Thermal Influences Research Articles

Thermal and magnetic influences on the hybrid nanofluid flow over exponentially elongating/contracting curved surfaces in porous media: a comprehensive study

Thermal and magnetic influences on the hybrid nanofluid flow over exponentially elongating/contracting curved surfaces in porous media: a comprehensive study

Thermodynamic Calculations of the Main Characteristics of the Combustion Process of Pyrotechnic Nitrate-Metallized Mixtures with Additives of Organic and Inorganic Substances under External Thermal Influences

The aim of the article is to determine the dependencies of the combustion product temperatures of four-component mixtures, the content of high-temperature condensate, and unoxidized metal on the excess oxidizer coefficient, the number of additives, and external pressure using thermodynamic calculations. Modern methods of physicochemical analysis (such as cinephotography and microcinephotography methods, X-ray analysis methods, non-contact and contact temperature measurement methods), nonlinear thermal conductivity and thermal stability methods, as well as mathematical and experimental-statistical modeling, were employed to investigate the influence of elevated heating temperatures (up to 800 K) and external pressures (up to 107 Pa) on the ignition and combustion processes of pyrotechnic products. Standard pyrotechnic equipment was used to test pyrotechnic product samples under specified conditions. Calculations based on models were conducted in real-time and dialog mode on computer devices that meet modern requirements for the use of specialized software. The results of thermodynamic calculations are presented for the dependencies of combustion product temperatures of multicomponent pyrotechnic mixtures based on powders of metal fuels (magnesium, aluminium), nitrate oxidizer (sodium nitrate), additives of organic and inorganic substances (paraffin, sodium fluoride), and the content of high-temperature condensate and unoxidized metal depending on the excess oxidizer coefficient α = 0.1…4.0, the amount of paraffin additive εp = 0…0.2, sodium fluoride additive εf = 0…0.06, and external pressure P = 105…107 Pa. Based on the obtained results of thermodynamic calculations, statistical models in the form of regression dependencies of the specified combustion characteristics on their technological parameters and external conditions have been developed. These models enable the determination of fire hazardous properties of mixtures in real-time dialog and PC-based scenarios, considering premature initiation of products based on them under external thermal actions.

Accelerated formation of M2C carbides by proton irradiation inhibits molten salt corrosion in Ni-based alloy

The effect of displacement damage on the corrosion behavior in a molten FLiBe salt environment was investigated. The element distribution and microstructure around the grain boundaries (GBs) after corrosion were characterized. The results show a decrease in corrosion thickness with increasing irradiation dose and the presence of intergranular corrosion. Nanoscales M2C carbides were observed to be distributed, with a denser and thicker distribution in samples with higher irradiation doses. Their distribution depth is related to the Cr depletion region, inhibiting Cr diffusion toward the GBs and surface. Furthermore, the nucleation mechanism of M2C carbides along the GBs and in irradiated regions was revealed, attributed to the combined effects of thermal influences, element preferential dissolution due to corrosion, and irradiation-induced segregation.

Numerical simulation of thermal-flow-magnetic coupling dynamics during P-type monocrystalline silicon removal in electrical discharge machining

To investigate the mechanisms underlying material removal and crater formation on semiconductor silicon in electrical discharge machining (EDM), this study presents a comprehensive thermal-flow-magnetic coupling simulation model, taking into account the synergistic effects of temperature, fluid dynamics and electromagnetic fields. Utilizing the model, the removal dynamics of P-type monocrystalline silicon within a monopulse discharge interval were meticulously simulated. Subsequently, the crater formation mechanism, as well as variations in the temperature and velocity fields, were thoroughly examined. The simulation model’s validity is experimentally confirmed. Findings indicate that an augmentation in pulse duration and thermal energy input precipitates a progressive expansion of the heat-affected zone in silicon. Concurrently, the temperature field’s expanse and the melting-vaporization frontier extend accordingly. The material undergoes instantaneous vaporization upon exposure to the high-temperature heat source. The volumetric expansion of the vapor is substantial, engendering a thermal explosive force that has a significant impact on the molten material. Ejection of material is attributed to the interplay between thermal explosive forces and electromagnetic influences. Experimental observations show that the morphology and dimensions of the simulated crater closely match those of the experimental crater, affirming the model’s capability to elucidate the crater formation mechanism in EDM processes.

