Thermal Reaction Research Articles

Entropy generation outcomes in peristalsis of Carreau–Yasuda nanofluid flow with activation energy

AbstractThis paper focuses on the study of activation energy and entropy generation in the peristaltic flow of a Carreau–Yasuda nanofluid. Peristaltic transport, coupled with entropy generation and activation energy in a curved geometry, has significant applications in biomedical and industrial processes involving non‐Newtonian fluids. Blood flow in the arteries, the movement of chyme in the gastrointestinal tract, and peristaltic motion replicate the natural muscular contractions that drive fluid flow in the physiological systems. The integration of entropy generation allows for the evaluation of energy efficiency and the analysis of losses due to viscous dissipation. Activation energy plays a crucial role in processes such as drug delivery, where temperature‐sensitive reactions or biochemical changes affect fluid behavior. In industrial applications, like peristaltic pumps in chemical reactors or polymer processing, the consideration of entropy and activation energy aids in optimizing thermal management and reaction rates. The mathematical model is developed under these assumptions, and the governing equations are numerically solved using the NDSolve function in Mathematica. Graphical results show that higher activation energy and concentration reduce the reaction rate, while the Bejan number and entropy generation increase with a larger Brinkman number. Velocity and temperature increase under slip conditions, whereas concentration decreases, and a stronger radial magnetic field reduces both velocity and the size of the trapped bolus.

Mechanism of methyl elaidate on the thermal oxidation behavior

The effects of cis–trans isomerization on the oxidation products of oleic acid (composites and structure characterization) were investigated. The reduction of thermal oxidation reaction of methyl elaidate (ME) was 6.72 % lower than that of methyl oleate (MO), and the oxidation products (core aldehydes) first increased and then decreased with the prolongation of thermal oxidation time. ME exhibited better oxidation stability than MO in free radicals, hydroperoxides, double bonds, aldehydes, and glycerides. The oxidation products were mainly 11-oxo-9-undecenoate (initial stage) and methyl 9-oxononanoate (later stage), following the free radical chain reaction mechanism. The H8 in double bond was more easily dehydrogenated in the chain initiation stage than H11, followed by the formation of core aldehyde through three intermediates and two transition states each pathway. ME required a higher energy barrier (1.3–13.6 kJ/mol) than MO reaction, making it more difficult for ME to undergo thermal oxidation reaction. The transition state 4 and 5 were rate determining steps of chain initiation reaction and proliferation reaction, respectively. This study was of great significance to further control the formation of these trans fats and their oxidation products.

Study of MHD Casson Nanofluid Flow Over an Inclined Stretching Sheet in Porous Media with Thermal Slip, Chemical Reaction and Radiation Effects

In the current study, the behaviour of Casson nanofluid subjected to magnetohydrodynamic (MHD) flow across an inclined stretched sheet within a porous medium has been investigated numerically. The governing equations are transformed into ordinary differential equations with the corresponding boundary conditions by employing similarity transformations. The solutions of essential equations are achieved by using the 4th-order Runge-Kutta method combined with the shooting technique. The novelty and innovative contribution are showcased through illustrative graphs that scrutinize the effect of factors that impact the velocity, temperature, and concentration profiles within assorted flow scenarios. The primary focal points of the study encompass examining variations in magnetic field strength, angle of inclination, and suction intensity that affect the fluid's velocity moderation, while improved porosity and radiation parameters lead to a rise in fluid temperature. Higher Biot numbers correlate with an increase in fluid temperature. The implications of positive coefficients of heat transfer are crucial across various fields to ensure efficient thermal management ensuring optimal performance and longevity. The numerical data presented is aligned with earlier published results for comparison. Furthermore, the variations in skin friction, Nusselt, and Sherwood numbers driven by different parameters are displayed in tables to highlight significant modifications.

