Effect Of Heating Research Articles

High temperature perturbs physicochemical parameters and fatty acids composition of safflower (Carthamus tinctorius L.).

Future climates will realise increasingly frequent extreme weather events, which will impact on the quantum and quality of crop production. While effects of extreme heat on crop production have been well studied hitherto, there remains a dearth of knowledge pertaining to the impacts of extreme heat on grain quality. As such, our purpose here was to evaluate the effects of terminal heat stress on the physicochemical properties and composition of seed oil of safflower plants. Using two contemporary cultivars with varying genetic tolerance to heat stress (Faraman and Sofeh), we found that exposure to extreme heat reduced grain yield by 53-57%. Four fatty acids (palmitic, stearic, oleic and linoleic acid) comprised 96-99% of total fatty acid methyl esters; relative composition varied in response to heat stress and other environmental conditions. In the first experimental year (2017-18), saturated fatty acids in Sofeh and Faraman cultivars increased by 69% and 18% respectively, while unsaturated fatty acids decreased by 9% and 4%, respectively. In the second experimental year (2018-19), saturated fatty acids increased by 10% in Sofeh and by less than 1% in Farman, while unsaturated fatty acids in both cultivars were not significantly altered. Physicochemical parameters differed across years and cultivars; exposure to high temperature increased chlorophyll and carotenoid content in Sofeh, but decreased the said parameters in Faraman. In 2017-18, effects of heat stress on thiobarbituric acid were variable, but in 2018-19, thiobarbituric acid increased in both cultivars. In all cases, saponification and iodine content increased in response to heat stress. In sum, the fatty acid profile of safflower exposed to terminal heat stress was less affected compared with oil physicochemical parameters, due to greater temperature sensitivity of the latter.

Towards p-11B medium configurations with high Pfus/PBrems ratios

Aneutronic p-11B nuclear fusion is promising for clean energy production, as it produces three (3) alpha particles with 8.7 MeV total energy. However, the main difficulty for p-11B fusion ignition (Q = Pfus/PBrems≥ 1) concerns the nuclear cross section and thus, reactivity efficiency at higher than 200 keV medium temperatures. To overcome this difficulty, the present work emphasizes on the numerical investigation of medium schemes (configurations) with enhanced reactivity. The configurations refer to the addition of energetic protons in a low-density 11boron or proton–11boron medium (n = 1020 m−3), with (np/nB) > 1 for Bremsstrahlung losses optimization and initial temperature in the range of 1 keV ≤ Tin≤ 400 keV. A self-consistent multi-fluid global particle and energy balance code, including collisions between all medium species (p, 11B, e, α), is used for the description of the temporal evolution of all fusion medium physical parameters and the evaluation of the optimum initial conditions for the obtainment of Q ≥ 1. The numerical simulation results show that the coupling between the 200 keV < Ep,0≤ 750 keV energetic protons and the 1 keV ≤ Tin≤ 400 keV initial fusion medium leads to ignition, 1 ≤ Q < 1.4, below Tin= 100 keV. In all the presented initial medium temperature cases, and especially, the lower (<) than 100 keV, the ignition condition (Pfus/PBrems) > 1 arises, as a consequence of the chain reactions and the related avalanche alpha heating effect.

Anisotropic Heat Transfer in a Fibrous Membrane with Hierarchically Assembled 2D Materials.

