Thermal Parameters Research Articles

Multiscale modeling and thermal conductivity evaluation of nano-reinforced composite materials with pore defect

The performance of resin-based composite materials often exhibits diversity due to the designability of various components. Thermal conductivity, an important thermal parameter of the composite, plays a significant role in thermal-chemical reactions, thermal stress analysis, temperature conduction, etc. However, it is relatively difficult to experimentally explore the thermal conduction mechanism of hybrid composite materials, mainly due to the relatively difficult control of various components. Therefore, this paper proposes a sequentially coupled cross-scale numerical method to characterize the thermal conductivity of nano-reinforced composite materials with pores by a multiscale periodic Representative Volume Element model generated by an improved Random Sequential Absorption algorithm. Firstly, periodic temperature boundary conditions are described, and the thermal conductivity performances of nano-reinforced matrix and composite with pores are investigated based on the finite element homogenization theory. Then, the proposed modes are validated and grid sensitivity analysis is conducted, indicating that the optimal grid sizes for the RVE models are 1.9 nm for the nano-reinforced matrix and 0.14 μm for the composite with pores based on a comprehensive comparison of four pore characterization methods, respectively. Furthermore, the study explored the effect of multiple parameters including nanoparticle content, pore content, and pore shape on thermal conductivity. Numerical findings reveal that the thermal conductivity of the nanocomposite matrix exhibits a linear increase with higher particle content. Specifically, compared to 0 % particle content, the thermal conductivity rises by 141.92 % at 12 % particle content. While the composite material's transverse thermal conductivity is sensitive to porosity content, it is less influenced by pore shape. The method proposed in this paper provides an effective approach for studying the thermal conduction of nano-reinforced composite materials with pores, and the research findings also offer theoretical guidance for process engineers.

Heat transfer innovation of engine oil conveying SWCNTs-MWCNTs-TiO2 nanoparticles embedded in a porous stretching cylinder

The influence of boundary layer flow of heat transfer analysis on hybrid nanofluid across an extended cylinder is the main focus of the current research. In addition, the impressions of magnetohydrodynamic, porous medium and thermal radiation are part of this investigation. Arrogate similarity variables are employed to transform the governing modelled partial differential equations into a couple of highly nonlinear ordinary differential equations. A numerical approach based on the BVP Midrich scheme in MAPLE solver is employed for solution of the set of resulting ordinary differential equations and obtained results are compared with existing literature. The effect of active important physical parameters like Magnetic Field, Porosity parameter, Eckert number, Prandtl number and thermal radiation parameters on dimensionless velocity and energy fields are employed via graphs and tables. The velocity profile decreased by about 65% when the magnetic field parameter values increases from 0.5 to 1.5. On the other hand increased by 70% on energy profile. The energy profile enhanced by about 62% when the Radiation parameter values increases from 1.0 < Rd < 3.0. The current model may be applicable in real life practical implications of employing Engine oil-SWCNTs-MWCNTs-TiO2 nanofluids on cylinders encompass enhanced heat transfer efficiency, and extended component lifespan, energy savings, and environmental benefits. This kind of theoretical analysis may be used in daily life applications, such as engineering and automobile industries.

Experimental and Theoretical Investigation of Thermal Parameters Influencing the Freezing Process of Ice Cream

Experimental and Theoretical Investigation of Thermal Parameters Influencing the Freezing Process of Ice Cream

Experimental study on improving the thermal performance of isobutane refrigeration system by parameter optimization

Improvement of thermal efficiency for isobutane refrigeration system could match well with the building requirements of low-carbon, and sustainable development. The electric radiant heater (ERH) is widely used for the freeze and cold storage (FCS) system, but it has problems of high electric consumption and high freezer compartment temperature rise (FCTR) as a result of low heat-transfer efficiency under defrosting. Therefore, a novel FCS system with an additional electric radiant heater (AERH) based on the heat required for frost melted and synchronous defrosting is proposed. The defrosting consumption and the FCTR of the novel FCS system are comprehensively evaluated by a novel evaluation method. Besides, the effect of the thermal parameters (i.e., the defrosting pause temperature, the position, and electric power of the AERH) on the heat transfer characteristics are compared and optimized by the experimental method. Finally, a novel method is presented to predict the optimum thermal conditions. The results show that the optimum system thermal performance is obtained, the defrosting duration and defrosting consumption are reduced by 44.02 % and 37.03 %, and the defrosting efficiency and energy efficiency could be increased by 17.92 % and 9.96 %, respectively, as compared to the conventional FCS system. The proposed FCS system has better economic performance and heat transfer efficiency. Meanwhile, 30.54 kg of CO2 emissions could be avoided during the annual operation period, and the environmental benefits are also considerable. This study not only reaffirms the benefit of using the AERH for defrosting in the FCS system but also provides a reference for the promotion and application of efficient heat transfer technology in building refrigeration engineering.

