Arrhenius Rate Equation Research Articles

Sustainable Treatment of Emerging Organic Pollutants (Eops), Endocrine Disruption Chemicals (Edcs) from Water & Waste Water and Role of AIU Online Based Distance Learning Education System to Achieve UNESCO 2030 Goals Towards Sustainable Development

Complete mineralization of EOPs including EDCs is one of the challenges towards sustainable management practice of water and waste water treatment systems. Ozone gas has been identified as an effective oxidant against mineralization of these chemicals. Optimization of factors affecting ozonolysis is vital towards mineralization of EDCs. For this kinetic study of ozonolysis degradation of EDCs in two phase gas-liquid systems is performed in a semi[1]batch reactor observing Total Organic Carbon (TOC) degradation for process optimization. Concentration of initial substances, temperature of the system and sparger/bubble size have significant effect on ozonolysis of EDCs. They are considered as dominant factors to be optimized. Temperature dependency of specific kinetic constants of model EDCs, i.e., Diclofenac Sodium (DFS) has been determined by taking into account the specific volume change due to ozone dosing. From this the activation energy for DFS has been determined to be 26.4 KJ/mol using the well known Arrhenius rate equation. These information together with sparger effect have been incorporated to find optimum values of the process variables for ozonolysis of EDCs in water and wastewater without using any catalyst so that the simplicity of the ozonolysis process can be preserved. Results obtained in work will help water treatment industries to develop sustainable ozonolysis technique to treat EDCs at optimized process condition.

인공신경망을 이용한 반응유동 수치해석의 반응기구 대체 연구

Reducing the computational cost of chemical kinetics is essential to implement detailed reaction mechanisms into realistic numerical simulations. The present study introduces an artificial neural network (ANN) that can predict the chemical source terms of each species for the given species mass fractions and temperature, replacing the conventional chemical terms based on Arrhenius rate equations. The ANN was trained using numerical solutions of opposed-flow flames that can cover a wide range of combustion problems. The OPPDIF code and a detailed reaction mechanism for hydrogen and air with 9 species and 19 reactions were used to generate a training dataset comprised of species mass fractions, temperature, chemical source terms. A physics-guided loss function that considers mass conservation of elemental species was employed. Using the trained ANN, a modified OPPDIF, named OPPDIF-ANN, was prepared by replacing the CKWYP with CKWYP-ANN evaluating the chemical sources via the trained ANN. For multiple global strain rate conditions, the solutions using ANN-based source terms were proven to be identical to those using Arrhenius source terms.

Effects of target temperature on thermal damage during temperature-controlled MWA of liver tumor

Microwave ablation (MWA) is one among the cancer treatment techniques applied in clinical treatment. This technique is based on rising the temperature within the tissue and the radiation dose absorbed by the cells. The goal of this study is to improve the accuracy of temperature simulation during temperature-controlled MWA of liver tumor. A two-dimensional numerical model of liver tissue has been built and solved using the Finite Element Method (FEM). The bio-heat equation, the first-order Arrhenius rate equations, and the Maxwell equations are employed to simulate the cancer cells necrosis. For heat control, an input microwave power source was controlled by a proportional-integral-derivative (PID) controller to keep the target tip temperature below the preset temperature value during MWA. The effect of the target tip temperature on the applied input microwave power has been investigated in liver tissue. Further, the thermal damage fraction and the time required for complete necrosis liver cancer are also evaluated. The present results show that the specific absorption rate (SAR) and the temperature distribution are highly influenced by the target tip temperature. Optimal treatment period for total tumor ablation will offers a significant way to reduce damage to the surrounding healthy cells and providing safe use of MWA and without risk.

