Reaction Rate Parameters Research Articles

Influence of couple stress, radiation, and activation energy on MHD flow and entropy generation in Maxwell hybrid nanofluid flow over a flat plate

Countless engineering applications rely on heat and mass transportation technologies. Limitations in thermal conductivity and mass diffusivity are common in conventional fluids. Nanofluids, which are essentially base fluids with nanoparticles suspended in them, have superior thermal characteristics than base fluids without the nanoparticles. Maxwell hybrid nanofluids have the potential to improve mass and heat transport even further by combining the characteristics of two different types of nanoparticles. The magnetohydrodynamic (MHD) flow and heat transmission properties of a Maxwell hybrid nanofluid through a flat plate are investigated in this work. The novelty of this research lies in its exploration of the combined impressions of couple stress and activation energy on the flow behaviour. The equations governing the problem undergo transformation and are handled by means of the bvp4c solver. The vital discoveries disclose that the nanoparticle concentration and magnetic field strength act as opposing forces to fluid velocity. And also, it is detected that the friction coefficient rises by 2.68% as the value of volume fraction of copper nanoparticles ranges from 0 to 0.105. It is found that there is a decrement of 29.7% in the heat transmission rate when the values of Eckert number lie between 0 and 0.6. It is observed that the reaction rate and activation energy parameters play opposite roles against fluid concentration. It is discovered that the entropy generation increases with factors that enhance friction and heat dissipation (Maxwell and Brinkman parameters). The results show that the Sherwood number drops 4.4% when the activation energy parameter is set to values between 0 and 3.

Optimization control strategy for diesel urea-selective catalytic reduction (SCR) urea injection based on the interior point method (IP) + higher order SCR model

In order to ensure that the NOx and NH3 emissions of diesel engines comply with the Euro VII emission standards, this paper optimizes the urea injection using a SCR model combined with the interior point method. First, the equations of the higher-order SCR model were simplified by the variable substitution method and the line method and solved by the backward difference formula to improve computational accuracy. The Levenberg-Marquardt algorithm was used to calibrate the chemical reaction rate parameters to optimize model performance. Second, an optimization cost function was designed to optimize the upstream NH3 concentration in combination with the interior point method and the higher-order SCR model to meet the requirements of Euro VII emission standards. Third, the model effect was verified by performing WHTC hot-start testing on an engine complying with the National VI emission standard. The results show that the average error between the measured NOx concentration and the calculated is 1.49 ppm, which verifies the high accuracy of the model. Finally, the effects of the interior point method, NSGA-II, and MOPSO algorithms in optimizing the upstream NH3 concentration were compared. The results showed that the interior point method outperformed the other algorithms in terms of optimization time and effect, with an optimization time of 149 s, a NOx conversion rate of 97.36 %, and an average downstream NH3 concentration of 4.65 ppm. This achieved a high NOx conversion rate and low NH3 slip in accordance with the requirements of the Euro VII regulation.

Entropy generation minimization and activation energy in magneto-thermo-solutal stratified Ellis hybrid nanofluid flow through a stretching stenotic artery: Insights into cardiovascular disease

This article explores the impact of binary chemical reactions with activation energy on the flow of magnetized mono and hybrid nanofluids within a porous artery under the effects of viscous dissipation, nonlinear thermal radiation, and Joule heating. The main novelty of this study lies in considering a non-Newtonian Ellis fluid model of blood through a stretching stenotic artery consisting of gold (Au) and silver (Ag) nanoparticles. Additionally, velocity slip, convective temperature, and concentration boundary conditions are applied at the arterial surface. The proposed model compares the performance of Ag/Blood nanofluid and Au-Ag/Blood hybrid nanofluid models. The governing equations are solved using the bvp4c built-in solver in MATLAB, which employs advanced numerical techniques and algorithms tailored for BVPs, ensuring quicker convergence with minor errors and accurate solutions. Graphs are plotted for concentration, temperature, velocity, entropy minimization, skin friction coefficient, Nusselt number, and Sherwood number for various physical parameters. The results show that with increased nonlinear thermal radiation (0.1≤Nr≤2.0), thermal Biot number (0.1≤Bi1≤0.3), and Eckert number (0.01≤Ec≤0.2), the thermal distribution profile exhibits a rising trend. In contrast, with increasing fluctuations in the chemical reaction rate parameter (0.1≤Rc≤0.3) and Schmidt number (1.0≤Sc≤3.0), the concentration distribution profile exhibits a decreasing trend. In terms of mass and heat transfer efficiency, the Au-Ag/Blood hybrid nanofluid flow outperforms the Ag/Blood nanofluid model. More entropy is observed for Au-Ag/Blood compared to Ag/Blood in the stenotic artery. Heat energy may be created by targeting the injured area and avoiding harm to nearby tissues. Localized heating can widen arteries and increase blood flow to the affected locations, potentially aiding cardiovascular health management and personalized therapy. This study has various implications for the design of drug delivery systems, biophysical models, innovative materials, and our knowledge of fluid dynamics and heat transfer. However, nanofluid/hybrid nanofluid stability is challenging for current researchers since this modeled flow can be considered over a shrinking artery or in the trihybrid model in future studies.