In Situ Annealing Effect on Thermally Co-Evaporated CsPbI2Br Thin Films Studied via Spectroscopic Ellipsometry.

All-inorganic cesium lead halide perovskites possess excellent thermal stability, a feature that renders them highly favorable for optoelectronic applications with an elevated thermal budget. Employing a coevaporation approach for their deposition holds promise for manufacturing at an industrial level, owing to improvements in device scalability and reproducibility. For unlocking the full potential of vacuum-evaporated perovskite thin films, it is crucial to delve deeper into their crystallization process, which, as a solid-state reaction, has been less investigated compared to the crystallization process of, most commonly used, solution-based methods. In this work, we employ spectroscopic ellipsometry, a nondestructive, high speed, and high accuracy characterization method, to study the real time annealing effect on thermally coevaporated CsPbI2Br thin films in a temperature range between 25 and 300 °C. We achieve this by developing a singular dynamic model that can be fitted in real time as a function of temperature, providing insights into how thermal annealing influences the perovskite film's morphology and optical constants. Based on the latter, we derive the temperature dependence of the thermo-optic coefficient and Urbach energy as well as analyze the interband transition energies via critical point analysis. We demonstrate that the γ- to β-phase transition can be identified through a pronounced shift in the bandgap energy, whereas the β- to α-phase transition can be discerned by a sharp increase in the film's roughness. We corroborate the obtained fit results with additional in- and ex situ measurements, such as in situ grazing incidence wide-angle X-ray scattering, atomic force microscopy, reflectance/transmittance, and profilometry.

Effects of Wood Drying Temperatures on the Reduction in Mechanical Properties of Japanese Cedar (Cryptomeria japonica D. Don) Perpendicular to Grain

Wood drying is often accompanied by changes in mechanical properties due to external thermal energy. This study examined the influences of drying temperature on the mechanical properties of Japanese cedar based on the partial compression properties and bending properties. Two types of longitudinal specimens with quarter grain on both lateral surfaces were prepared under green conditions, followed by subsequent drying under each drying temperature (20 °C, 40 °C, 60 °C, 80 °C, and 100 °C). Then, the partial compression and bending tests were performed using the respective specimens. Young’s modulus perpendicular to grain, yield stress, and compressive strength obtained by the partial compressive test were highest for wood dried at 20 °C. It was considered that the decrease in mechanical properties was attributed to the thermal influences during drying at 100 °C and other factors such as compressive residual stress and cell walls collapsing at lower temperatures. The strain energy suggested that the effects of drying temperature became apparent, especially in the plastic region during loading in the direction perpendicular to the wood fiber. Bending properties showed little influence on drying temperatures compared to the partial compressive properties, whereas the fractures found under the loading point of the wood dried at 100 °C suggested a reduction in resistance to shear forces.

Investigation of the structural and phase state of detonation multilayer coatings based on NiCr/NiCr–Al2O3/Al2O3 during high-temperature oxidation

This paper presents a study of the structural and phase state of detonation multilayer coatings under hightemperature oxidation. The experiment aimed to find out the effect of high temperatures on the structuralphase state of coatings and their effectiveness in preventing oxidative processes. As a result of the research, it was found that after high-temperature tests, protective phases such as NiCr2O4, Al2O3, and Cr2O3 are formed in the structure of multilayer coatings. These phases were identified to play a key role in preventing intensive oxidation of the metal surface. It was determined that NiCr2O4 provides stability to the metal layer, and Al2O3 and Cr2O3 are effective barriers protecting the surface from aggressive environmental influences. It is important to note that no signs of fracture or detachment were found in the multilayer coatings during the entire experiment. After the first cycle, the uncoated sample experienced peeling of its oxide film, resulting in a significant loss of mass. It was determined that the uncoated steel experiences significantly higher mass loss, indicating a faster formation of oxides on its surface. The experimental data confirm the effectiveness of coatings in protecting against oxidative processes at high temperatures, thereby maintaining the stability and durability of the material under extreme thermal influences.