Effective heat redistribution in specific directions is vital for advanced thermal management, significantly enhancing device performance by optimizing spatial heat configurations. We have designed and fabricated a hierarchical fibrous membrane that enables precise heat directing. By integrating hierarchical structure design with the anisotropic thermal conductivity of two-dimensional (2D) materials, we developed a fibrous membrane for anisotropic heat transfer. Such a structure is fabricated by aligning a 1D structured fiber in the 2D plane to achieve anisotropy at each scale level. The fiber units, where 2D nanosheets circumferentially and axially aligned, achieved a high axial thermal conductivity of 16.8 W·m-1·K-1 and advanced heat directing ability, confirmed by characterizations and simulations. The assembled membrane demonstrated an exceptional tensile strength (365 MPa) and high thermal conductivity (10.5 W·m-1·K-1) along the fiber axis. Our membranes are seen as a refined model for thermal management materials, combining the benefits of heat spreaders and thermal interface materials, thus being proficient in directing heat along programmed pathways. A practical wireless charging cooling demonstration illustrated this. Our methodology also proved versatile with different 2D fillers and various geometries. This research presents a method to achieve precise heat directing at the material's level, facilitating the systematic design of thermal management in electronics.

Effect of Rapid Heating and Quenching on Microstructure and Mechanical Properties of High Strength Low Alloy Steel

Effect of Rapid Heating and Quenching on Microstructure and Mechanical Properties of High Strength Low Alloy Steel

Biogas Production from a Solar-Heated Temperature-Controlled Biogas Digester

This research paper explores biogas production in an underground temperature-controlled fixed dome digester and compares it with a similar uncontrolled digester. Two underground fixed-dome digesters, one fitted with a solar heating system and a stirrer and the other one with an identical stirrer only, were batch-fed with cow dung slurry collected from the University of Fort Hare farm and mixed with water in a ratio of 1:1. The solar heating system consisted of a solar geyser, pex-al-pex tubing, an electric ball valve, a water circulation pump, an Arduino aided temperature control system, and a heat exchanger located at the centre of the digester. Both the digesters were intermittently stirred for 10 min every 4 h. The digester without a heating system was used as a control. Biogas production in the two digesters was compared to assess the effect of solar heating on biogas production. The total solids, volatile solids, and the chemical oxygen demand of the cow dung used as substrate were determined before and after digestion. These were compared together with the cumulative biogas produced and the methane content for the controlled and uncontrolled digesters. It was observed that the temperature control system kept the slurry temperature in the controlled digester within the required range for 82.76% of the retention period, showing an efficiency of 82.76%. Some maximum temperature gradients of 7.0 °C were observed in both the controlled and uncontrolled digesters, showing that the stirrer speed of 30 rpm was not fast enough to create the needed vortex for a uniform mix in the slurry. It was further observed that the heat from the solar geyser and the ground insulation were sufficient to keep the digester temperature within the required temperature range without any additional heat source even at night. Biogas yield was observed to depend on the pH with a strong coefficient of determination of 0.788 and 0.755 for the controlled and uncontrolled digesters, respectively. The cumulative biogas was 26.77 m3 and 18.05 m3 for controlled and uncontrolled digesters, respectively, which was an increase of 33%. The methane content increased by 14% while carbon dioxide decreased by 10% from the uncontrolled to the controlled scenario. The percentage removal of the TS, VS, and COD was 66.26%, 76.81%, and 74.69%, respectively, compared to 47.01%, 60.37%, and 57.86% for the uncontrolled situation. Thus, the percentage removal of TS, VS, and COD increased by 19.25%, 16.44%, and 16.89%, respectively.

Current–Voltage–Friction Characteristics of Grease in Electromechanically Loaded Sliding Contacts

Abstract Electromechanically loaded contacts, which have relative motion between the contacting parts, experience severe damage compared to mechanically loaded contacts. The electromechanical environment occurs when different types of current flow through the bearings of traction motors due to the usage of electronic speed control devices. The current passage through the contact depends on the voltage potential developed across the contact. Grease is commonly used as a lubricant, and degradation and evaporation of lubricant due to the joule heating effect are concerns in electromechanical contacts. This study reports the current–voltage–friction characteristics of lithium mineral oil grease using a ball-on-disk configuration under combined electrical and mechanical loading. The characteristics indicated a transition of the lubricated contact from a non-conducting state to a conducting state with increased applied voltage. Two critical voltages are identified: one where the friction is observed to rise and the other where the current flow rapidly increases, leading to accelerated damage to the lubricant by inducing a significantly high temperature. The study helps in identifying permissible voltage levels for operating bearings safely from the perspective of grease lubricant using simplified ball-on-disk experiments.