Effects of Arrhenius activation energy and melting heat transfer on Carreau fluid through a stretching sheet

ABSTRACT This article investigates the effect of activation energy on Carreau fluid flow in the presence of variable thermal conductivity, inclined magnetic field, melting heat transfer, and Soret and Dufour phenomena. A set of suitable similarity transformations is applied for transforming the governing partial differential equations (PDEs) considered for the physical phenomena into non-linear ordinary differential equations (ODEs). We obtained the results by solving the non-linear ODEs numerically which describe the behavior of the velocity, temperature, and concentration profiles of the fluid against the governing parameters and illustrated these graphically. The velocity distribution decreases for angle of inclination while it is increasing against higher melting parameter. The temperature distribution enhances with higher modified Dufour parameter and Prandtl number while it declines for thermal conductivity, activation energy, and melting parameters. The concentration distribution increases for melting parameter, Soret number, and activation energy parameter while decreasing for temperature difference parameter, Schmidt number, and reaction rate parameter. Skin friction, Nusselt and Sherwood numbers are evaluated numerically against the various governing parameters. Accuracy of the present work is illustrated and established through comparison carried out for skin friction versus magnetic parameter with existing results in the literature.

Numerical illustration using finite difference method for the transient flow through porous microchannel and statistical interpretation of entropy using response surface methodology

The current article discloses the influence of the hyperbolic tangent nanofluid on time dependent flow through a microchannel when a magnetic field is applied. The porous medium was incorporated using the Darcy–Forchheimer model. The chemical reaction is explained by Arrhenius activation energy. Temperature is determined by convective boundary conditions. The irreversibility occurring in the flow is analyzed. The modeled problem gives rise to partial differential equations, which are computed by finite difference method. Response surface methodology, an optimization technique, is used to attain the optimal conditions for entropy generated for the flow of fluid. Results of the analysis reveal that concentration decreases with the rise in reaction rate parameter and increases with activation energy parameter. Prandtl and Eckert numbers, with their increase, enhance entropy, and fluid friction irreversibility is at its highest. Perfect co-relation is attained for the model by the response surface methodology, with a co-relation coefficient of 100 %. The Weissenberg number is highly sensitive to change in the present modeling, followed by Darcy and Reynolds numbers. The Reynolds number and Darcy number show positive sensitivity, while the Weissenberg number shows negative sensitivity to the entropy generated.

Neural network algorithms of a curved riga sensor in a ternary hybrid nanofluid with chemical reaction and Arrhenius kinetics

To improve the thermal management systems in industrial operations, there is a need for the prediction and complexity of advanced fluid motion across various physical conditions on different geometries. Further, ternary nanofluid flow across curved Riga surfaces plays a significant role in thermal management systems, chemical industries, thermal management systems, biomedical, environmental engineering, and more. Based on the above importance the current study focuses artificial neural network (ANN) model on the ternary nanofluid flow over a curved Riga surface in the presence of chemical reaction and activation energy. Proper assumptions and boundary layer approximation were used to develop the model. Using appropriate similarity variables, the governing equations are further simplified to ordinary differential equations (ODEs). Runge Kutta Fehlberg's 4th-5th order and shooting process are applied to solve the simplified equations. The primary objective is to improve the construction and optimization of thermal administration systems and other manufacturing procedures by gaining a deeper knowledge of the fluid motion and characteristics of heat transfer involved. Graphs are used to provide additional context for the important dimensionless constraints. The obtained data was utilized to train the ANN model, which was then verified towards numerical values of important engineering coefficients. The results reveal that the addition of solid volume fraction will enhance the thermal profile while declining the concentration profile. The reaction rate parameter will decline the concentration, and a reverse trend is seen for the activation energy parameter. The constructed model exhibits an outstanding degree of precision throughout the procedure, spanning all phases of the research.