Managed aquifer recharge in island aquifer under thermal influences on the fresh-saline water interface

Storing and utilizing freshwater in coastal aquifers with managed aquifer recharge (MAR) presents significant challenges, particularly in small island settings where seawater intrusion is a major source of groundwater salinization. Existing studies usually evaluate density-dependent flow under isothermal condition, which neglects the potential impact of temperature on fluid density. To fill the knowledge gap, we performed both laboratory experiments and numerical modeling to investigate the impact of warmer water injection on freshwater storage and extracted water quality for island aquifer. It is found that warmer water (70 °C) injection compromise the “barrier effect” achieved by normal water injection, resulting in a reduced ability to prevent coastal seawater intrusion by, creating an upward hydraulic gradient beneath the injection well. In addition, warm water injection result in a 5 % decrease in freshwater storage capacity for island aquifer. However, by employing a combination of receding tide cycles and intermittent injection-extraction operations, the duration of lowered saline concentration within the extracted water can be extended by approximately 10 % with an 11 % reduction in the overall extracted saline concentration. This study provides valuable insights into the influence of warmer water injection on coastal aquifer quality. The findings from both the laboratory experiments and numerical simulations enhance the understanding of thermal density-dependent dynamics of coastal aquifers, offering valuable guidance for effective freshwater storage and usage in island settings.

Influence of multisource errors of oil film contact surface on motion accuracy of hydrostatic guideway

PurposeThis study aims to explore the impact of multisource deformation errors on the oil film contact surface, which arise from manufacturing, assembly, oil pressure and thermal influences, on the motion accuracy of hydrostatic guideway.Design/methodology/approachUsing thermal-structural coupling simulations, this research investigates the effects of assembly, oil pressure and thermal factors on deformation errors of the oil film contact surface. By integrating these with manufacturing errors, a profile error model for the oil film contact surface is developed, characterizing the cumulative effect of these errors. Using kinematic theory and progressive Mengen flow controller characteristics, the motion error at any position of the hydrostatic guideway is quantified, examining how surface error traits impact motion accuracy.FindingsThe error averaging effect is affected by the profile error of oil film contact surface. Meanwhile, the motion accuracy of hydrostatic guideway is highly sensitive to the oil film contact surface error amplitude.Originality/valueThis approach allows for precise prediction and analysis of motion accuracy in hydrostatic guideways during the design and manufacturing stages. It also provides guidance for planning process tolerances.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0063/

Formation mechanism and evolution of interfacial residual stress between composite propellant and rubber liner during curing process

This study focuses on the solid rocket engines, which are commonly used in satellite launches and space exploration. The residual stress at the interface between the composite propellant and rubber liner generated during the curing process can lead to several issues, such as debonding, shrinkage, and deformation. This study aims to examine the mechanism and evolution law of the residual stress development. A finite element model is established to examine the residual stress during the full curing process. The composite propellant undergoes intricate temperature and curing gradients. The stress in various parts of the propellant and liner is monitored throughout the entire curing cycle. The propellant's temperature exhibits a delayed response during the heating and cooling phases of the curing process. The interface undergoes curing throughout the stage of constant temperature, with its chemical shrinkage primarily taking place prior to the cooling step. Considerable stress exists at the contact before cooling. The stress caused by thermal influences becomes more noticeable during the cooling phase. The influence of propellant composition and curing process parameters on interface stress is investigated. In addition, a specific vision-based device is innovatively designed to monitor deformation changes during the curing process. The key parameters of the simulation are optimized by combining the detected deformation, aiming to minimize the deformation difference between the experiment and the simulation, so as to realize the corresponding stress evaluation. The measurement results show an average deformation error of 10.71% and an average stress error of 10.58%.