Nuclear burning in an accretion flow around a stellar-mass black hole embedded within an AGN disk

Abstract A stellar-mass black hole, embedded within the accretion disk of an active galactic nuclei (AGN), has the potential to accrete gas at a rate that can reach approximately ∼109 times the Eddington limit. This study explores the potential for nuclear burning in the rapidly accreting flow towards this black hole and studies how nucleosynthesis affects metal production. Using numerical methods, we have obtained the disk structure while considering nuclear burning and assessed the stability of the disk. In contrast to gas accretion onto the surface of a neutron star or white dwarf, the disk remains stable against the thermal and secular instabilities because advection cooling offsets the nuclear heating effects. The absence of a solid surface for a black hole prevents excessive mass accumulation in the inner disk region. Notably, nuclear fusion predominantly takes place in the inner disk region, resulting in substantial burning of $\rm ^{12}C$ and $\rm ^{3}He$, particularly for black holes around M = 10 M⊙ with accretion rates exceeding approximately ∼107 times the Eddington rate. The ejection of carbon-depleted gas through outflows can lead to an increase in the mass ratio of oxygen or nitrogen to carbon, which may be reflected in observed line ratios such as $\rm N\, V/C\, IV$ and $\rm O\, IV/C\, IV$. Consequently, these elevated spectral line ratios could be interpreted as indications of super-solar metallicity in the broad line region.

Abstract 4137820: Extreme heat and cardiovascular disease in a changing climate: An urgent need for risk management and health research

Background: Extreme heat can trigger or exacerbate cardiovascular disease (CVD) through ischemia or thrombosis, and its deleterious impacts are inclined to worsen as increased heat exposure and heightened vulnerability from climate change interacted with natural and social environment. Research Questions: Previous studies have primarily focused on quantifying the increased risk of CVD due to heat exposure, while lacking a comprehensive understanding of the association, underlying mechanisms, and vulnerability in CVD patients. Consequently, there is a scarcity of clinical and public health interventions aimed at preventing the convergence of extreme heat exposure and the risk of CVD within the context of climate change. Methods: We conducted a systematic search in PubMed, Embase, and Web of Science from inception to December, 2023, and we retrieved articles which assessed the effects of extreme heat or climate change on CVD. Results: In this review, we outline the existing evidence on the epidemiology and pathophysiological mechanisms that elucidate how extreme heat affects the risk of CVD. Extreme heat is associated with increased risks for CVD morbidity and mortality, where older persons, low socioeconomic status, pre-existing medical conditions, and unfavorable living environments confer greater susceptibility to heat. The adverse effects of extreme heat on cardiovascular system involved a wide range of complex mechanisms between different organs and regulatory pathways (Figure 1). Additionally, we identify the factors that contribute to the vulnerability of CVD patients to heat exposure. The discrepancy in heat-related risk can be attributed to individual susceptibility, sociocultural factors, population temperature adaptations, and environmental factors. Future climate change is projected to exacerbate the burden of extreme heat, particularly due to the interaction of air pollution, population aging, and urbanization (Figure 2). Conclusions: Addressing extreme heat should be within the framework of the prevention of CVD. Health professionals and scientists are responsible for mitigating the cardiovascular effects mediated by extreme heat, with an emphasis on engaging in risk management tactics and health research to implement preventive strategies. As CVD is a climate sensitive disease, evidence-based interventions during heat extremes are urgently needed to cope with the cardiovascular risks associated with the inevitable trajectory of climate change.