Simplification and verification of chemical reaction mechanism of RP-3 aviation kerosene

To reveal the combustion and explosion characteristics of RP-3 aviation kerosene, a three-step simplified mechanism involving CO-CO2, H2-H2O equilibrium was constructed. Using a general program based on Cantera and genetic algorithms, the reaction rate parameters were optimized under given conditions, and a relationship between reaction rate parameters and fuel equivalence ratio was developed. The optimized mechanism was compared with multiple flame parameters under multiple operating conditions of RP-3 aviation kerosene. The results showed that the laminar flame speed and adiabatic flame temperature of the three-step simplified mechanism were in good agreement with the experimental data of RP-3 aviation kerosene within the temperature range of 300 ∼ 600 K and pressure range of 1–5 atm, with an error of less than 10 %. The optimized mechanism corrected using a correction function is in good agreement with experimental and numerical results under multiple conditions, verifying the rationality of the simplified program and the accuracy of the three-step simplified mechanism. For practical engineering issues, RP-3 aviation kerosene explosion experiments were conducted, and the pressure and flame data were analyzed and compared. The results indicated that the three-step simplified mechanism had satisfactory calculation time scales and numerical simulation feasibility.

Impact of chemical reaction on the Cattaneo–Christov heat flux model for viscoelastic flow over an exponentially stretching sheet

In this article, the numerical solutions for the heat transfer flow of an upper-convected Maxwell fluid across an exponentially stretched sheet with a chemical reaction on the Cattaneo–Christov heat flux model have been investigated. Using similarity transformation, the controlling system of nonlinear partial differential equations was transformed into a system of ordinary differential equations. The resulting converted equations were solved numerically by a successive linearization method with the help of MATLAB software. A graphic representation was created to analyze the physical insights of the relevant flow characteristics. The findings were presented in the form of velocity, temperature, and concentration profiles. As the relaxation time parameter varied, the local Nusselt number increased. The thermal relaxation time was shown to have an inverse relationship with fluid temperature. Furthermore, the concentration boundary layer becomes thinner as the levels of the reaction rate parameter increase. The results of this model can be applicable in biological fluids and industrial situations. Excellent agreement exists between the analysis's findings and those of the previous studies.

Turbulent and non-turbulent analysis of thermomagnetic convection and heat transfer of darcian radiative nanofluid flow across inclined stretching surface in microgravity environment

Turbulent and non-turbulent analysis of thermomagnetic convection, heating rate and mass transport of Darcian radiating nanofluid flow through porous slanted sheet is the aim of present study. Influence of microgravity is more useful for the movement of thermophoresis nanoparticles with maximum temperature and density. Joule heating, porous medium, magnetic field and thermal radiations are incorporated for the performance of thermal convection. Governing equations are reduced in dimensionless form. Oscillatory stokes conditions are applied to separate the steady, real and imaginary equations. Finite difference, Primitive transformation, and Gaussian elimination techniques are applied for numerical outputs. For asymptotic results, the appropriate range of parameters such as 0.1≤JH≤15.0, 0.1≤Pr≤12.0, 0.1≤Rd≤25.0, 0.0≤λT≤5.0, 0.1≤NT≤1.0, 0.1≤Fr≥6.0, and 0.1≤δ≤1.0 is utilized. Main novelty of work is to examine the steady state and oscillatory behavior of friction-rate, heat/mass transport over slanted two-angles π/6 and π/4. Maximum amplitude in fluid velocity is observed by increasing radiations and buoyant forces. Temperature distribution and nanomaterial concentrations enhance as Joule-heating and Prandtl number increases under microgravity region. Amplitude and oscillation of heat and mass rate is increased as reaction rate, Joule heating and Forchheimer parameter increases. Enhancing behavior of energy transport is observed for maximum choice of Prandtl index with small magnetic effects. It is depicted that high rate of oscillating frequency in heat transmission is detected with maximum radiation effects.