Impact of heat infiltration on the cooling capacity evaluation of an evaporator for household refrigerator-freezers with a non-adiabatic capillary tube

This study experimentally evaluates the cooling capacity of an evaporator in household refrigerator-freezers, typically scaled in hundreds of Watts, and investigates the impact of heat infiltration from the environment. Despite the scarcity of both quantitative and qualitative research in this area, this study provides data from a lab-scaled vapor compression refrigeration system that mimics a real-world side-by-side refrigerator-freezer. Experiments were conducted under conditions reflecting the household refrigerator-freezer, yielding 74 data points under quasi-steady state conditions. Despite careful insulation, heat infiltration from the ambient to the refrigerant flow in the evaporator occurred due to the significant temperature differential, impacting the cooling capacity evaluation fatally with a heat balance error of 26%. However, when considering the effects of heat infiltration, the error in the evaporator heat balance dropped to 6% significantly. The findings highlight the sensitivity of evaporator’s cooling capacity, less than 300 W, to external thermal factors during empirical evaluation. This study underscores the challenges of heat infiltration and the importance of considering such factors when assessing evaporator cooling capacity. The provided comprehensive analyses significantly contribute to the experimental prototyping of evaporators, emphasizing the need to account for external thermal influences during the evaluation process.

Flexural vibration suppression behavior of sleeved phononic crystal pipes in thermal environment

Design idea of phononic crystal has been introduced into vibration suppression of pipes and presents expected effects. During service period, thermal environment is a common factor that may change the dynamic behavior of system. In this work, thermal influences on wave attenuation effect are studied for the single-component PC pipe which is constructed by attaching sleeves to the original bare pipe. Under the preloading effect of thermal stresses, flexural wave bandgap shifts toward the lower frequency range with temperature increment. Bandwidth gets wider for pipes with sleeves of a relative length larger than 0.5, while the bandgap narrows down or even closes up for pipes with shorter sleeves. The opposite variation trends are caused by the reversal of edge modes and the unequal responses of the two edge frequencies to thermal stress stiffness. Deeper reason is the discrepancy in determining factor for frequency between the two edge modes. As a result, the two edge frequency loci drop asynchronously under thermal load, and the transition point of bandgap shifts leftward. A thermo-vibrational joint test system is constructed and flexural wave transmittance is measured, for the first time, for a heated PC pipe. Experimental phenomena and simulation results suggest that the initial deflection and non-ideal constraint of the specimen make the attenuation band present opposite variation trends compared to the ideal model. The former strengthens the stiffness of the PC pipe, and the latter weakens the thermal influence on the PC pipe. Both the two non-ideal factors have a more significant impact on starting frequency of the attenuation band due to the difference in sensitivity of bandgap edge frequencies to stiffness perturbation of the PC pipe.

Approach to Determine the Limiting Shear Stress of Lubricants at High Pressures Based on Traction Mapping

Typical lubricants behave in a non-Newtonian manner under conditions of high shear and high pressure, as is commonly observed in lubricated rolling/sliding contacts. To optimize and predict the friction therein, knowledge of the high-pressure rheological behaviors of lubricants and limiting shear stress (LSS) is essential. This study developed an approach for determining the LSS of lubricants based on friction mapping of rolling/sliding contacts, using a ball-on-disc traction machine. The main contribution lies in the introduction of a practical approach for the selection of a proper entrainment velocity for determining the LSS, with reduced thermal influences and near isothermal conditions. The proposed approach enables full film lubrication, while keeping the film as thin as possible to prevent excessive shear heating and, thus, thermal effects. The LSS of two lubricants, PAO40 and complex ester, has been measured at pressures ranging from 1.2 GPa to 1.7 GPa. A bilinear model has been used to describe the variation of LSS with pressure. The impact of entrainment velocity selection on the measurement of LSS is also discussed.