Improving In Situ Combustion for Heavy Oil Recovery: Thermal Behavior and Reaction Kinetics of Mn(acac)3 and Mn-TO Catalysts

In this research work, the catalytic performances of two manganese-based catalysts, manganese (III) acetylacetonate (Mn(acac)3) and manganese tallate (Mn-TO), were studied during the process of Ashalcha heavy oil oxidation under in situ combustion conditions. DSC analysis shows distinct thermal behavior of both ligated catalysts during low- and high-temperature oxidation phases (LTO and HTO); for example, the shifting in peak temperature (Tp) in the HTO at a heating rate of 10 °C/min was reduced by approximately 5.3% for Mn-TO and 2.24% for Mn(acac)3 when compared with uncatalyzed heavy oil. Combined isothermal kinetic analyses using the Friedman and Kissinger–Akahira–Sunose analytic methods have provided insights about activation energies and frequency factors over the whole conversion range, where the catalytic performance of Mn-TO showed low activation energies in both LTO and HTO (Eα of Mn-TO was approximately 13.33% (LTO) and 7.68% (HTO) less than with the heavy oil alone). In addition, calculations of the effective rate constant confirmed the increased oxidation rate trend of both catalysts, with Mn-TO exhibiting the highest values. The findings highlight the potential of these manganese-based catalysts, the Mn-TO catalyst in particular, in optimizing heavy oil oxidation processes. The overall results further contribute to developing more efficient ligand catalyst complexes for sustainable heavy oil recovery while continuously improving their efficient application during in situ combustion in the petroleum industry.

Developmental Thermal Reaction Norms of Leatherback Marine Turtles at Nesting Beaches

Accurate scientific information is critical for undertaking appropriate conservation and management practices for imperiled species. One source of concern is that research findings might vary for non-biological reasons, including experimental design and analytical methods. To illustrate, we provide detailed modern analysis of reproductive data for leatherback turtles (Dermochelys coriacea). This species exhibits significant fluctuations in nesting densities across different regions, possibly driven by local rather than global factors. Key factors influencing these changes include hatching success and sex determination, both sensitive to incubation temperatures (e.g., lower temperatures yield more males, higher temperatures yield females). This study updates the understanding of temperature-dependent sex determination (TSD) in this species using Bayesian statistics. Growth rate data from the West Pacific and Northwest Atlantic populations show a similar, monotone increase with temperature, affirming the reliability of the models used. The analysis of TSD patterns indicates that observed differences are more likely due to study methodologies and clutch-specific factors rather than regional differences. These findings challenge previous assumptions, showing that leatherback TSD does not conform to a simple on/off pattern but is influenced by multiple, interacting environmental factors. Population dynamics models must account for these complexities, recognizing that both sex ratios and hatching success are critical to understand the rapid changes observed in some leatherback populations.

Numerical Simulation of MHD Oldroyd-B Fluid with Thermal Radiation and Chemical Reactions Using Chebyshev Wavelets

The study has been carried out to analyze the Magnetohydrodynamic (MHD) boundary layer flow, heat and mass transfer of the two-dimensional viscoelastic Oldroyd-B fluid over a vertical stretching sheet in the presence of thermal radiation and chemical reaction with suction/injection in a steady state. The governing equations of the system are partial differential equations, which then give rise to a set of highly nonlinear coupled ordinary differential equations using similarity transformations. The nonlinearity in the differential equations is dealt with quasilinearization technique. The resultant equations are numerically solved using Chebyshev wavelet collocation method. The effects of magnetic field, radiation, chemical reaction and buoyancy parameters are investigated. The numerical values of local skin friction coefficient, local Nusselt number and local Sherwood number are also tabulated and analyzed. We observe that the increase in buoyancy parameters enhances the velocity profiles and larger values of magnetic field decrease the velocity profiles but increases the temperature and concentration profiles. Error analysis has been done to check the convergence of the numerical scheme.

Photoinduced Transformations with Diverse Maleimide Scaffolds

Maleimides serve as crucial components in various synthetic processes and are of significant interest to researchers in bioorganic chemistry and biotechnology. Although thermal reactions involving maleimides have been studied extensively, light-mediated reactions with maleimides remain relatively underutilized. This review focuses on understanding the behavior of maleimides in their excited state, particularly their role as synthetic scaffolds for excited-state reactions. Specific emphasis is placed on the diverse photoreactions involving maleimides and photophysical evaluation from our research group.