Integrated Effects of Site Hydrology and Vegetation on Exchange Fluxes and Nutrient Cycling at a Coastal Terrestrial‐Aquatic Interface

AbstractThe complex interactions among soil, vegetation, and site hydrologic conditions driven by precipitation and tidal cycles control the biogeochemical transformations and bi‐directional exchange of carbon and nutrients across the terrestrial–aquatic interfaces (TAIs) in coastal regions. This study uses a highly mechanistic model, Advanced Terrestrial Simulator (ATS)‐PFLOTRAN, to explore how these interactions affect exchanges of materials and carbon and nitrogen cycling. We used a transect in the Chesapeake Bay region that spans zones of open water, coastal wetland, transition, and upland forest. We designed several simulation scenarios to parse the effects of the individual controlling factors and the sensitivity of carbon cycling to reaction rate parameters derived from laboratory experiments. Our simulations reveal an active zone for carbon cycling under the transition zones between the wetland and the upland. Evapotranspiration is found to enhance the exchange fluxes between the surface and subsurface domains, resulting in a higher dissolved oxygen concentration in the TAIs. The transport of organic carbon derived from plant leaves and roots provide an additional source of organic carbon needed for the aerobic respiration and denitrification processes in the TAIs. The variability in reaction rate parameters associated with microbial activities is also found to play a dominant role in controlling the heterogeneity and dynamics of the simulated redox conditions. This modeling‐focused exploratory study enabled us to better understand the complex interactions among soil, water and microbes that govern the hydro‐biogeochemical processes at the TAIs, which is an important step toward representing coastal ecosystems in larger‐scale Earth system models.

Cattaneo-Christov Heat Flux Model for Bio-Convective Radiative Eyring-Powell Nanofluid with Viscous-Ohmic Dissipation and Magnetic Dipole Impacts

In this work we studied the solutions of the bio-convected Eyring-Powell nanofluid involving gyrotactic micro-organisms in the presence of viscous-ohmic dissipation, double diffusion, and magnetic field over a stretched sheet under the impacts of nonlinear radiation and Arrhenius activation energy. The magneto-nanoparticles suspension in microorganisms are beneficial in nanofluid stability. Also, they have number of applications in nanosciences, biotech, pharmaceuticals, and mechanical development. The nonlinear coupled PDEs are transformed into ODEs by taking a suitable set of similarity transformations and then computationally solved with MATLAB’s bvp4c and RK4-Shooting technique. The skin friction coefficient, Nusselt number, and Sherwood number are represented in tabular form. The mass and heat transmission rate improve in the presence of gyrotactic microorganisms. The temperature as well as concentration of Eyring-Powell Nanofluid get decreased by accelerating the significant mass and thermal stratification. The concentration profile Φ(η) depreciate for higher Chemical reaction rate (σ), Schmidt number (Sc), and temperature difference (δ1) parameters but rises upon increasing values of Activation energy (Ea). Also, the microorganism concentration difference parameter (β1), bioconvection Lewis number Lb and Peclet number Pe are opposing the motile microorganism density profile.

Impact of Darcy-Forchheimer for the flow analysis of radiated tangent hyperbolic fluid with viscous dissipation and activation energy

In the present analysis, tangent hyperbolic fluid is assumed to be flowing over a stretching cylinder. The thermophysical characteristics of fluids are assumed to be variable. The thermal and solutal rates are investigated by using viscous dissipation, activation energy, and thermal radiation. The governing equations occur in the form of partial differential equations, and then these equations are transformed into ordinary differential equations by using similarity transformations. Then, by using the BVP4C method, we obtain the numerical solution to the equations. The impacts of the involved parameters, such as Prandtl, Weissenberg, Schmidt, Eckert number, viscosity coefficient, and thermal radiation parameters, are presented through the graphs. The velocity profile decreases due to the power law index, Weissenberg number, and temperature-dependent viscosity. However, it increases due to the Darcy-Forchheimer number and curvature parameter. The temperature distribution rises with the Eckert number, curvature parameter, and radiation parameter. On the other hand, it declined for the Prandtl number and power law index. Similarly, the concentration profile increases for the activation energy, reaction rate, and temperature difference parameter, but it decreases for the curvature parameter and Schmidt number.