Thermal and viscoelastic coupled influences analysis on mixed lubrication in dynamic journal bearings

The interaction of temperature variations and viscoelastic deformation is critical in dynamically loaded journal bearings, especially under fluctuating heavy load conditions. Previous studies have not fully explored the coupling of these two factors. Addressing this gap, this research introduces a novel transient mixed lubrication model that simultaneously considers thermal and viscoelastic effects. This model reveals intricate dynamics influencing the lubrication performance of journal bearings. The findings show that the combined impact of thermal and viscoelastic factors significantly alters the amplitude and phase of lubrication performance parameters. Notably, thermal effects tend to decrease oil film pressure while increasing asperity contact pressure, whereas viscoelastic effects enhance the oil film pressure peak and adjust its phase, concurrently reducing asperity contact pressure. Moreover, varying the eccentric speed profoundly influences the interplay between bearing thermal and viscoelastic effects. This study contributes to a deeper understanding of mixed lubrication in journal bearings and provides technical support for more accurate and predictive reliability improvement in complex mechanical systems.

Influence of Pressure, Temperature and Discharge Rate on the Electrical Performances of a Commercial Pouch Li-Ion Battery

In this study, the performances of a pouch Li-ion battery (LIB) with respect to temperature, pressure and discharge-rate variation are measured. A sensitivity study has been conducted with three temperatures (5 °C, 25 °C, 45 °C), four pressures (0.2 MPa, 0.5 MPa, 0.8 MPa, 1.2 MPa) and three electrical discharge rates (0.5 C, 1.5 C, 3.0 C). Electrochemical processes and overall efficiency are significantly affected by temperature and pressure, influencing capacity and charge–discharge rates. In previous studies, temperature and pressure were not controlled simultaneously due to technological limitations. A novel test bench was developed to investigate these influences by controlling the surface temperature and mechanical pressure on a pouch LIB during electrical charging and discharging. This test rig permits an accurate assessment of mechanical, thermal and electrical parameters, while decoupling thermal and mechanical influences during electrical operation. The results of the study confirm what has been found in the literature: an increase in pressure leads to a decrease in performance, while an increase in temperature leads to an increase in performance. However, the extent to which the pressure impacts performance is determined by the temperature and the applied electrical discharge rate. At 5 °C and 0.5 C, an increase in pressure from 0.2 MPa to 1.2 MPa results in a 5.84% decrease in discharged capacity. At 45 °C the discharge capacity decreases by 2.17%. Regarding the impact of the temperature, at discharge rate of 0.5 C, with an applied pressure of 0.2 MPa, an increase in temperature from 25 °C to 45 °C results in an increase of 4.27% in discharged capacity. The impact on performance varies significantly at different C-rates. Under the same pressure (0.2 MPa) and temperature variation (from 25 °C to 45 °C), increasing the electrical discharge rate to 1.5 C results in a 43.04% increase in discharged capacity. The interplay between temperature, pressure and C-rate has a significant, non-linear impact on performance. This suggests that the characterisation of an LIB would require the active control of both temperature and pressure during electrical operation.

A precise method for the spectral adjustment of LED and multi‐light source solar simulators

AbstractSolar simulators based on light‐emitting diodes (LEDs) usually consist of many spectrally different LEDs, which in sum produce a sun‐like spectrum. On the one hand, this results in the advantage of a high spectral tunability of these systems and on the other hand, however, also in the challenge of a high number of parameters which have to be set for the adjustment of a suitable simulator spectrum. Multijunction solar cells consisting of series‐connected subcells are very sensitive to spectral irradiance conditions, which are affecting the current and the fill factor of the device. A precise adjustment of the simulator spectrum based on the spectral responsivity of the subcells is therefore essential for accurate multijunction measurements. Therefore, the number of spectrally different light sources used should be at least as high as the number of subcells in the device under test. However, for the measurement of multijunction devices, the much higher number of spectrally different light sources in common LED solar simulators results in a plethora of different simulator spectra, potentially suitable for the measurement. Furthermore, the nonlinear intensity characteristics of the utilized LEDs as well as the distance‐dependent illumination uniformity of such solar simulators add complexity when aiming for a precise spectral adjustment. To tackle these challenges, a new spectral adjustment procedure which is based on a least square's solution algorithm and the definition of appropriate boundary conditions for the calculation of suitable simulator settings is introduced in this publication. Focusing on measurements carried out under constant illumination makes the presented method especially applicable for perovskite‐on‐silicon multijunction devices. Therefore, an adapted method for the determination of the solar simulator's spectral properties, considering thermal influences which are particularly relevant when carrying out continuous illumination measurements, is introduced in this work. The presented method is verified applying it on a Wavelabs SINUS 220 LED solar simulator by performing a measurement comparison on a multijunction solar cell with Fraunhofer ISE CalLab's well‐established multilight source solar simulator.