Use of In-Situ ESR Measurements for Mechanistic Studies of Free Radical Non-Catalytic Thermal Reactions of Various Unconventional Oil Resources and Biomass

The exhaustion of conventional light oils necessitates the shift towards unconventional sources such as biomass, heavy oil, oil shale, and coal. Non-catalytic thermal cracking by a free radical mechanism is at the heart of the upgrading, prior to refining into valuable products. However, thermal pyrolysis is hindered by the formation of asphaltenes, precursors to coke, limiting cracking, causing equipment fouling, and reducing product stability. Free radicals are inherently present in heavy fractions and are generated during thermal processes. This makes these reactive intermediates central to understanding these mechanisms and limiting coking. Electron spin resonance (ESR) spectroscopy facilitates such mechanistic studies. Over the past decade, there has been no review of using in-situ ESR for studying thermal processes. This work begins with a brief description of free radicals’ chain reactions during thermal reactions and the wealth of information ESR provides. We then critically review the literature that uses ESR for mechanistic studies in thermal pyrolysis of biomass, heavy oil, shales, and coal. We conclude that limited literature exist, and more investigations are necessary. The key findings from existing literature are summarized to know the current state of knowledge. We also explicitly highlight the research gaps.

Photoinduced Self-assembly: An Alternative Strategy for the Construction of Coordination Oligomers and Polymers.

Self-assembled oligonuclear and polynuclear complexes have numerous functionalities and potential applications. Generally, such compounds have been constructed by thermal substitution reactions with bridging ligands. Herein, we report bottom-up and photochemical construction of functional coordination oligomers and polymers by photosubstitution-induced self-assembly. The photosubstitution reactions of a ruthenium precursor complex with bridging ligands having pyrazole moieties afford mono-, di-, tri-, tetra-, and pentanuclear ruthenium complexes, Ru1-Ru5, which have one-dimensional architectures. Intramolecular hydrogen bonding between each bridging ligand is a key to construct the molecular nanowires. All the complexes have been isolated and thoroughly characterized. The photochemically synthesized ruthenium complexes act as synthons for longer metal-complex-based nanowires with a length of the order of tens-of nanometers. The multinuclear complexes are generated by photoinduced self-assembly in the presence of a base, and they undergo photoinduced disassembly in the presence of acid.

Effects of SiO2-coated CNTs on the directional formation of SiC whiskers and improvement in the ablative resistance of polymer-matrix composites

As the development of hypersonic aerospace technology progresses, greater challenges are presented for solid rocket motors (SRMs) thermal protection, and the ablation performance of insulation materials needs to be further improved. Carbon nanotubes (CNTs) as a new type of reinforcing nano-filler, readily react with the oxidative components in the working gas during SRMs operation, limiting their excellent performance. In this study, we propose to coat the commonly used reinforcing filler, SiO2, on the surface of CNTs to suppress their susceptibility to oxidation and investigate the effects of adding CNTs, SiO2, and CNTs@SiO2 to the matrix on material properties. The results show that the addition of CNTs@SiO2 significantly improves the ablation resistance of the insulation material, with the linear ablation rate of M-@SiO2-2 being 56 % lower than that of M-SiO2-2. Based on the analysis of the material's antioxidation performance and the strength of the resulting char layer after ablation, the reasons for the improvement of ablation performance are discussed. By conducting high-temperature tube furnace tests, the composition and structure of the char layer at different temperatures are studied, and it is found that CNTs in the CNTs@SiO2 formulation can directly provide the carbon source required for the carbon thermal reduction reaction, promoting the directional growth of SiC whiskers. Based on these findings, an ablation mechanism is proposed.

Tumor Microenvironment-Responsive Zn(II)-Porphyrin Nanotheranostics for Targeted Sonodynamic Therapy.