Impacts of activation energy and electroosmosis on peristaltic motion of micropolar Newtonian nanofluid inside a microchannel

This study investigates the impact of electroosmosis on the peristaltic flow of unsteady micropolar nanofluid with heat transfer. The findings could enhance the design of peristaltic pumps, potentially improving drug delivery systems, simulations of blood flow in medical devices, and cancer treatments. The fluid under investigation adheres to a micropolar model and flows through a microchannel that exhibits peristalsis along its walls. Moreover, the system is subjected to various external effects, including a uniform magnetic field, the electroosmotic phenomenon, heat absorption, and a chemical reaction with activation energy. Consequently, the problem is mathematically modulated by a system of nonlinear partial differential equations governing the velocity, temperature, and nanoparticle concentration. By employing wave transformation, these governing equations are reduced to ordinary differential equations (ODEs). The reduced equations were solved both analytically, using the homotopy perturbation method, and numerically, using the Runge–Kutta–Merson method. A comparison was made between the solutions, which were found to be closely aligned. Furthermore, a series of figures were employed to provide visual representation and discussion of the implications of the physical properties. The calculations reveal that the electroosmotic flow (EOF) enhances the axial flow of the micropolar fluid along the direction of the applied electric field. It is also observed that the increase in the activation energy (which indicates a low reaction rate) increases the concentration profile whereas the increase in the reaction rate parameter reduces the concentration profile. Additionally, the spin velocity of the particles is diminished by either an increase in the magnetic parameter or the coupling parameter.

Multiscale modeling of reactive flow in heterogeneous porous microstructures

This paper presents a multiscale reactive flow model to simulate in-situ leaching of copper in heterogeneous porous microstructures. The introduced workflow combines fluid flow simulation with advection-diffusion-reaction simulation, both required to model reactive flow. The proposed workflow can include the fluid flow in resolved and unresolved pore structures and utilizes required parameters from molecular simulation (ionic diffusivity) and reaction databases (reaction rate parameters). The modeling approach is validated by comparing results to other open-source codes for a model calcite dissolution on acid injection. This model is applied to copper mining by leaching to analyze the reactive flow through a fractured digital rock model of a subsurface sample. Results are analyzed by tracking the concentration distribution along the pore space structure and calculating the outlet concentration of copper to conform the leaching path. Several sensitivity studies are performed to show the robustness of the modeling framework as well as to investigate the importance of each of these parameters on copper production. The complexity of the model is systematically increased from a single scale surface reaction model, to consider the influence of competitive bulk solution reactions, and finally to include flow through porous media to model multiscale reactive flow. This study shows that a multi-scale flow model with homogeneous bulk and heterogeneous surface reactions is required to accurately model copper leaching.

Universal Glycosyltransferase Continuous Assay for Uniform Kinetics and Inhibition Database Development and Mechanistic Studies Illustrated on ST3GAL1, C1GALT1, and FUT1.

