prerequisites for non-invasive glucose monitoring. We optimized the enzyme immobilization and the interface layer between the sensing device and the skin. The monitoring device was evaluated by extracting fluid through porcine skin followed by glucose detection at the biosensor. The biosensor featured a screen-printed layer of Prussian Blue that was coated with a layer containing glucose oxidase. Both physical entrapment of glucose oxidase in chitosan and tethering of glucose oxidase to electrospun nanofibers were evaluated. Binding of glucose oxidase to nanofibers under mild conditions provided a stable biosensor with analytical performance suitable for accurate detection of micromolar concentrations of glucose. Hydrogels of varying thickness (95–2000 μm) as well as a thin (30 μm) nanofibrous polycaprolactone mat were studied as an interface layer between the biosensor and the skin. The effect of mass transfer phenomena at the biosensor-skin interface on the analytical performance of the biosensor was evaluated. The sensing device detected glucose extracted through porcine skin with an apparent (overall) sensitivity of −0.8 mA/(M·cm2), compared to a sensitivity of −17 mA/(M·cm2) for measurement in solution. The amperometric response of the biosensor correlated with the glucose concentration in the fluid that had been extracted through porcine skin with the magnetohydrodynamic technique.

A numerical approach to interpret melting and activation energy phenomenon on the magnetized transient flow of Prandtl–Eyring fluid with the application of Cattaneo–Christov theory

The current study explores the Impact of activation energy and melting heat transfer on unsteady Prandtl–Eyring model with variable thermal conductivity induced by a stretched cylinder. The Cattaneo–Christov double diffusion theory is used to study heat and mass transfer phenomena. The foremost coupled partial differential equations (PDEs) of the time-dependent Prandtl–Eyring model is transformed to ordinary ones using appropriate local similarity variables. The deduced system is numerically solved using the shooting iterative technique. The characteristics of key flow parameters against fluid concentration, temperature, velocity, skin friction, Sherwood and local Nusselt numbers are examined graphically with justified physical consequences. The comparison with the previously published work showed a fabulous agreement. This investigation presented that the velocity and concentration of fluid are increased by enhancing melting and curvature parameters, while the fluid temperature is diminished due to the impacts of melting and curvature parameters. By raising reaction rate constant, melting, thermal relaxation time, and temperature difference parameters, the fluid temperature is enhanced while the fluid temperature declines with thermal conductivity, activation energy, and unsteadiness parameters. Furthermore, the unsteadiness and activation energy parameters cause a rise in the concentration of a fluid.

Influence of temperature, ultrasound, and variety on moisture diffusivity and thermodynamic properties of some durum wheat varieties during hydration

This study covers the effect of temperature, ultrasound, and variety on moisture diffusivity and thermodynamic properties of durum wheat varieties during hydration. The process was performed at hydration temperatures of 25, 35, 45, and 55°C during conventional and ultrasound-assisted soaking. The Fick’s diffusion model fitted the experimental data satisfactorily with average coefficient of determination of 0.9946, root mean square error (%, d.b) of 0.0296, Chi-square of 0.0013, and relative mean error (%) of 0.0205, respectively. Deff of wheat varieties during hydration process increased with the ultrasound treatment and temperature increase. Activation energy of wheat varieties decreased with the ultrasound (40 kHz, 200 W) treatment. Increase in Gibbs free energy and negative values of enthalpy and entropy changes with increasing temperature and ultrasonication process confirming the effect of temperature and ultrasound on Deff of wheat varieties during hydration process. Novelty impact statement The results of this investigation can assist wheat products industry in understanding heat and mass transfer phenomena during ultrasound-assisted hydration process of different wheat varieties in tempering, cooking, milling, fermentation, formulation of meals, and storage processes. The results of this study can also be useful in optimizing ultrasound-assisted hydration process and improving the thermodynamic properties of different wheat varieties. New derived generalized hydration equations can be useful for temperature and time-dependent moisture content detection during ultrasound-assisted and conventional hydration processes of wheat varieties.

Numerical Simulation of the Cleaning Performance of a Venturi Scrubber

Industrial applications need to use different systems for the problem of gas cleaning. A lot of processes have been developed, such as the use of a venturi for gas cleaning and pollution reduction. Additionally, several studies have been developed especially in terms of pressure drop because it is one of the main parameters to determine its efficiency. While the phenomenon of mass transfer in a venturi scrubber has not found much attention, in the present study, a mass transfer two-dimensional simulation is developed for gasification gas cleaning through a venturi scrubber with boundary conditions represented in air inlet velocities of 10, 15, and 20 m/s and water inlet mass flow of 0.02, 0.04 and 0.06 kg/s. In this work, Navier–Stokes equations are solved numerically and the mass transfer technique is treated by the volume of fluid (VOF) model, using CFD software. The obtained results were analyzed by presenting the mass fraction, velocity and pressure contours, and profiles. The probability density function (PDF) of mass transfer is studied too, showing how the removal efficiency of the venturi scrubber increases with a decrease in the liquid flow rate and an increase in the gas velocity. Therefore, the results show that the proposed venturi has the best mass transfer performance with a PDF that reaches 97.6 for velocity liquid of 20 m/s and the removal efficiency showed higher values at low liquid flow rates.