Numerical Investigation of Tissue-Temperature Controlled System in Thermal Ablation: A Finite Element Approach

In thermal ablation, several techniques of treating infected cell in human tissue are being used by the physicians. Transferring heat to the infected cell is one of them. The purpose of this research is to investigate the tissue-temperature controlled system in thermal ablation and compare with two different point heating processes, namely constant and step heating. For this purpose, the finite element model of Penne’s bio-heat equation has been developed to measure the temperature within the two-dimensional tissue model embedded with a small tumor. The tissue temperature-controlled heating was designed to restrict the healthy tissue temperature below the damage threshold temperature. Using the temperature profile, tissue damage index was measured with the help of Arrhenius rate equation. The results show that the tissue temperature-controlled system reduces the temperature of healthy tissue nearby the infected cell to 40% compare to constant and step point heating. This system keeps the healthy tissue within the threshold value (43oC) up to 1000s when it is 100s for other two techniques. After 200s, healthy tissue nearby the infected cell start to damage for constant and step point heating. But temperature-controlled system always keep the healthy tissue safe. The results of this research conclude the temperature-controlled system a better heating technique to remove the infected cell. The information published in this paper will be helpful for the physicians and bio-medical engineers to treat the infected cell or to design medical equipment.

Multilayer Backsheet Characterization Using Diffusion Experiments and Optimization Method for Water Diffusion Simulation Inside the Photovoltaic Module

Photovoltaic (PV) modules are expected to be durable against exposure to outdoor environments for prolonged time durations. One of the primary causes for the loss of durability is water exposure. Water concentration prediction within the PV module is challenging under the varying environmental conditions as well as the multilayer nature of the backsheet. Therefore, there is a need for systematic multilayer water diffusion characterization of backsheet as well as to incorporate the varying environments in the water diffusion simulations of the PV module. In this article, backsheet is considered as a two-layer laminate whose water diffusion parameters were determined using both water diffusion experiments (without separation of each layer) and an optimization technique. The gravimetric technique was used to measure experimental water mass uptake of the backsheet, whereas Fick's second law based diffusion model was used to predict numerical water mass uptake. An optimization technique was used to determine the water diffusion and solubility coefficients that minimized the difference between the numerical and experimental water mass uptake. The optimized water diffusion and solubility coefficients in the test range of 24–50 °C reasonably fitted the Arrhenius rate equations. Backsheet was also considered as a homogeneous configuration that was used to determine the effective water diffusion parameters. These effective parameters were found to be significantly different from the optimized parameters of the two-layer backsheet model. Water diffusion simulations with a commercial PV module exposed to outdoor environment showed significant differences in the water concentration between the two-layer and homogeneous backsheet models.

Water diffusion simulation in photovoltaic module based on the characterization of encapsulant material using in-situ gravimetric technique

Durability of photovoltaic (PV) module under outdoor exposure is predominantly controlled by the ambient humidity, temperature, and ultraviolet (UV) irradiation as well as the mechanical and thermal stresses. Outdoor exposure with multiple cycles of water absorption and desorption degrades the PV module materials as well as their interfaces. This water diffusion behavior, when characterized through reliable and realistic methods, can be used to accurately predict the water concentration within the PV module and thereby help to predict the water-induced degradation in PV module. An in-situ gravimetric method was used in this study to characterize the effects of temperature on the water diffusion behavior of ethylene vinyl acetate (EVA). Both water absorption and desorption in the EVA showed a simple Fickian behavior. The water diffusion and solubility coefficients determined from in-situ gravimetric experiments in the test range of 24°–50 °C reasonably fitted the Arrhenius rate equations with an activation energy of 30.64 kJ/mol and heat of solution −16.86 kJ/mol, respectively. Finally, the data from the in-situ gravimetric technique was used to simulate and compare the water diffusion within a glass-glass PV module laminate where exposed to accelerated and Delhi outdoor environments. Water penetration depth is limited to about 50 mm for the ten cycles of the humidity freeze test, while it extends to about 110 mm for both 1000 h of damp heat test and one-year outdoor environment.