Chemical systems glycobiology requires experimental and computational tools to make possible big data analytics benefiting genomics and proteomics. The impediment to tool development is that the nature of glycan construction and mutation is not template driven but rests on cooperative glycosyltransferase (GT) catalytic synthesis. What is needed is the collation of kinetics and inhibition data in a standardized form to make possible analytics of glycan and glycoconjugate synthesis, mechanism extraction, and pattern recognition. Currently, kinetics assays in use for GTs are not universal in processing nucleoside phosphate UDP, GDP, and CMP donor-based glycosylation reactions due to limitations in accuracy and large substrate volume requirements. Here we present a universal glycosyltransferase continuous (UGC) assay able to measure the declining concentration of the NADH reporter molecule through fluorescence spectrophotometry and, therefore, determine reaction rate parameters. The development and parametrization of the assay is based on coupling the nucleotide released from GT reactions with pyruvate kinase, via nucleoside diphosphate kinase (NDK) in the case of NDP-based donor reactions. In the case of CMP-based reactions, the coupling is carried out via another kinase, cytidylate kinase in combination with NDK, which phosphorylates CMP to CDP, then CDP to CTP. Following this, we conduct kinetics and inhibition assay studies on the UDP, GDP, and CMP-based glycosylation reactions, specifically C1GAlT1, FUT1, and ST3GAL1, to represent each class of donor, respectively. The accuracy of calculating initial rates using the continuous assay compared to end point (noncontinuous) assays is demonstrated for the three classes of GTs. The previously identified natural product soyasaponin1 inhibitor was used as a model to demonstrate the application of the UGC assay as a standardized inhibition assay for GTs. We show that the dose response of ST3GAL1 to a serial dilution of Soyasaponin1 has time-dependent inhibition. This brings into question previous inhibition findings, arrived at using an end point assay, that have selected a seemingly random time point to measure inhibition. Consequently, using standardized Km values taken from the UGC assay study, ST3GAL1 was shown to be the most responsive enzyme to soyasaponin1 inhibition, followed by FUT1, then C1GALT1 with IC50 values of 37, 52, and 886 μM respectively.

Thermodynamic case study of boundary layer viscous nanofluid flow via a riga surface by means of finite difference method

The Riga plate is an electromagnetic actuator made out of permanent magnets and alternating electrodes on a flat surface. In the boundary layer flow across the Riga Plate, viscous dissipation is surveyed in this paper. The suitable boundary conditions have been assigned to the governing model for mass and heat convection phenomenon. A governing equation can be converted into non-dimensional form using similarity transformations. To create numerical solutions to physical phenomena, the finite difference approach can be utilized. Extensive graphical illustrations are provided for the effects of the buoyancy coefficient parameter, modified Hartmann number, parameter related to electrode and magnet width, Prandtl number, slip parameter, thermophoretic parameter, thermal radiation parameter, Schmidt number, chemical reaction rate parameter, suction parameter, Brownian motion parameter, volume fraction, Biot number, and Eckert parameter on velocity, temperature, and concentration distributions. By varying the Eckert number, the viscous dissipation effects can be obtained. Suction and slip parameters increase the velocity while decrease the temperature in both nanofluid cases. The high temperature and velocity of equally distributed nanofluids rise as the volume fraction increases. Thermal radiation promotes heat transport. The concentration of nanoparticles in the region around the plate increases as the chemical reaction parameter increases. The research findings are useful for thermal engineers and practitioners involved in the design and optimization of systems where boundary layer fluxes and heat transfer are important factors. Understanding the effects of viscous dissipation can lead to more reliable heat transfer estimates and more effective thermal management in real-world structures.

Polytetrafluoroethylene (PTFE) burn characteristics and toxicant formation in an oxidizer cross-flow via laser absorption tomography

A two-dimensional solid-fuel combustion experiment for fire-resistant polymers under forced convective cross-flow was developed to assess burn characteristics and toxicant formation using advanced laser absorption diagnostics that enable in situ species and temperature measurements near the fuel surface. The method was used to examine the thermochemical flow-field structure near the surface of polytetrafluoroethylene (PTFE) exposed to a well-defined solid-fuel pilot flame burning polymethyl methacrylate (PMMA). Infrared diode and quantum cascade lasers were used to probe rovibrational absorption transitions of hydrogen fluoride (HF) and carbon monoxide (CO), respectively, at the exit plane of a heterogeneous cylindrical fuel grain from which temperature and mole fraction could be inferred. A laser absorption tomography (LAT) technique with a Tikhonov-regularized Abel inversion was applied to reconstruct radially-resolved profiles in the axisymmetric reacting flow which, when compiled across a range of fuel lengths, provided a two-dimensional image of the near-surface reaction layer. Thermochemical data and reaction rate parameters from existing fluorocarbon chemistry models were used to generate high-temperature simulations of product species concentrations and temperature as a function of oxidizer-to-fuel ratio to elucidate observed trends and identify key reactions relevant to the novel dataset. The geometry and scale of the composite fuel experiments is intended to be tractable for reactive multi-physics models, enabling quantitative comparison of combustion characteristics and ultimately improved predictive capability of toxicant quantities resulting from fluoropolymer combustion in fire environments.