Optimizing heat pump unit selection for recirculating aquaculture workshops through computational fluid dynamics.

The selection of water temperature regulation equipment plays a crucial role in the design of workshops. At present, the choice of water temperature control equipment is usually based on the volume of the fish pond and thermal parameter calculation, combined with aquaculture experience. Empirical formulas only work in specific conditions due to factors like the environment, climate, and fish types,resulting in inaccurate equipment selection outcomes. Recognizing this limitation, this paper proposes to apply CFD simulation of the temperature field to accurately calculate the heat exchange value between indoor air and water, thereby predicting the heat exchange values during aquaculture activities in the aquaculture workshop. providing a new approach for equipment selection. This paper selects a puffer fish breeding workshop in Dalian as the simulation object, establishing a 3D unsteady-state Computational Fluid Dynamics model. The model considers outdoor temperature, solar radiation, and phase-change heat transfer in water. Comparison with experimental data reveals a root mean square error of 0.46°C for the simulated results. During summer, the highest cooling load occurs at 16:00, reaching 94.6 kW. It is recommended to employ the Daikin GCHP-40MAH ground source heat pump as the water temperature control equipment. CFD simulation validates its effectiveness in shaping the indoor temperature field post-installation. the investment in water temperature control equipment can be reduced to a certain degree. This provides a reference value for the selection of water temperature equipment in aquaculture workshops.

Sn99Ag0.3Cu0.7–TiO2 composite solder joints and their influence on thermal parameters of power components

Purpose This paper aims to investigate the influence of composite solder joint preparation on the thermal properties of metal-oxide-semiconductor field-effect transistors (MOSFETs) and the mechanical strength of the soldered joint. Design/methodology/approach Reinforced composite solder joints with the addition of titanium oxide nanopowder (TiO2) were prepared. The reference alloy was Sn99Ag0.3Cu0.7. Reinforced joints differed in the weight percentage of TiO2, ranging from 0.125 to 1.0 Wt.%. Two types of components were used for the tests. The resistor in the 0805 package was used for mechanical strength tests, where the component was soldered to the FR4 substrate. For thermal parameters measurements, a power element MOSFET in a TO-263 package was used, which was soldered to a metal core printed circuit board (PCB) substrate. Components were soldered in batch IR oven. Findings Shear tests showed that the addition of titanium oxide does not significantly increase the resistance of the solder joint to mechanical damage. Titanium oxide addition was shown to not considerably influence the soldered joint’s mechanical strength compared to reference samples when soldered in batch ovens. Thermal resistance Rthj-a of MOSFETs depends on TiO2 concentration in the composite solder joint reaching the minimum Rthj at 0.25 Wt.% of TiO2. Research limitations/implications Mechanical strength: TiO2 reinforcement shows minimal impact on mechanical strength, suggesting altered liquidus temperature and microstructure, requiring further investigation. Thermal performance: thermal parameters vary with TiO2 concentration, with optimal performance at 0.25 Wt.%. Experimental validation is crucial for practical application. Experimental confirmation: validation of optimal concentrations is essential for accurate assessment and real-world application. Soldering method influence: batch oven soldering may affect mechanical strength, necessitating exploration of alternative methods. Thermal vs mechanical enhancement: while TiO2 does not notably enhance mechanical strength, it improves thermal properties, highlighting the need for balanced design in power semiconductor assembly. Practical implications Incorporating TiO2 enhances thermal properties in power semiconductor assembly. Optimal concentration balancing thermal performance and mechanical strength must be determined experimentally. Batch oven soldering may influence mechanical strength, requiring evaluation of alternative techniques. TiO2 composite solder joints offer promise in power electronics for efficient heat dissipation. Microstructural analysis can optimize solder joint design and performance. Rigorous quality control during soldering ensures consistent thermal performance and mitigates negative effects on mechanical strength. Social implications The integration of TiO2 reinforcement in solder joints impacts thermal properties crucial for power semiconductor assembly. However, its influence on mechanical strength is limited, potentially affecting product reliability. Understanding these effects necessitates collaborative efforts between researchers and industry stakeholders to develop robust soldering techniques. Ensuring optimal TiO2 concentration through experimental validation is essential to maintain product integrity and safety standards. Additionally, dissemination of research findings and best practices can empower manufacturers to make informed decisions, fostering innovation and sustainability in electronic manufacturing processes. Ultimately, addressing these social implications promotes technological advancement while prioritizing consumer trust and product quality in the electronics industry. Originality/value The research shows the importance of the soldering technology used to assemble MOSFET devices.