Effect of devolatilization model on flame structure of pulverized coal combustion in a jet-burner system

A numerical simulation was performed with the two competing model in the devolatilization process for a pulverized coal combustion jet flame by means of LES. The target was a simple jet burner flame in CRIEPI. To solve the LES equations, a CFD code FFR. Comb was employed with the dynamic Smagorinsky SGS turbulent model. A simple global kinetic mechanism was implemented to predict combustion of the gas and solid phase combustion. The interactions between the two phases were calculated by PSI-Cell model while the reaction rate in turbulent flow was established by SSFRRM. The simulation was validated by comparing results to the experimental data in terms of particle dispersion and velocity as well as gaseous velocity. The flame structure was discussed with temperature, mole fraction of major species. In addition, the effect of the devolatilization model was investigated simultaneously by comparing to another simulation that employed the single first order reaction model because the devolatilization was one of the major processes in coal combustion and it had an influence on the flame structure from all reactive regions. The release rate was calculated by two different parameter sets in the Arrhenius rate equation for the two competing model that were corresponding different temperature regions whereas the released rate was determined by only one fixed parameter set in the single first order reaction model. From the simulation, it was revealed that the main reactions took place at the upstream and the first fuel oxidation was stronger at the inner reaction zone comparing to the far side combustion. It was confirmed as well that the two competing model could capture the quick devolatilization faster than the single first order reaction model though the dominant part appeared later than the single first order reaction model.

Effect of spatial inhomogeneities on detonation propagation with yielding confinement

The propagation of detonations in layers of reactive gas bounded by inert gas is simulated computationally in both homogeneous and inhomogeneous systems described by the two-dimensional Euler equations with the energy release governed by an Arrhenius rate equation. The thickness of the reactive layer is varied and the detonation velocity is recorded as the layer thickness approaches the critical value necessary for successful propagation. In homogeneous systems, as activation energy is increased, the detonation wave exhibits increasingly irregular cellular structure characteristic of the inherent multidimensional instability. The critical layer thickness necessary to observe successful propagation increases rapidly, by a factor of five, as the activation energy is increased from $$E_\mathrm{a}/RT_0 = 20$$ –30; propagation could not be observed at higher activation energies due to computational limitations. For simulations of inhomogeneous systems, the source energy is concentrated into randomly positioned squares of reactive medium embedded in inert gas; this discretization is done in such a way that the average energy content and the theoretical Chapman–Jouguet (CJ) speed remain the same. In the limit of highly discrete systems with layer thicknesses much greater than critical, velocities greater than the CJ speed are obtained, consistent with our prior results in effectively infinite width systems. In the limit of highly discretized systems wherein energy is concentrated into pockets representing 10% or less of the area of the reactive layer, the detonation is able to propagate in layers much thinner (by an order of magnitude) than the equivalent homogeneous system. The critical layer thickness increases only gradually as the activation energy is increased from $$E_\mathrm{a}/R T_0 = 20{-}55$$ , a behavior that is in sharp contrast to the homogeneous simulations. The dependence of the detonation velocity on layer thickness and the critical layer thickness is remarkably well described by a front curvature model derived from the classic, ZND-based model of Wood and Kirkwood. The results of discrete sources are discussed as a conceptual link to the behavior that is experimentally observed in cellular detonations with highly irregular cellular structure in which intense turbulent burning rapidly consumes detached pockets behind the main shock front. The fact that highly discrete systems are well described by classical, curvature-based mechanisms is offered as a possible explanation as to why curvature-based models are successful in describing heterogeneous, condensed-phase explosives.

Numerical investigation of convective cooling in minimizing skin burns during radiofrequency ablation of breast tumor