Thermal and flow dynamics of an inclined air heat exchanger equipped with spring turbulators in the transition flow regime

AbstractThe research involves an experimental investigation into the performance of a flow assisting air heat exchanger under varying angular orientation and uniform external heat fluxes without and with spring turbulators. The investigation was performed for Reynolds numbers ranging from 511 to 9676 and inclination angle 15° and 30°. Three heat fluxes (2, 3, and 4 kW/m2) were applied to the test section to investigate the effect of external surface heating on the range of transition flow regime and thermohydraulic performance. Transition from laminar to turbulent flow for plain channel at different heat fluxes and inclinations occurs within specific Reynolds number ranges: 2436–4446 for 15° inclination at 4 kW/m2, 2574–4289 at 3 kW/m2, and 2850–4152 at 2 kW/m2; for 30° inclination, the ranges are 2518–4151, 2712–4361, and 2992–4346 at the respective heat fluxes. When it comes to the effect of inclination on Nusselt number, the transition occurs sooner at lower angles, but is delayed as the angle increases. Additionally, the Nusselt number decreases as the angle of inclination increases. When comparing the Nusselt numbers of plain tubes to those with spring turbulators, the latter shows a significantly greater enhancement. In laminar flow, a maximum 100% deviation exists between highest and lowest friction factors, decreasing to 75% with increasing Reynolds number; all insert configurations exhibit highest friction factor at 15° due to stronger buoyancy forces.

Effect of Perilla Seeds Pretreatment on the Volatile Profile and Flavor Characteristics of Perilla Oil: Comparison of Oven, Infrared, and Microwave Heating

ABSTRACTThe effects of microwave (MW), infrared (IF), and oven heating (OH) on the volatile profile and flavor of perilla oil were investigated in this study. Physicochemical properties and Maillard reaction products of perilla oil were measured to investigate the potential pathway of flavor formation. Sensory evaluation, combined with headspace‐solid‐phase microextraction‐gas chromatography‐mass spectrometry (HS‐SPME‐GC‐MS) and electronic nose (E‐nose) techniques, was employed to determine the categories and contents of volatile compounds in perilla oil. Three heating treatments all effectively increased the content of odor‐active volatile compounds in perilla oil. Samples treated by MW contained higher concentration of heterocyclics, while samples treated using IF and OH contained more aldehydes. The content of (E,E)‐2,4‐heptadienal were highly correlated to P‐AV. The contents of pyrazines and furans were positively correlated with A420nm, particularly 2,5‐dimethyl‐pyrazine, trimethyl‐pyrazine, and 2‐pentylfuran. The content of hexanal and (E)‐2‐hexenal showed a negative correlation with the content of heterocyclic compounds. Consequently, the volatile compounds in perilla oils were generated through three potential mechanisms: lipid oxidation, the Maillard reaction, and their synergistic effect.

Enhanced Electrocaloric Effect of PVDF-based Polymer Composite with Surface Modified AlN.

Poly(vinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) relaxor ferroelectric polymer exhibits a modest electrocaloric effect (ECE) at a low electric field near room temperature and a low thermal conductivity. The low thermal conductivity causes poor heat transfer when the terpolymer is used as a cooling device, even when the ECE of the polymer is substantial. By incorporating aluminum nitride (AlN) nanoparticles, which possess high thermal conductivity and good electrical insulation properties, into polymer matrices, we can enhance both the thermal conductivity and the ECE. However, weak bonding at the AlN-polymer interface can lead to a reduced breakdown electric field. Therefore, surface modification of AlN nanoparticles is performed to strengthen the chemical bonding between AlN and the terpolymer, thereby increasing the breakdown electric field. Following the addition of surface-modified nanoparticles, the breakdown electric field of the composite films remained around 240 MV/m, which is comparable to that of the pristine polymer film. Furthermore, the ECE and thermal conductivity were improved by 44% and 55%, respectively. We found three factors influencing the ECE, including the interface effect, the change in ferroelectric-paraelectric phase transition behavior, and the Joule heating effect. To assess the interfacial effect on the ECE, composite films with AlN particles of four different sizes were prepared. It was found that as the size of the nanoparticles increased, which resulted in a decreased interface area, the ECE decreased correspondingly. This finding further confirms the significant impact of the interface area in the composites on the ECE.