Sn99Ag0.3Cu0.7–TiO2 composite solder joints and their influence on thermal parameters of power components

Purpose This paper aims to investigate the influence of composite solder joint preparation on the thermal properties of metal-oxide-semiconductor field-effect transistors (MOSFETs) and the mechanical strength of the soldered joint. Design/methodology/approach Reinforced composite solder joints with the addition of titanium oxide nanopowder (TiO2) were prepared. The reference alloy was Sn99Ag0.3Cu0.7. Reinforced joints differed in the weight percentage of TiO2, ranging from 0.125 to 1.0 Wt.%. Two types of components were used for the tests. The resistor in the 0805 package was used for mechanical strength tests, where the component was soldered to the FR4 substrate. For thermal parameters measurements, a power element MOSFET in a TO-263 package was used, which was soldered to a metal core printed circuit board (PCB) substrate. Components were soldered in batch IR oven. Findings Shear tests showed that the addition of titanium oxide does not significantly increase the resistance of the solder joint to mechanical damage. Titanium oxide addition was shown to not considerably influence the soldered joint’s mechanical strength compared to reference samples when soldered in batch ovens. Thermal resistance Rthj-a of MOSFETs depends on TiO2 concentration in the composite solder joint reaching the minimum Rthj at 0.25 Wt.% of TiO2. Research limitations/implications Mechanical strength: TiO2 reinforcement shows minimal impact on mechanical strength, suggesting altered liquidus temperature and microstructure, requiring further investigation. Thermal performance: thermal parameters vary with TiO2 concentration, with optimal performance at 0.25 Wt.%. Experimental validation is crucial for practical application. Experimental confirmation: validation of optimal concentrations is essential for accurate assessment and real-world application. Soldering method influence: batch oven soldering may affect mechanical strength, necessitating exploration of alternative methods. Thermal vs mechanical enhancement: while TiO2 does not notably enhance mechanical strength, it improves thermal properties, highlighting the need for balanced design in power semiconductor assembly. Practical implications Incorporating TiO2 enhances thermal properties in power semiconductor assembly. Optimal concentration balancing thermal performance and mechanical strength must be determined experimentally. Batch oven soldering may influence mechanical strength, requiring evaluation of alternative techniques. TiO2 composite solder joints offer promise in power electronics for efficient heat dissipation. Microstructural analysis can optimize solder joint design and performance. Rigorous quality control during soldering ensures consistent thermal performance and mitigates negative effects on mechanical strength. Social implications The integration of TiO2 reinforcement in solder joints impacts thermal properties crucial for power semiconductor assembly. However, its influence on mechanical strength is limited, potentially affecting product reliability. Understanding these effects necessitates collaborative efforts between researchers and industry stakeholders to develop robust soldering techniques. Ensuring optimal TiO2 concentration through experimental validation is essential to maintain product integrity and safety standards. Additionally, dissemination of research findings and best practices can empower manufacturers to make informed decisions, fostering innovation and sustainability in electronic manufacturing processes. Ultimately, addressing these social implications promotes technological advancement while prioritizing consumer trust and product quality in the electronics industry. Originality/value The research shows the importance of the soldering technology used to assemble MOSFET devices.

