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When working with, and learning about, the thermal balance of a chemical reaction, we need to consider two overlapping but conceptually distinct aspects: one relates to the process of reallocating entropy between reactants and products (because of different specific entropies of the new substances compared to those of the old), and the other to dissipative processes. Together, they determine how much entropy is exchanged between the chemicals and their environment (i.e., in heating and cooling). By making explicit use of (a) the two conjugate pairs chemical amount (i.e., amount of substance) and chemical potential, and entropy and temperature, respectively, (b) the laws of balance of amount of substance on the one hand and entropy on the other, and (c) a generalized approach to the energy principle, it is possible to create both imaginative and formal conceptual tools for modeling thermal balances associated with chemical transformations in general and exothermic and endothermic reactions in particular. In this paper, we outline the concepts and relations needed for a direct approach to chemical and thermal dynamics, create a model of exothermic and endothermic reactions, including numerical examples, and discuss how to relate the direct entropic approach to traditional models of these phenomena.

In this study, oyster shells were processed and classified into sizes equal to or smaller than the fine aggregate threshold, and their engineering properties and fire-resistant performance were examined. The differences in heating weight loss of oyster shell aggregate (OSAs) with different particle sizes were examined using thermogravimetric analysis (TGA). The TGA results showed indicating that the temperature at which decarboxylation reaction started depended on the OSA particle size. The porosity of mortar specimens was analyzed using mercury intrusion porosimetry (MIP). The porosity area and porosity of the OSA-containing mortar increased with decreasing particle size. Mortar fire-resistant boards with heated for 2 h in accordance with the heating conditions of KS F 2257-1(methods of fire-resistant testing for structural element—general requirements) to measure their back-side temperature. The board made with OSA2.5 exhibited 273.2 °C, which is more than 90 °C higher than the back-side temperature of the board with OSA 0.6Under. Such difference was attributed to the greater heat transfer delay caused by higher porosity, porosity area, and specific surface area in OSAs with small particle sizes. The TGA results combined with the heating test results suggested that CO2 would be generated at different temperatures in boards containing OSAs with different particle sizes because of the differences in the endothermic reaction temperature.

The impact of the Thompson and Troian slip restrictions on continuous nanofluid flow, including CNTs near the stagnation point with constricting/enlarging surfaces, examined using a mathematical model. Engine oil is utilized as the base liquid, and both single-wall (SWCNTs) and multi-wall (MWCNTs) carbon nanotubes are taken into consideration. A Darcy-Forchheimer permeable medium and quartic autocatalysis, a chemical reaction for MHD stagnation point flow, are used to study the heat and flow characteristics of non-Newtonian flow. The original mathematical model is also expanded to include the impact of buoyancy forces. The numerical solution of non-dimensional velocity, temperature, and concentration profiles is obtained using the MATLAB-created bvp4c function, which employs the three-stage Lobatto IIIa formula. In the limited case, the validity of the recommended mathematical model is assessed by comparison with published work. A strong consensus is reached in this regard. Many dimensionless flow parameters, including the velocity slip parameter, the inertial coefficient, solid volume fraction, magnetic parameter, and the velocity parameter, have graphical representations that illustrate their behavior. Surface drag force estimates are presented to analyze the consequences on the extended surface. It has been demonstrated that increasing the slip velocity parameter boosts fluid flow speed while reducing surface drag. The efficiency of local thermal transmission decreases as the endothermic/exothermic coefficient rises. The altering viscosity factor for nanofluids causes an increase in axial velocity while a decrease in temperature distribution. Engine oil enriched with MWCNT and SWCNT can improve the thermal conductivity and viscosity of lubricants, leading to reduce wear and tear and better engine performance as well. Furthermore the incorporation of quartic autocatalytic reactions can enhance chemical processes that rely on catalysis, improving reaction rates. Also it has diverse applications in the system of cooling devices, manufacturing and material processing and heat transfer systems. It is revealed through this study that the system is shown to moderately cool off as measured by the solid volume ratio and heat generation. The velocity ratio parameter and the thermal expansion parameter had opposing outcomes on the system’s internal heat transfer mechanism.Article HighlightsAs we increase the volume fraction of nanoparticles, the velocity of the fluid diminishes while temperature profile exhibits enlargement.Temperature of the fluid flow portrays the fall off pattern for the enhanced values of thermal relaxation time.An enhancement in the exothermic and endothermic factor shows lowering the concentration profile.