Managing Residual Heat Effects in Femtosecond Laser Material Processing by Pulse-on-Demand Operation

Femtosecond laser processing combines highly accurate structuring with low residual heating of materials, low thermal damage, and nonlinear absorption processes, making it suitable for the machining of transparent brittle materials. However, with high average powers and laser pulse repetition rates, residual heating becomes relevant. Here, we present a study of the femtosecond laser pulse-on-demand operation regime, combined with regular scanners, aiming to improve throughput and quality of processing regardless of the scanner’s capabilities. We developed two methods to define the needed pulse-on-demand trigger sequences that compensate for the initial accelerating scanner movements. The effects of pulse-on-demand operation were studied in detail using direct process monitoring with a fast thermal camera and indirect process monitoring with optical and topographical surface imaging of final structures, both showing clear advantages of pulse-on-demand operation in precision, thermal effects, and structure shape control. The ability to compensate for irregular scanner movement is the basis for simplified, cheaper, and faster femtosecond laser processing of brittle and heat-susceptible materials.

Suppression of plasmonic heating effect in SERS measurement by coating graphene on the Ag@AAO substrate surface

Suppression of plasmonic heating effect in SERS measurement by coating graphene on the Ag@AAO substrate surface

Surface integrity and mechanical properties of small elements fabricated through LPBF and post-processed with heat treatment and abrasive machining

AbstractThe present research analyzes the impact of heat treatment atmosphere followed by finishing surface machining of small elements of Inconel 939 fabricated through laser powder bed fusion (LPBF). The analysis involved annealing in two gas mediums, solution treatment, and aging to achieve the desired microstructure and mechanical properties. The finishing surface was performed using various variants of abrasive machining. A more than fivefold reduction in the average roughness height Ra from 5.6 µm to 1.15 µm was achieved using metal balls as an abrasive, which was required for further processing. Residual stress tests have shown that due to heat and abrasive treatment, tensile stresses change into compressive ones. After printing, samples are characterized by tensile residual stresses on the surface (+ 428 MPa), while after heat treatment, compressive stresses occur (− 179 MPa). Abrasive machining with metal balls increases the value of compressive stresses to − 464 MPa. In addition, the impact of post-processing on the microstructure of Inconel 939 was discussed in terms of mechanical properties. The yield strength of 1184 MPa and elongation values of 19.3% were obtained for samples after HT in an argon atmosphere and abrasive machining with a ceramics roller. These studies provide valuable new information on the effective heat treatment and optimization of the finishing machining of Inconel 939, especially in achieving the desired surface roughness, microstructure, and mechanical properties for aerospace applications.

MHD Casson Fluid Flow over a Stretching Surface with Suction, Double Stratification, and Heat and Mass Transfer Effects

Abstract In this article, we investigated the flow of a magnetohydrodynamic Casson fluid across an extending surface with exponential permeability in a double-stratified medium. Thermal radiation, suction, heat sources, viscous dissipation, and chemical reactions drive the stream field. We converted the flow describing partial differential equations into terms of ordinary differential equations by applying appropriate transformations. Next, we utilised the bvp4c package in Matlab to obtain numerical solutions for these equations. We explored and graphically showed the implications of different non-dimensional governing parameters for temperature, concentration, and velocity profiles. After analysis, we provide a tabular presentation of the friction factor, Nusselt, and Sherwood numbers. The Casson fluid temperature shows a rising trend for the solutal stratification parameter and a decreasing trend for the thermal stratification parameter, while the Casson fluid velocity shows a declining trend towards both of these parameters. The Casson fluid concentration also behaves differently depending on the stratification parameter; for example, it increases for thermal stratification and decreases for solutal stratification. We notice that an increase in the Casson parameter's value suppresses the velocity field. However, as the Casson parameter increases, both the temperature and the concentration improve. Furthermore, comparisons with previously published findings also support the current results. \sethlcolor{yellow}\hl{The study of MHD Casson fluid flow that includes suction, dual stratification, and the effects of heat and mass transfer is very useful in many areas, such as polymer processing, metallurgical engineering, biomedical applications, environmental sciences, and advanced cooling technologies.