Skin burns is one of the most common complications reported during treatment of early-stage breast cancer with radiofrequency ablation (RFA) technique. In this regard, the present study aims to analyze the efficacy of forced convection surface cooling in minimizing the skin burns during RFA of breast tumor. The study considers a heterogeneous three-dimensional numerical model of breast that has been constructed based on the anatomical details available in the literature. A spherical tumor of 1.5 cm has been embedded in the numerical model of breast to represent in-situ tumor in its early stage. A programmable temperature-controlled RFA has been performed by incorporating the closed-loop feedback PID controller into the numerical model. The thermo-electric analysis has been performed using a finite element based commercial solver COMSOL Multiphysics® to obtain the temperature distribution by incorporating the coupled electric field distribution, Pennes bioheat equation and Arrhenius rate equation. The temperature dependent electrical and thermal conductivities of both the tissue and tumor along with damage dependent perfusion rate have been incorporated to achieve better correlation with the clinical RFA. The numerical simulation results revealed that, there is a significant reduction in the temperature at outer periphery of breast with increase in convective heat transfer coefficient. Further, the effects of variation in surface cooling on temperature distribution, input voltage requirement and treatment time required for complete tumor necrosis have been studied. The simultaneous application of forced convective surface cooling along with RFA could play a vital role in addressing the most common complication of skin burns during treatment of breast cancer.

Numerical study to establish relationship between coagulation volume and target tip temperature during temperature-controlled radiofrequency ablation

ABSTRACTThe present study aims at proposing a relationship between the coagulation volume and the target tip temperature in different tissues (viz., liver, lung, kidney, and breast) during temperature-controlled radiofrequency ablation (RFA). A 20-min RFA has been modelled using commercially available monopolar multi-tine electrode subjected to different target tip temperatures that varied from 70°C to 100°C with an increment of 10°C. A closed-loop feedback proportional-integral-derivative (PID) controller has been employed within the finite element model to perform temperature-controlled RFA. The coagulation necrosis has been attained by solving the coupled electric field distribution, the Pennes bioheat and the first-order Arrhenius rate equations within the three-dimensional finite element model of different tissues. The computational study considers temperature-dependent electrical and thermal conductivities along with the non-linear piecewise model of blood perfusion. The comparison between coagulation volume obtained from the numerical and in vitro experimental studies has been done to evaluate the aptness of the numerical models. In the present study, a total of 20 numerical simulations have been performed along with 12 experiments on tissue-mimicking phantom gel using RFA device. The study revealed a strong dependence of the coagulation volume on the pre-set target tip temperature and ablation time during RFA application. Further, the effect of target tip temperature on the applied input voltage has been studied in different tissues. Based on the results attained from the numerical study, statistical correlations between the coagulation volume and treatment time have been developed at different target tip temperatures for each tissue.

Effect of different breast density compositions on thermal damage of breast tumor during radiofrequency ablation

The present study analyzes the efficacy of radiofrequency ablation (RFA) of breast tumor with different breast density levels {viz., extremely dense (ED), heterogeneously dense (HD), scattered fibroglandular (SF) and predominantly fatty (PF)}. A spherical tumor of 1.5cm has been embedded at various locations in the heterogeneous three-dimensional numerical breast model to represent in situ early stage tumor. Temperature-controlled RFA has been performed by incorporating the proportional-integral-derivative (PID) controller. A thermo-electric analysis has been done to obtain the temperature distribution and the ablation volume by incorporating the coupled electric field distribution, the Pennes bioheat and the first-order Arrhenius rate equations. The effects of temperature-dependent changes in electrical and thermal conductivities of heterogeneous multi-layer breast models have been considered. The non-linear piecewise model of blood perfusion has been incorporated to achieve better correlation with the clinical RFA. The numerical results have been validated with the in vitro experimental results. The results revealed that, the breast density compositions significantly affect the treatment outcomes in terms of ablation volume and temperature distribution. It has been found that, the breast with lower fatty tissue requires significantly less time to attain complete tumor necrosis as compared to the breast with higher fat content.

Effect of chemical diagenesis on pore pressure in argillaceous sediment

I present a model of pore pressure for argillaceous sediment that integrates the well-known undercompaction mechanism with the lesser-known chemical diagenesis mechanism. The model is based on a generalized compaction model, first-order chemical rate theory and Arrhenius rate equation, and a simple thermal-history model. The parameters of this model (activation energy, E, and the pre-exponential factor, A) are obtained from published X-ray diffraction data. I also present models for bulk density and velocity of sediment that are guided by rock-physics principles. I also discuss the relation between the current model and the Bowers model, which noted the importance of the thermal mechanisms in the context of pore-pressure prediction.