This study presents a methodology and its results for predicting transport properties using two TRAPP methods, adopting CH 4 and C 3 H 8 as the reference fluids, over a wide range of temperature and pressure conditions, including both subcritical and supercritical regions. When hydrocarbon aviation fuels circulate in the regenerative cooling system of a hypersonic flight vehicle, endothermic reactions take place and reaction products are created. Here the viscosity and thermal conductivity of representative fuels and some of their products are predicted in the range of temperatures from 400 to 1000 K and pressures from 0.1 to 5.0 MPa. The results are then compared with data from the NIST database in terms of relative deviation. The TRAPP methods are found to be capable of predicting the viscosity and the thermal conductivity of both light and heavy hydrocarbons and their mixtures over a large range of liquid, gas, and supercritical regions. The relative deviations, however, tend to be considerably larger for higher molecular weight hydrocarbons, because the prediction performance for the liquid state is worse than that for the gaseous and supercritical states. It is also observed that the accuracy of the prediction of viscosity by the methane-based TRAPP (m-TRAPP) method is in general much better than that by the propane-based TRAPP (p-TRAPP) method, with an average relative deviation of within 22%. On the other hand, the p-TRAPP method offers excellent predictions of thermal conductivity in both the gas and the liquid regions, with an average relative deviation of within 14%. It would, therefore, be reasonable to use m-TRAPP for predicting the viscosity and p-TRAPP for the thermal conductivity of recirculating aviation fuels and the hydrocarbons produced by the fuels’ endothermic reactions.

Recently, there has been an increasing recognition of the crucial significance of waste management and the need for environmental preservation. Moreover, the impact of endothermic and exothermic reactions on heat transfer and the behavior of liquids on surfaces of variable thicknesses has significant implications for improving diverse operations, such as temperature exchange systems, commercial power plants, and waste administration facilities. In view of these applications, the current study investigates the endothermic and exothermic chemical reactions and waste discharge concentration over variable thickness surface. The governing equations are transformed into ordinary differential equations and solved using Runge–Kutta–Fehlberg 45 method. The results are visually presented using graphs and then analyzed. The results claim that the heat transfer rate is significant in the presence of wall thickness parameter and exothermic reaction. Elevated concentrations are observed when the external source parameter is augmented, and higher rate concentrations are commonly observed when the wall thickness parameter is present. This study explores the complex interaction of these responses and their consequences, providing insight into how they might be used to enhance these crucial processes. Further, it also focuses mainly on the concentration of waste discharge. It aims to provide significant insights into the impact of these processes on waste treatment operations, pollution control, and the effective disposal of industrial waste. The outcomes offer a strong basis for making well-informed decisions in companies and environmental sectors that rely on efficient waste management and sustainable practices.

The vacuum autocatalytic esterification process and reaction kinetics of pentaerythritol and octanoic acid at the reaction temperature of 220℃ to 250℃ were studied by online sampling method. The kinetic parameters of the stepwise esterification reaction were calculated, and the reaction kinetic model was established. The results show that the synthesis of pentaerythritol octanoate by vacuum autocatalytic esterification method requires no catalyst, the reaction time is 4-5 h, the esterification rate is more than 98%, and the content of tetraester is over 96%. The reaction is endothermic and the activation energy of each step is 23.21~32.26 kJ⋅mol −1 . The calculated kinetic model is in good agreement with the experimental values.

The gyrotactic microbe's addition to the nanofluid provides better thermal conductivity and increased heat transfer, in various systems like micro-mixers for bacteria, microbial fuel cells, and micro-volumes, such as microfluidic devices, biosensor enzymes, and micro-devices in a chip-shaped such as bio-microsystems. They are essential for effective thermal management in electronics, automotive, and aerospace sectors because of their special swirling motion, improving heat dissipation. This attempt discusses thermal issues, reduces energy usage, and greatly increases heat exchanger efficiency, all leading to more efficient and sustainable engineering solutions. Further, this article aims to investigate the incompressible flow of a viscous nanofluid and gyrotactic microbes around an elastic cylinder that swirls when positioned inside a porous medium. A constant directed magnetic field and a constant temperature at the border are considered. Activation energy, exponential heat source, and Joule heating are among the important heat sources that are considered. The production of entropy in a system is optimized. The modeled system of PDEs is converted into ODEs through appropriate variables. The ND-Solve scheme employed in Mathematica tool for numerical simulations to analyze the scientific questions, and plots illustrating how different physical parameters affect different distributions. The drag force, mass microbes, and heat transportations at the swirling cylinder surface are also examined in the form of numerical data. Finding obtained explores that bioconvection Lewis number enhance the entropy and Bejan number. Furthermore, reaction and activation energy variable enhancement show opposite impact on nanomaterial, concentration. Also, exothermic/ endothermic reaction, skin friction is invariant against. The results gained might be beneficial for many applications in science and engineering.