Prediction of performance and turbulence in ITER burning plasmas via nonlinear gyrokinetic profile prediction

Abstract Burning plasma performance, transport, and the effect of hydrogen isotope (H, D, D-T fuel mix) on confinement has been predicted for ITER baseline scenario (IBS) conditions using nonlinear gyrokinetic profile predictions. Accelerated by surrogate modeling (Rodriguez-Fernandez et al 2022 Nucl. Fusion 62 076036), high fidelity, nonlinear gyrokinetic simulations performed with the CGYRO code (Candy et al 2016 J. Comput. Phys. 324 73), were used to predict profiles of Ti , Te , and ne while including the effects of alpha heating, auxiliary power (NBI + ECH), collisional energy exchange, and radiation losses inside of r / a = 0.9. Predicted profiles and resulting energy confinement are found to produce fusion power and gain that are approximately consistent with mission goals ( P fusion = 500 MW at Q = 10) for the baseline scenario and exhibit energy confinement that is within 1σ of the H-mode energy confinement scaling. The power of the surrogate modeling technique is demonstrated through the prediction of alternative ITER scenarios with reduced computational cost. These scenarios include conditions with maximized fusion gain and an investigation of potential resonant magnetic perturbation (RMP) effects on performance with a minimal number of gyrokinetic profile iterations required (3–6). These predictions highlight the stiff ITG nature of the core turbulence predicted in the ITER baseline and demonstrate that Q > 17 conditions may be accessible by reducing auxiliary input power while operating in IBS conditions. Prediction of full kinetic profiles allowed for the projection of hydrogen isotope effects around ITER baseline conditions. The gyrokinetic fuel ion species was varied from H, D, and 50/50 D-T and kinetic profiles were predicted. Results indicate that a weak or negligible isotope effect will be observed to arise from core turbulence in IBS conditions. The resulting energy confinement, turbulence, and density peaking, and the implications for ITER operations will be discussed.

Dynamics of Viscous Jeffrey Fluid Flow Through Darcian Medium With Hall Current and Quadratic Buoyancy.

This contribution builds on existing studies by investigating the dynamics of Hall current in Jeffery fluid under radiative heat, convective boundary conditions, Joule heating, and Darcy dissipation. Hall current, an important phenomenon in engineering applications involving strong magnetic fields, highlights the impact of electromagnetic force in examining blood flow rate, determining charge drift velocity, density, and movement, and is used in power generators and high-voltage transformers. This analysis incorporates dissipative and thermal radiative heat and employs the effects of Hall current and Joule heating, resulting from porous medium resistance, to derive the partial differential equationsgoverning the dynamic systems. These equationsare then reduced to ordinary differential equations (ODEs) through similarity variables. The Galerkin weighted residual method (GWRM) is employed to examine the dynamics of Hall current and quadratic thermal buoyancy, shedding light on the thermal properties and hydrodynamics of Jeffrey fluid convection within a porous medium. The analysis reveals that in the presence of an applied magnetic field, the contribution of Hall current to flow and heat dynamics induces a magnetic force that enhances fluid motion and negatively impacts heat energy patterns. The imposition of dissipative heat physically increases the fluid temperature, owing to an increase in buoyancy current. The occurrence of thermal radiation, Hall current, viscous dissipation, and Joule heating can efficiently optimize the rate of heat transfer and shear stress. Moreover, the tabular results indicate that Jeffrey fluid, exhibiting higher relaxation time, will experience a lower friction coefficient and heat transferrate.