As a novel noninvasive tumor therapy, sonodynamic therapy (SDT) attracts booming concerns. However, the limited water solubility, inadequate biocompatibility, and low targeting ability of conventional sonosensitizers significantly hinder their potential for clinical application. Herein, novel zinc(II)-porphyrin nanotheranostics (HA@Zn-TCPP) were fabricated in which the zinc(II)-porphyrin (TCPP) metal-organic framework was first constructed by a simple thermal reaction, followed by the addition of hyaluronic acid (HA) for modification. The specific targeting ability of HA facilitated the internalization of HA@Zn-TCPP within tumor cells, resulting in its preferential accumulation in tumor tissues that exhibit CD44 receptor overexpression. The acidic tumor microenvironment induced the rapid decomposition of HA@Zn-TCPP, releasing free TCPP for activating SDT. This controllable generation of reactive oxygen species (ROS) could effectively decrease damage to normal tissues. The HA@Zn-TCPP exhibited remarkable antitumor effects in experiments, achieving a tumor inhibition rate of up to 82.1% when under ultrasound. This finding provides an imperative strategy to develop novel sonosensitizers for enhanced SDT.

Preparation and flavor characteristics of plant-based meat flavoring by mixed fermentation of multiple strains

In this study, plant-based meat flavoring was prepared by mixed fermentation and thermal reaction. Based on the changes of amino acid nitrogen, reducing sugar, and total acid during the fermentation process and combined with sensory evaluation, the optimal fermentation conditions were determined as 4 % total inoculation amount of Monascus purpureus, Actinomucor elegans, and Bacillus subtilis with an inoculation ratio of 1:1:1, and 36 h of fermentation time. The odor characterization of meat flavoring was identified by solid-phase microextraction–gas chromatography–mass spectrometry (SPME–GC–MS), aroma extract dilution analysis (AEDA), quantitative measurements, odor activity value (OAV) and aroma recombination and omission experiments. 64 volatile compounds and 28 odorants were identified. The compounds with FD ≥ 27 were precisely quantified by five-point standard calibration curve and OAVs were calculated, and those with OAV ≥ 1 were subjected to aroma recombination and omission experiments. Finally, furfuryl mercaptan, difurfuryl disulfide, 4-methyl-5-ethylthiazole, 1-octanal, and 2-acetylthiophene were determined to be the key aroma-active compounds. These compounds have been recognized as key aroma-active compounds or detected in other meats or meat flavorings. In this study, we prepared plant-based meat flavoring through mixed fermentation, and provide new ideas for the development of plant-based thermal reaction meat flavoring process.

Recycling of flotation residual carbon from coal gasification fine slag through thermal combustion reaction: Insight into the spatial and temporal multi-scale evolution of typical heavy metals

The necessity for a fundamental comprehension of the migration and transformation patterns of heavy metals in the combustion reaction process is paramount to ensure the effective and targeted prevention and control of heavy metal pollution in the context of large-scale energy utilization of waste coal gasification fine slag. This study aims to reveal the fate of typical heavy metals during the combustion reaction of coal gasification fine slag to provide valuable insight for its clean secondary use. In this work, the thermal combustion reactivity of coal gasification fine slag was initially enhanced through froth flotation, and then the spatial and temporal multi-scale evolution of heavy metals in the flotation carbon-rich fraction was investigated by a series of analytical experiments. The results demonstrate a strong correlation between the volatility of typical heavy metals and the combustion reaction process of the flotation carbon-rich fraction. The volatility of V, Ni, Cu, Zn, and Pb is consistently high, of which the volatility of Zn and Pb is consistently above 50%, while the volatility of Cr, Mn, and Ba exhibits greater temperature sensitivity. As the reaction proceeds, the specific surface area of the solid residue expands, and then the smooth and dense mineral particles dissolve into each other to form a cluster structure simultaneously with the collapse of the pore structure, resulting in the volatility of the heavy metals firstly increasing and then decreasing. Furthermore, alkali metals and alkaline earth metal compounds are effective carriers of Cr, Mn, and Ba in the bottom residual. Additionally, the type and number of crystalline minerals in the bottom residual gradually increase as the reaction progresses. This results in the gradual conversion of the heavy metals bound to unstable carbonate minerals and sulphones into more stable chemical forms. The findings provide novel theoretical support and technical guidance for the environmentally sound and efficient utilization of residual carbon in the waste coal gasification fine slag.