Surface kinetics and pressure dependence of propane oxidation over platinum

The catalytic total oxidation of propane over platinum was investigated experimentally and numerically at pressures of 1–7 bar and catalyst temperatures up to 700 K. A wire microcalorimeter was employed to determine the global rate parameters of the catalytic reaction within the kinetically controlled regime. For 1 bar pressure, the dissociative adsorption of C3H8 on Pt and its subsequent decomposition were modeled as two lumped steps based on global reaction parameters. A detailed and thermodynamically consistent catalytic mechanism was constructed by incorporating these lumped steps with an existing atmospheric-pressure H-C2 elementary reaction model. Two-dimensional CFD simulations using the developed global and detailed reaction mechanisms closely reproduced the measured heat release rates. The intricate dependence of catalytic ignition and reactivity on pressure was further elucidated. Ignition temperatures were found to be linearly correlated to pressures, due to the weaker net adsorption of oxygen compared to that of propane, which progressively aggravated at higher pressures and in turn hindered ignition. More importantly, a non-monotonic pressure dependence of the C3H8 catalytic reactivity on Pt, which gradually diminishes with increasing temperatures, is reported for the first time. The temperature range of this non-monotonic behavior (< 650 K) is of special importance for part-load and idling operations of gas turbines using hybrid hetero-/homogeneous combustion approaches and for normal operations of recuperative microreactors. Thus, this work provides key information for the design and optimization of such devices utilizing Pt as catalyst.

The magnetic dipole-induced ternary-hybrid nanofluid flow behavior along a vertical and horizontal wall under free, mixed, and forced convection

In the field of nanotechnology research, fluid–nanoparticle interaction is attracting a lot of attention. A wide variety of technological and industrial areas that include convection flows, low-velocity heat exchangers, emergency shut nuclear reactors, exposed solar receivers to wind currents, and fans cooling electronic equipment. The flow of ternary-hybrid nanofluid (NF) due to forced, mixed, and free convection comprising platelet, cylindrical, and spherical shaped nanoparticles is explored in this study. Nonlinear governing equations are changed into ordinary differential equations (ODEs) by employing the proper similarity variables. The numerical outcomes of the reduced equations are attained using a shooting method and the Runge–Kutta–Fehlberg 45 (RKF-45) order. Graphical displays are used to convey the numerical results. It is investigated how the various parameters affect each profile. Results reveal that the velocity for the forced convection case near the surface declines faster than the free and mixed convection case for distinct values of the porosity parameter. The heat transport for the free convection case shows less heat transport than the forced and mixed convection case. The mass transport for the forced convection case shows improved mass transport than the free and mixed convection case for distinct values of chemical reaction rate parameter.

Multivariate modeling of intrinsic kinetics for gas-solid heterogeneous photocatalytic reaction: A general method for different pollutant-photocatalyst systems

A reactor model that can interpret the effects of multiple variables on photocatalytic performance is crucial to bridging the gap between lab- and commercial-scale reactors. However, there is no explicit expression to simultaneously describe the relationships between reaction rate and operating parameters including initial concentration, flow rate, light intensity, relative humidity, and catalyst dosage. Therefore, this work presents a multivariate reactor model that extensively describes the effects of these quantities on reaction rate. First, the model is developed by resolving the Navier-Stokes equations coupled with the convection-diffusion equations and an improved reaction kinetics expression. Then, the particle swarm optimization (PSO) algorithm is integrated with the numerical simulation of velocity and concentration fields to determine intrinsic kinetic parameters. Subsequently, the multivariate model for NO degradation is experimentally validated. In addition, the versatility of the proposed modeling method is evidenced by the experimental data of different photocatalyst-pollutant systems from literature. The model predictions agree with experimental results well with the R2 values of 0.949–0.995. Furthermore, a CFD simulation is executed to understand the interactive effects of fluid flow, mass transfer, and kinetic reaction to guide reactor optimization. Finally, the model for NO removal using UiO-66-NH2 in the current study outperforms several reported NO removal models with the smallest RMSE of 2.57% and MAPE of 2.74%. It is concluded that the proposed modeling method could successfully predict the performance of different gas-solid or liquid-solid heterogeneous reactions.