A mathematical model is created to analyze the impact of Thompson and Troian slip boundaries over a contracting/expanding surface sustaining nanofluid-containing carbon nanotubes along a stagnation point flow. Both multi-wall (MWCNTs) and single-wall (SWCNTs) carbon nanotubes are taken into consideration, with water serving as the base liquid. The flow is obtained due to the stretching or contracting of the surface. The thermal radiation, activation energy, buoyancy impacts, and chemical processes called quartic autocatalysis are additionally added to the original mathematical model. The MATLAB-constructed bvp4c function involving the three-stage Lobatto IIIa formula for the numerical results of dimensionless velocity, concentration, and temperature profiles are used. By contrasting it against a published paper in this limited instance, it is determined whether the suggested mathematical model is legitimate. In this sense, a remarkable consensus is achieved. Graphical representations are used to depict the behavior of many non-dimensional flow variables, such as the slip velocity parameter, the inertia coefficient, the porosity parameter, and the solid volume fraction. Surface drag force computations are reported to examine the effects at the permeable stretching surface. It has been shown that increasing the slip velocity factor increases the fluid streaming velocity while decreasing the surface drag force. If the endothermic/exothermic coefficient increases, the local thermal transfer efficiency falls. For nanofluids, the changing viscosity factor increases axial velocity while decreasing temperature distribution. Additionally, the solid volumetric fraction improves the temperature distributions by lowering the concentration profile and speed.

Inefficient thermal transmission in heat exchangers requires creative solutions. Ternary hybrid nanofluids have evolved to offer improved thermal efficiency compared to standard nanofluids. The current study involves a ternary hybrid nanofluid of copper oxide (CuO), titanium dioxide (TiO2), and silver (Ag) nanoparticles suspended in a base fluid of water-ethylene glycol (50–50%) (H2O–C2H6O2) to enhance thermal efficiency. This comprehensive analysis aims to provide insights into the heat transfer behaviour of a ternary hybrid nanofluid flow through a porous medium, considering the magnetic field effects in the momentum equation, exothermic/endothermic (Thermochemical) reactions in the energy equation, and activation energy in the concentration equation, respectively, on a rotating stretching sheet. Partial differential equations (PDEs) govern the flow problem. PDEs are converted to Ordinary differential equations (ODEs) using a suitable similarity transformation to aid solution. The linearised equations are solved numerically using MATLAB’s “bvp4c” boundary value problem solver. Variations in the velocity, temperature and concentration profiles due to various parameters are presented graphically. The results show that increasing M and Fr values increases profile by 1.2% and 0.85% respectively. Whereas the overall increase in the heat transfer is 6.65% and mass transfer is 1.86%, making this a substantial contribution to our work. This research will benefit manufacturers of cosmetics, hydraulic fluids, and fibreglass. Furthermore, the findings are supported by the available literature in specific instances, and they exhibit a strong concordance.

SignificanceCO2 is a greenhouse gas. Synthesis of liquid fuel using CO2 and H2 is promising for the sustainability of mankind. The reported technologies usually proceed via CO intermediate, which needs high temperature, and tend to cause low selectivity. Direct hydrogenation of CO2 to liquid fuel, not via CO, is a challenging issue. In this work, we designed a Co6/MnOx nanocatalyst that could successfully avoid the CO route. The reaction could proceed at 200 °C, which is much lower than those reported so far. The selectivity of the liquid fuel in total products reached 53.2 C-mol%, which is among the highest reported to date. Synthesis of liquid fuels (C5+ hydrocarbons) via CO2 hydrogenation is very promising. Hydrogenation of CO2 to liquid hydrocarbons usually proceeds through tandem catalysis of reverse water gas shift (RWGS) reaction to produce CO, and subsequent CO hydrogenation to hydrocarbons via Fischer–Tropsch synthesis (FTS). CO2 is a thermodynamically stable and chemically inert molecule, and RWGS reaction is endothermic and needs a higher temperature, whereas FTS reaction is exothermic and is thermodynamically favored at a lower temperature. Therefore, the reported technologies have some obvious drawbacks, such as high temperature, low selectivity, and use of complex catalysts. Herein we discovered that a simple Co6/MnOx nanocatalyst could efficiently catalyze CO2 hydrogenation. The reaction proceeded at 200 °C, which is much lower than those reported so far. The selectivity of liquid hydrocarbon (C5 to C26, mostly n-paraffin) in total product could reach 53.2 C-mol%, which is among the highest reported to date. Interestingly, CO was hardly detectable during the reaction. The in situ Fourier transform infrared characterization and 13CO labeling test confirmed that the reaction was not via CO, accounting for the eminent catalytic results. This report represents significant progress in CO2 chemistry and CO2 transformation.