Mixed convective flow analysis of a Maxwell fluid with double diffusion theory on a vertically exponentially stretching surface

It observers that an object is submerged in a liquid, more pressure is applied to its bottom surface than its top surface, as a result pressure rises within depth of fluids. A buoyancy force is generated due to the pressure difference. In the current investigation, the mathematical formulation of bio-convective stagnation point flow of a radiative Maxwell fluid with multiple slip effect on an exponentially porous stretching surface is analyzed thoroughly. The buoyancy assisting and opposing conditions with magnetic field are discussed in the current investigation. Moreover, the energy and concertation equations are formulated by the utilization of Cattaneo–Christov theory and non-uniform heat source/sink. The flow model is developed in the form of partial derivatives, then use the similarity variables to convert the physical system into nonlinear ordinary derivative. The nonlinear system is tackled numerically with the help of Bvp4c approach on the MATLAB. The graphical upshots for various emerging parameter are observed with two aspects: buoyancy assisting λ>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda > 0} \\right)$$\\end{document} and buoyancy opposing λ<0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda < 0} \\right)$$\\end{document}. The observation shows that the greater values of mixed convection parameter improves the fluid velocity for assisting flow λ>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda > 0} \\right)$$\\end{document}, while declining trend is noticing for opposing flow situation λ>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda > 0} \\right)$$\\end{document}. Further, it is worth noticing that stronger inputs of thermal and concentration relaxation parameter yield lesser thermal and concentration diffusivity, which reduces the temperature and nanoparticles concentration.

Mixed convective flow analysis of a Maxwell fluid with double diffusion theory on a vertically exponentially stretching surface

It observers that an object is submerged in a liquid, more pressure is applied to its bottom surface than its top surface, as a result pressure rises within depth of fluids. A buoyancy force is generated due to the pressure difference. In the current investigation, the mathematical formulation of bio-convective stagnation point flow of a radiative Maxwell fluid with multiple slip effect on an exponentially porous stretching surface is analyzed thoroughly. The buoyancy assisting and opposing conditions with magnetic field are discussed in the current investigation. Moreover, the energy and concertation equations are formulated by the utilization of Cattaneo–Christov theory and non-uniform heat source/sink. The flow model is developed in the form of partial derivatives, then use the similarity variables to convert the physical system into nonlinear ordinary derivative. The nonlinear system is tackled numerically with the help of Bvp4c approach on the MATLAB. The graphical upshots for various emerging parameter are observed with two aspects: buoyancy assisting λ>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda > 0} \\right)$$\\end{document} and buoyancy opposing λ<0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda < 0} \\right)$$\\end{document}. The observation shows that the greater values of mixed convection parameter improves the fluid velocity for assisting flow λ>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda > 0} \\right)$$\\end{document}, while declining trend is noticing for opposing flow situation λ>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\lambda > 0} \\right)$$\\end{document}. Further, it is worth noticing that stronger inputs of thermal and concentration relaxation parameter yield lesser thermal and concentration diffusivity, which reduces the temperature and nanoparticles concentration.

Investigation of Magneto-convection in Viscoelastic Fluid Saturated Anisotropic Porous Layer Under Local Thermal Non-equilibrium Condition

The problem of magneto-convection in viscoelastic fluid saturated anisotropic porous layer under local thermal non-equilibrium (LTNE) effect is investigated. Extended Darcy model with time derivative term for viscoelastic fluid of the Oldroyd type with an externally imposed vertical magnetic field is used to model the momentum equation. The entire investigation has been split into two parts: (i) linear stability analysis (ii) weakly non-linear stability analysis. We perform normal mode technique to examine linear stability analysis while truncated representation of Fourier series method is used for weakly non-linear stability analysis. The onset of convection is set in through oscillatory rather than stationary mode due to competition between the processes of thermal, magnetic effect and viscoelasticity. A comparative study between anisotropic and isotropic porous medium is made as a function of Q (Chandrasekhar number), 𝛤 (non dimensional inter phase heat transfer coefficient), 𝜆1 (Relaxation time) and λ2 (Retardation time). Apart from this, Q, 𝛤 and λ2 stabilize the system in oscillatory case while 𝜆1 destabilize the system. Furthermore 𝜉 (mechanical anisotropic parameter), 𝜂s (thermal anisotropic parameter for solid phase), destabilizes the system and 𝜂f (thermal anisotropic parameter for fluid phase) stabilizes the system. The effect of Q, 𝜆1, λ2, 𝛤, 𝜉, 𝜂f and 𝜂s on heat transfer is also examined.