Graphical methods for the analysis of shear-induced detachment of cells and microorganisms.

Treating shear stress induced detachment of micro-organisms as a bond breaking mechanism, the authors present three intuitive graphical approaches to determine the relevant parameters in the Arrhenius rate equation, i.e., attachment energy, prefactor, and maximum shear stress. They demonstrate the methods with the detachment of polystyrene spheres and show that having three different methods presents the opportunity to check the consistency of the results.

Determination of Mannitol Decomposition Rate under Hydrothermal Pretreatment Condition

For utilization of kelp, which is produced abundantly in Japan, recovery of mannitol is important because mannitol is a main component of kelp. Mannitol can be recovered into liquid phase by hydrothermal pretreatment of kelp, but when treatment condition is too severe, decomposition of the product mannitol also takes place. To determine the optimum condition for hydrothermal pretreatment, determination of mannitol decomposition rate is indispensable. The purpose of this study is to determine decomposition rate parameters of mannitol under hydrothermal conditions for mannitol recovery from kelp without concomitant decomposition. The decomposition rate was successfully determined using a flow reactor, and the rate constant was expressed with a first-order Arrhenius rate equation with a pre-exponential factor of 3.23 s−1 and activation energy of 26.5 kJ/mol. The obtained reaction rate predicted the behavior of mannitol during hydrothermal pretreatment of kelp with average error of 4.6 %.

Air–steam gasification of biomass in fluidized bed with CO2 absorption: A kinetic model for performance prediction

Significance of decarbonized energy production in the context of a foreseeable hydrogen economy has called for the need of extensive research in biomass gasification-carbon dioxide capture technique. The feasibility of calcium oxide as a sorbent for CO2 in syngas is studied for air–steam fluidized bed (FB) gasification through a reaction kinetic modeling approach. Arrhenius rate equations are employed for primary and secondary pyrolysis, gasification and carbonation reactions. Devolatilization product yields are predicted using available correlations for FB gasification and cracking of tar is incorporated. Parametric performance analysis is carried out highlighting the significance of equivalence ratio (ER), gasification temperature, steam to biomass ratio (SBR) and sorbent to biomass ratio (SOBR). The effects of various gasifying media on H2 concentration and performance indicators such as heating value and efficiencies are analyzed. The simulation results are validated with the reported experimental results. The kinetic study reveals that air–steam gasification significantly reduces the unreacted steam but at a lower H2 concentration than steam gasification. A maximum of 53% hydrogen rich gas mixture is predicted at ER = 0.25, SBR = 1.5, SOBR = 2.7 and 1000 K. Against fossil fuel expended steam gasification, pure oxygen gasification is suggested by the study.

Oxidation rate of graphitic matrix material in the kinetic regime for VHTR air ingress accident scenarios

Data on oxidation rates of matrix-grade graphite in the kinetically-controlled temperature regime of graphite oxidation are needed for safety analysis of High Temperature Gas Cooled Reactors and Very High Temperature Reactors. In this work, the oxidation rate of graphitic matrix material GKrS was measured thermogravimetrically for various oxygen concentrations and with temperatures from 873 to 1873K. A semi-empirical Arrhenius rate equation was also developed for this temperature range. The activation energy of the graphitic material is found to be about 111.5kJ/mol. The order of reaction was found to be about 0.89. The surface of oxidized GKrS was characterized by Scanning Electron Microscopy, Electron Dispersive Spectroscopy, Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy.

Analytical Model of CeO2 Oxidation and Reduction

In this work, an Arrhenius-based model for the high-temperature reduction and oxidation of CeO2 is developed. The model is shown to agree well with both literature data for the equilibrium oxygen vacancy concentration and novel experimental kinetics of oxidation and reduction obtained by the authors. The form of the Arrhenius rate equation was determined from the properties of the reaction. Equilibrium data from the literature was analyzed with respect to our rate equation. From this analysis, a number of constraints on the model parameters were determined, and some of the constants of the model were fixed. The model accurately predicts the equilibrium composition of CeO2 over a wide range of oxygen partial pressures (10–2 to 10–8 bar) and temperatures (1000–1900 °C). Novel results of the experimental reoxidation of ceria were analyzed to fix the remainder of the constants. Porous cerium dioxide pellets produced by the authors were reduced at high temperature (1650 °C) and low oxygen partial pressure (10–...