Evaluating the spindle error of the roundness measurement device

Roundness measurement devices use a probe that converts the displacement into an electrical signal. In addition to the out-of-roundness information, the measurement signal can contain undesirable noise due to mechanical, electrical, thermal, and other influences that can lead to an error in the measurement result. Errors in the rotation of the measuring device spindle are often recognised as the most significant cause of deviation of roundness signal. A prevalent technique for evaluating the precision of spindle rotation entails calibration with the precise measuring sphere. The measurement results incorporate not just the form of the rotation error in the spindle but also other sources of error that can be characterized as random noise. A novel approach for eliminating random noise bias, based on the reduction of Fourier terms proposed by Haitjema and Morel, was implemented to enhance the determination of spindle error.

Improving the Energy Efficiency of Machine Tools using a Thermal Storage Unit based on a Phase Change Material

Today there are many ideas investigated to find ways for industries to become more environmentally friendly and sustainable. To reduce the energy consumption of machine tools and thus increase the efficiency of production, this paper discusses the idea of a heat accumulator based on a phase change material (PCM). In the context of biologisation in production technology, this work is based on the principle of heat storage in equi-warm organisms.Since machine tools deform under thermal influences and thus affect the machining process, they are often operated in idle mode before the work process to reach a thermally stable state and reduce thermally induced deformation during the production process. The machine is actively tempered using the cooling circuit to keep the temperature plateau constant.The idea of the PCM unit presented in this paper is to store this excess and otherwise dissipated energy. This can be used before the machines next process cycle to induce heat into the machine and reach the stable temperature plateau without operating the machine. The conditions under which the energy consumption can be reduced using this method and thus making the operation more sustainable are discussed and first simulations show that the goal is achievable.

Recent advances in tunable solid-state emission based on α-cyanodiarylethenes: from molecular packing regulation to functional development.

The design and development of organic solid-state luminescent materials stand as crucial pillars within the realm of contemporary photofunctional materials. Overcoming challenges such as concentration quenching and achieving tailored luminescent properties necessitates a judicious approach to molecular structure design and the strategic utilization of diverse stimuli to modulate molecular packing patterns. Among the myriad candidates, α-cyanodiarylethenes (CAEs) emerge with distinctive solid-state luminescent attributes, capable of forming self-assembled packing structures with varying degrees of π-π stacking. This characteristic endows them with potential in the field of intelligent molecular responsive materials and optoelectronic devices. This tutorial review embarks on an exploration of design strategies geared towards attaining tunable solid-state emission through customized packing of CAEs. It explores the utilization of stimuli responses, including such as mechanical forces, light irradiation, solvent interactions, thermal influences, as well as the utilization of co-assembly methodologies. The overarching aim of this review is to provide a widely applicable platform fostering the flourishing development of modern organic photofunctional materials through integrating principles of molecular engineering, organic optoelectronics, and materials science.

Laser color marking of stainless steel – Investigation of the fluence-dependent and thermal mechanisms in generating laser induced surface modifications

Laser color marking is an attractive process to generate functional, aesthetic and durable colorations on various suitable metals such as stainless steel or titanium. The color generation is mainly based on interference effects on thin oxide layers, usually induced by nanosecond pulsed laser irradiation. Due to the large number of mutually influencing processing parameters and different thermal, chemical, structural and topological influences on the coloring results, the process is still not fully understood. Moreover, the reproducibility of the markings and the processing times often do not meet the requirements of industrial manufacturing processes. To improve the understanding of the underlying phenomena comparable colors are generated using different parameter sets. Spectroscopic, microscopic and SEM/EDS analyzes are carried out to investigate the effects of the surface topology, oxide layer properties, chemical composition and heat accumulation on the marking results.