Investigation of Magneto-convection in Viscoelastic Fluid Saturated Anisotropic Porous Layer Under Local Thermal Non-equilibrium Condition

The problem of magneto-convection in viscoelastic fluid saturated anisotropic porous layer under local thermal non-equilibrium (LTNE) effect is investigated. Extended Darcy model with time derivative term for viscoelastic fluid of the Oldroyd type with an externally imposed vertical magnetic field is used to model the momentum equation. The entire investigation has been split into two parts: (i) linear stability analysis (ii) weakly non-linear stability analysis. We perform normal mode technique to examine linear stability analysis while truncated representation of Fourier series method is used for weakly non-linear stability analysis. The onset of convection is set in through oscillatory rather than stationary mode due to competition between the processes of thermal, magnetic effect and viscoelasticity. A comparative study between anisotropic and isotropic porous medium is made as a function of Q (Chandrasekhar number), 𝛤 (non dimensional inter phase heat transfer coefficient), 𝜆1 (Relaxation time) and λ2 (Retardation time). Apart from this, Q, 𝛤 and λ2 stabilize the system in oscillatory case while 𝜆1 destabilize the system. Furthermore 𝜉 (mechanical anisotropic parameter), 𝜂s (thermal anisotropic parameter for solid phase), destabilizes the system and 𝜂f (thermal anisotropic parameter for fluid phase) stabilizes the system. The effect of Q, 𝜆1, λ2, 𝛤, 𝜉, 𝜂f and 𝜂s on heat transfer is also examined.

Intelligent computing for the electro-osmotically modulated peristaltic pumping of blood-based nanofluid

The study delves into a novel application of artificial neural networks within the biomedical realm, specifically focusing on the peristaltic pumping of ionized blood-infused nanofluid using the Casson model. The investigation takes into account the impacts of electrokinetic forces, chemical reaction, thermal radiation and variable thermal conductivity. The endorsed nanofluid model encompasses both thermophoretic and Brownian diffusions. The Nernst-Planck and Poisson equations are used to characterize electroosmotic process. The mathematical model is then numerically solved using NDSolve in Mathematica. The variation in relevant hemodynamic characteristics concerning key flow parameters is explored through numerous graphical representations. Two distinct artificial neural networks have been developed to estimate values for rates of mass and heat transfer. The Levenberg-Marquardt algorithm is used as the training algorithm in network models with multi-layer perceptron architecture. Graphical inspection of the results demonstrates a decrease in blood flow with an elevated Helmholtz-Smoluchowski velocity. A lower pressure gradient is recorded with a higher electroosmotic parameter. Furthermore, an augmentation in the thermal conductivity parameter leads to a reduction in heat transfer rate at the wall. The concentration profile demonstrates an increase with a rise in the chemical reaction parameter. The results obtained from the neural network models exhibit an ideal harmony with the target values. The developed neural network models demonstrated the ability to predict rates of heat and mass transfer values with average deviations of −0.01% and 0.004%, respectively.

Suction influence on magneto-convective fluid flow embedded in a permeable media under internal friction

This work examines the natural convection flow of an incompressible, viscous, and electrically conducting fluid down a vertical flat plate in the presence of conduction, as well as the effects of suction, magnetic field, viscous dissipation, porous medium, and heat generation. The governing momentum and energy equations have numerical solutions. The impacts of suction, heat production, magnetic, porosity, and viscous dissipation parameters on two-dimensional flow are discussed. Graphical representations of the velocity profile, temperature distribution, skin friction, rate of heat transfer, and surface temperature distribution are shown. The presence of porous media and improving suction values improves the friction drag but diminishes the energy transfer. The thermal production parameter raises the energy inside the flow but diminishes the heat transfer coefficient. This work attempts to offer important insights into these intricate processes by examining the effects of controlling factors including magnetic fields, porous medium, and suction parameters. This research conclusion may find applications in coolers, heat exchangers, and environmental remediation technologies that are more effective, advancing engineering and sustainable practices.