Thermal reaction based mesoscale ablation model for phase degradation and pyrolysis of needle-punched composite

Needle-punched composites are highly valued for their exceptional resistance to interlaminar properties, ablation, and design flexibility, making them increasingly popular in aerospace thermal protection systems. This work investigates the mesoscale structural characteristics and thermophysical properties of needle-punched composites in ablation process. Oxyacetylene ablation experiments were carried out at different temperatures, and a mesoscopic needle-punched structure model was established based on the results of CT characterization. Further, Abaqus custom subroutine was used to reveal the ablation evolution mechanism of carbon fiber reinforced phenolic resin-based needle-punched composites. The results show that, at mesoscopic scale, the acicular fiber bundle perpendicular to the ablative surface accelerates the heat conduction to the interior of the material and promotes the thermal damage and performance degradation of the composite.

State-of-the-Art Light-Driven Hydrogen Generation from Formic Acid and Utilization in Enzymatic Hydrogenations.

A concept of combining photocatalytically generated hydrogen with green enzymatic reductions is demonstrated. The developed photocatalytic formic acid (FA) dehydrogenation setup based on Pt(x)@TiO2 shows unprecedented hydrogen generation activity, which is two orders of magnitude higher than reported values of state-of-the-art systems. Mechanistic studies confirm that hydrogen generation proceeds via a photocatalytic pathway, which is entirely different from purely thermal reaction mechanisms previously reported. The viability of the presented approach is demonstrated by the synthesis of value-added compounds 3-phenylpropanal and (2R, 5S)-dihydrocarvone at ambient pressure and room temperature, which should be applicable for many other hydrogenation processes, e.g., for the preparation of flavours and fragrance compounds, as well as pharmaceuticals.

The influence of a non-uniform heat source/sink and Joule heating on the convective motion of a micropolar fluid in a chemically radiative MHD medium across a stretched sheet

The objective of the present exploration is to examine impactions of radiation, a non-uniform intensity source, and a permeable medium on a temperamental MHD blended convective micropolar liquid over an extended sheet subject to Joule heating. To transform the formulated problem into ordinary differential equations, the applicable similarity transformation is implemented. By utilizing R-K-F 4th -5th order approach with shooting method with MATLAB, the numerical solution is obtained. For the relevant profiles, the dimensionless parameters are visually displayed and described. Skin friction, the Nusselt number, and the Sherwood number have all been calculated using the answer found for the velocity, temperature, and concentration. With the assistance of line graphs, the impact of different flow factors being introduced into the problem is addressed. This research is conducted on the implications of MHD, porous, thermal radiation, viscous dissipation, Joule heating, non-liner thermal radiation and chemical reaction. For large values of micropolar parameter, the temperature is reduced and velocity and angular momentum distributions are raised. With the thermal radiation parameter, the temperature distribution gets better and thermal boundary layer is improved while the large values of Eckert number and non-uniform heat source or sink parameters, thermal boundary layer is improved. The higher thermal conductivity is proportional to the thickness of the thermal boundary layer. The concentration profile degrades with higher Schmidt number and chemical reaction parameter values. The current examination pertains to the significant subject matter of cooling of systems, artificial heart identification, oil-pipelined frictions, flow-tracers.

A thermal performance study on magnetic dipole based viscoplastic nanomaterial deploying distinct rheological aspects

Magnetic nanoliquids stand inimitable when compared with conventional liquids as their distinctive magnetic attributes can be regulated utilizing magnetic fields. For this reason, heat transference can be stimulated or regulated subjected to externally imposed magnetic fields. Magnetic nanoliquids are useful in comparison to orthodox or non-magnetic nanoliquids. These encompasses, energy conversion, electronics, hydraulics, thermal engineering and bioengineering. This study elaborates the magnetic dipole impact on convectively heated rheological nanomaterial confined by stretchy surface. Mathematical modeling is based on thermally radiative viscoplastic (Casson) model. Porous medium features are scrutinized through Darcian Forchheimer (DF) relation. Two-component Buongiorno nanomaterial model which captures Brownian diffusive together with thermophoretic diffusion is under consideration. Energy and solutal transportation expressions capture thermal source and chemical reaction effects. The dimensionalized nanomaterial flow model for stretching flow is obtained by deploying similarity variables. Numerical solutions are computed through Bvp4c scheme. The physical outcomes are elucidated graphically and arithmetically on dimensionless quantities (i.e., Nusselt number, temperature, skin-friction, velocity, Sherwood number and concentration streams). A benchmark is reported to authenticate the acquired numeric solutions. It is further visualized that nanomaterial temperature escalates subject to higher estimations of thermal Biot number, Curie temperature factor, radiation factor, thermophoresis parameter, heat source, ferrohydrodynamic interaction factor and Brownian diffusive parameter while it diminishes with Prandtl number and dissipation factor.

Photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2H)-ones containing a terpyridine receptor

New photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophen-3(2H)-ones containing a terpyridine receptor have been synthesized. They absorb in the visible region of the spectrum at 423–426 nm and exhibit emission at 463–468 nm. Their irradiation in acetonitrile with light of 436 nm leads to a multi-stage rearrangement, including Z/E isomerization about the CC bond, N → O migration of the acyl group and the formation of non-emissive O-acylated E-isomers, which were isolated preparatively. Their structure was established unambiguously by IR, 1H, 13C NMR spectroscopy and HR mass spectrometry. The reverse thermal reaction with O → N migration of the acyl group is catalyzed by acid catalysts. N-Acylated compounds in acetonitrile selectively form non-fluorescent complexes with Fe2+ cations, which is accompanied by the naked-eye effect with changing the color from yellow to maroon. A successful selective interaction with AcO− led to the restoration of the initial absorption and emission properties. Density functional theory (DFT)calculations at the M06-2X/def2-TZVP level with the PCM solvation method were used to explain the observed photoisomerizations and ionochromic transformations. The obtained compounds represent multifunctional on-off-on molecular switches of optical and fluorescent properties upon sequential exposure to light and H+ or sequential addition of Fe2+ and AcO− ions. A combinatorial logic gate was designed based on the basis of these switching properties.

Efficiency analysis of solar radiation on chemical radioactive nanofluid flow over a porous surface with magnetic field

Artificial neural networks have revolutionized machine learning by providing exceptional capabilities for modeling complicated mechanisms and solving various challenges. Backpropagation is an important training technique in the field of artificial neural networks. However, this technique must be optimized when working with complicated fluid dynamics. This study analyzes the three-dimensional radiative flow of a tangent hyperbolic fluid driven by the Cattaneo-Christov flux system across a porous stretching sheet using ANN backpropagation enhanced by Bayesian Regularization approach. Heat and mass transfer analysis includes thermal radiation, chemical reactions and Cattaneo-Christov flux model. Porosity, radiation, chemical reaction rate, and ion slip effect are among the important physical characteristics that are modified to see how they affect fluid dynamics. Using MATLAB's BVP4C solver, the velocity, temperature, and concentration profiles that result from these model equations provide the training dataset for ANNs. The dataset is divided into 80 % for training, 10 % for testing, and 10 % for validation. Performance plots, regression graphs, and error histograms are used to analyze the performance of the LMT-based ANN and demonstrate its high accuracy and efficiency. With an R2 value of 1, the ANN produced a mean squared error of around 10⁻11. Fluid mobility drops as the magnetic parameter grows, while the thermal profile exhibits an increasing trend. Similarly, decreasing fluid velocity is the outcome of raising the porosity parameter. The study's conclusions have great potential for use in sectors that need sophisticated cooling and heating equipment.

Hygroscopic effects on sound absorption of multiscale bio-based porous materials

Hygroscopicity is the tendency of a material to absorb moisture from the surrounding environment. This work investigates hygroscopic effects on the sound absorption properties of multiscale bio-based materials. It is shown how moisture can significantly alter their acoustic performance as well as how to recover their original dry-material performance by means of heat treatment, akin to thermal reactivation commonly used in the chemical engineering industry. The results of an experimental campaign, conducted over an extended period of time, is reported. Possible theoretical explanations on the reduced acoustic performance of activated carbons by hygroscopic effects and the achieved improvement, obtained after heat treating the material, are also presented. The results of this work provide useful insights on the long-term acoustic behaviour of multiscale bio-based materials for noise control applications.