Oxidation rate of nuclear-grade graphite NBG-18 in the kinetic regime for VHTR air ingress accident scenarios

One of the most severe accident scenarios anticipated for VHTRs is an air ingress accident caused by a pipe break. Graphite oxidation could be severe under these conditions. In this work, the oxidation rate of NBG-18 nuclear-grade graphite was studied thermogravimetrically for different oxygen concentrations and with temperatures from 873 to 1873K. A semi-empirical Arrhenius rate equation was developed for the temperature range of 873–1023K. The activation energy of NBG-18 was 187kJ/mol and the order of reaction was 1.25. The penetration depth of oxidant was about 3–4mm for NBG-18 oxidized at 973K. Increased porosity and changes in external geometry became more prominent at higher temperatures from about 1173 to 1873K. The surface of oxidized NBG-18 was characterized by SEM, EDS, FTIR and XPS.

Finite element method simulations of heat flow in fixed bed solar water splitting redox reactors

An improved design for radiation absorption and heat flow into materials with low thermal conductivity is demonstrated. The design was developed for application in fixed bed two step solar water splitting redox reactors. The fixed bed was assumed to be made from porous ceramic. The low thermal conductivity of the porous ceramic redox material is compensated for by changing the profile of the fixed bed. The profiling used was wedges cut into the material which allows concentrated solar radiation to be incident on a larger area of redox material than for a flat monolith design. The design is demonstrated to efficiently transfer heat to the bulk and greatly reduce re-radiation. For a wedge 9 cm in depth and 1.6 cm wide at the opening, heated with 500kWm−2 incident radiation for 300s, approximately double the amount of radiation is absorbed. The effects of thermal conductivity, emissivity and scaling on the efficiency of the design were investigated. The radiation absorption performance improved when scaled up. The improvement of the design over a flat plain bed is greater for lower emissivity. The improvement provided by the wedge design was found to decrease for increasing thermal conductivity, and eventually for high conductivity values it reduced performance. Using this method a larger amount of material with low thermal conductivity can be heated with the same power input and reduced radiation losses. The heat flow simulations were then coupled to an Arrhenius rate equation to investigate the possible improvement to the reaction efficiency and yield offered by the wedge design. Over a time of 300s the efficiency and yield were seen to be approximately a factor of 4 times higher in the wedge case. Finally a concentrated solar cavity reactor based on the design is proposed.

Al<SUB>2</SUB>O<SUB>3</SUB>/TiO<SUB>2</SUB> Multilayer Passivation Layers Grown at Low Temperature for Flexible Organic Devices

In this study, the permeability of passivation layers consisting of aluminum oxide (Al2O3) and titanium oxide (TiO2) was examined. The films were deposited on poly(ether sulfone) (PES) substrates via electron cyclotron resonance atomic layer deposition (ECR-ALD) at various deposition temperatures. The optimum plasma power and deposition temperature were investigated through measurements of the refractive index and packing density of the Al2O3 and TiO2 films. A buffer layer/multilayer structure was proposed in this study to improve the passivation barrier performance. A low water vapor transmission rate (WVTR) of approximately 5 x 10(-3) g/m2 x day was achieved with two Al2O3/TiO2 stacks with thicknesses of 40 nm deposited at 80 degrees C. Based on the Arrhenius rate equation, the activation energy of water vapor transmission through different passivation structures was examined. The activation energies of Al2O3, Al2O3/TiO2, and two Al2O3/TiO2 stacks with thicknesses of 40 nm were 51.8, 63.9, and 74.7 kJ/mol, respectively.