Suction influence on magneto-convective fluid flow embedded in a permeable media under internal friction

This work examines the natural convection flow of an incompressible, viscous, and electrically conducting fluid down a vertical flat plate in the presence of conduction, as well as the effects of suction, magnetic field, viscous dissipation, porous medium, and heat generation. The governing momentum and energy equations have numerical solutions. The impacts of suction, heat production, magnetic, porosity, and viscous dissipation parameters on two-dimensional flow are discussed. Graphical representations of the velocity profile, temperature distribution, skin friction, rate of heat transfer, and surface temperature distribution are shown. The presence of porous media and improving suction values improves the friction drag but diminishes the energy transfer. The thermal production parameter raises the energy inside the flow but diminishes the heat transfer coefficient. This work attempts to offer important insights into these intricate processes by examining the effects of controlling factors including magnetic fields, porous medium, and suction parameters. This research conclusion may find applications in coolers, heat exchangers, and environmental remediation technologies that are more effective, advancing engineering and sustainable practices.

Experimental study on mechanical damage and creep characteristics of Gonghe granite under real-time high temperature

It is significant to study the mechanical properties of hot dry rock (HDR) for the development of deep geothermal energy. At present, the creep behavior of granite under real-time high temperature is not fully understood. The creep behavior of granite at 25 ∼ 800°C was investigated by real-time high-temperature uniaxial compression and graded load creep tests, and the thermal damage mechanism of granite was studied by scanning electron microscopy (SEM) experiments. The paper systematically analyzes the evolution of mechanical indexes such as uniaxial compressive strength (UCS), elastic modulus, creep deformation, steady creep rate and long-term strength of granite under thermal-force coupling. The results show that the UCS and elastic modulus of granite increase with increasing temperature in the range of 25 ∼ 200 °C, and decrease with increasing temperature in the range of 200 ∼ 800 °C. The damage speed of granite is the fastest in the temperature range of 400 ∼ 600 °C. The steady creep rate of granite increases with the increase of temperature and stress level. The ratio of long-term strength to UCS decreases with increasing temperature, from 93.6% at 25 °C to 73.2% at 800 °C. The research results provide relevant thermal damage mechanical parameters and theoretical basis for the development of HDR.

Thermal analysis of the HTS transformer in the fault current condition considering the tape roughness effect

High temperature superconducting (HTS) transformers have many advantages over conventional transformers in terms of volume, weight, and total efficiency. However, fault conditions limit the electro-thermal performance of an HTS transformer. Based on this, we investigate the thermal modeling of the HTS transformer in the fault-current state. For thermal modeling, heat transfer and parameters affecting it such as surface roughness and bubble behavior have been considered. At first, an accurate thermal model for a 10 kVA HTS transformer has been prepared. Experimental results show that the penalty of this model is about 2.5 K in the hot-spot point (HSP) temperature in fault-current conditions. In a second step, the impact of a roughness on the heat transfer and mass transfer rate in nucleated boiling mode is investigated. Results show that surface roughness decreases the HSP temperature by more than 10 K in fault-current conditions. These results have significant impacts on protecting HTS windings against quenching.

ANALYSIS OF METHODS OF ETHANE PIPELINE TRANSPORTATION

The products of hydrocarbon light fractions processing are becoming of great demand. An important component of natural gas is ethane used for high-tech products at gas chemical complexes. Ethane production in situ is a promising direction, with its subsequent transportation to gas and chemical plants. The most economical type of transport is pipeline transportation, providing the construction of a pipeline system including facilities and a linear part. Ethane is a gas that can be transported along isothermal pipelines in both liquid and gaseous states. At the same time, the question of choosing the most rational variant is relevant. The article analyzes possible methods of transporting ethane and ethane fractions along pipelines, consideres variants for pumping gas in a liquid and gaseous states, taking into account the component composition of the product at a specified productivity and initial thermal parameters to summarize recommendations when choosing the most rational method of product transportation. A method is presented for the analytical representation of the dependences of pressure, elasticity, density and viscosity on temperature for the convenient determination of physical properties of multicomponent ethane fractions. The methodological foundations of the thermal and hydraulic analysis of variants for ethane transportation in two phase states – in liquid and gaseous – with the energy efficiency assessment of gas pumping are presented. It is shown that when transporting ethane in a gaseous state, the metal consumption for the pipeline increases twice as compared with the pipeline for transporting the product in a liquid state, while energy consumption also doubles.

Insights into the oxidative thermal stability of mesoporous triazine‐based organic polymers: Kinetics and thermodynamic parameters

AbstractThis study investigates the thermal degradation kinetics of mesoporous triazine‐based polymers, namely triazine‐amine and triazine‐ether polymers. The synthesis, physicochemical characterization, and catalytic applications of these polymers were discussed in our previous report. Herein, the thermal stability parameters, including kinetic triplets and thermodynamic parameters, were determined using thermogravimetric analysis (TGA) and non‐isothermal mathematical approximations such as Coats‐Redfern, Broido, and Horowitz–Metzger methods. Triazine‐ether polymers exhibit thermal stability within the range of 200°C–300°C, while triazine‐amine polymer demonstrates superior thermal stability, reaching up to 450°C. According to the Coats‐Redfern method, the degradation follows reaction orders of 0.5 ≤ n ≤ 1. The activation energy of triazine‐amine polymer is notably high, particularly at the third degradation stage (e.g., 89.0 kJ/mol by the Broido method), attributed to its high nitrogen content. Conversely, the higher carbon content of triazine‐ether polymers reduces their activation energy to approximately 30 kJ/mol at all stages and thus, facilitates the degradation process. Thermodynamically, the degradation process is favorable yet non‐spontaneous, with intermediate states of the polymers exhibiting higher entropy, indicative of their enhanced degradation capability.

A Review of In-Flight Thermal Comfort and Air Quality Status in Civil Aircraft Cabin Environments

The civil aircraft cabin is enclosed and highly occupied, making it susceptible to a decline in indoor environmental quality. The environmental quality of civil aircraft cabins not only depends on objective factors such as temperature, relative humidity, and the presence of air pollutants such as carbon dioxide (CO2), carbon monoxide (CO), ozone (O3), particle matter (PM), and volatile organic compounds (VOCs) but also the subjective factors pertaining to the perceptions and health symptoms of passengers and crew. However, few studies have thoroughly examined the air quality and thermal comfort parameters that are measured during in-flight testing in airplane cabins, as well as the passengers’ subjective perceptions. In order to evaluate the in-flight thermal comfort and air quality status, this study conducted a review of the recent literature to compile data on primary categories, standard limits, and distribution ranges of in-flight environmental factors within civil aircraft cabins. Following a search procedure outlined in this paper, 54 papers were selected for inclusion. Utilizing the Monte Carlo method, the Predicted Mean Vote (PMV) distributions under different exercise intensities and clothing thermal resistance were measured with the in-cabin temperature and humidity from in-flight tests. Recommendations based on first-hand data were made to maintain the relative humidity in the cabin below 40%, ensure wind speed remains within the range of 0–1 m/s, and regulate the temperature between 25–27 °C (for summer) and 22–27 °C (for winter). The current estimated cabin air supply rate generally complies with the requirements of international standards. Additionally, potential carcinogenic and non-carcinogenic risks associated with formaldehyde, benzene, tetrachloroethylene, and naphthalene were calculated. The sorted data of in-flight tests and the evaluation of the subjective perception of the occupants provide an evaluation of current cabin thermal comfort and air quality status, which can serve as a reference for optimizing indoor environmental quality in future generations of civil aircraft cabins.

Exploration of the effects of anisotropy and rotation on Rayleigh–Bénard convection of nanoliquid-saturated porous medium using general boundary conditions

This paper presents an analysis of Rayleigh–Bénard convection (RBC) of a Newtonian-nanoliquid-saturated anisotropic porous medium in the presence of rotation (Rayleigh–Bénard–Taylor convection). The investigation is performed using non-classical boundary conditions. The effect of various parameters on the onset of convection is presented graphically. The system sees stabilisation due to an increase in the rotation rate and thermal anisotropy parameter whereas the system destabilises due to an increase in the mechanical anisotropy parameter. The results of 82 limiting cases can be extracted from the current work. The results of free-free, rigid-free and rigid-rigid isothermal/adiabatic boundaries are obtained from the present study by considering appropriate limits. The results of the limiting cases of the present study are in excellent agreement with those observed in earlier investigations.