The state and future of extreme heat studies in Southeast Asian megacities: risk, impacts and adaptation strategies in a warming world

Abstract Southeast Asian cities are increasingly affected by heat-related phenomena and various climate-related disasters; however, research on urban heat in this region remains limited compared to other areas. This paper employs bibliometric and thematic analyses to investigate studies on extreme heat in mega-urban areas of Southeast Asia, with a particular focus on the risks and impacts faced by vulnerable populations, as well as their adaptation and mitigation strategies. The bibliometric analysis visualises the research landscape, identifying key clusters and highlighting prevalent themes and gaps. It reveals a predominant emphasis on characterising extreme heat and analysing urban temperature variations through satellite and meteorological data, which underscores a significant lack of research on the socio-economic factors affecting at-risk communities. The thematic analysis further examines how existing studies address these socio-economic vulnerabilities and evaluates the adaptation strategies employed, particularly concerning land use changes driven by population growth. Our findings indicate that, while there are studies addressing urban heat in Southeast Asia, their quantity is relatively small compared to the extensive body of research focused on other regions. Strategies to mitigate the effects of extreme heat on mental and social well-being emphasise the importance of green infrastructure and public spaces. There is also a pressing need to enhance urban planning and design to ensure that adaptation measures are inclusive of at-risk, lower-income communities. Understanding the complexities of the risks and impacts of extreme heat on urban populations is crucial for developing effective, context-specific adaptation strategies that prioritise the needs of vulnerable populations and promote equitable, sustainable urban development.

SIMULATION OF PREHEATING AND HEATING WHEN CONNECTING POLYETHYLENE PIPES WITH ELECTROFUSION COUPLINGS

Existing machines for electrofusion welding of polyethylene pipes provide a high-quality connection at air temperatures no lower than minus 10 °C. However, if welding is required at lower temperatures, a layer of heat-insulating material is used to reduce the cooling rate. This insulation is selected based on the air temperature and the size of the welded pipes. This paper investigates the dynamics of temperature fields at the stages of heating, temperature equalization and heating using a new technology of welding at low temperatures. The proposed technology eliminates the use of thermal insulation material and allows welding to be carried out automatically.The paper presents a mathematical model that describes the thermal process when performing all welding operations at low temperatures. The model describes the thermal process with and without phase transformation. The well-known method of end-to-end calculation with the introduction of effective heat capacity is used to consider the heat of phase transition in the temperature range. The model also considers the dependence of the thermophysical properties of polyethylene on the degree of crystallinity.The following text presents the results of preheating and temperature equalization calculations for welding polyethylene pipes of the PE 100 SDR 11 brand with a diameter of 160 mm at an air temperature of minus 40 °C. To accurately describe the thermal process of real welding, experimental temperature data was used for parametric identification. It is shown that as a result of preheating and temperature equalization in the weld and thermally affected zones and outside them at a distance of more than 10 mm, the temperature values do not exceed acceptable limits. The resulting temperature distribution allows heating according to the standard welding mode. Calculations show that when the heating is completed, the volume of the polyethylene melt corresponds to the volume of the welding melt at the allowed air temperature.These findings can be used to develop a technique for controlling the movement of the crystallization front during welding at low temperatures.

Thermal performance analysis of magnetohydrodynamic Al[formula omitted]O[formula omitted]-SiO2-TiO[formula omitted]/water ternary hybrid nanofluid in converging and diverging channels with nanoparticle shape effects

Improving heat transfer in thermal systems is critical to achieving better results in a variety of systems. The study aims to investigate the laminar flow dynamics of Al2O3-SiO2-TiO2/water hybrid nanofluids, emphasizing how the channel geometry affects the velocity, temperature distribution, and heat transfer efficiency. This understanding is crucial for optimizing industrial processes, such as cooling systems and heat exchangers. Effects of various nanoparticle shapes, joule heating, viscous dissipation, thermal radiation, and heat source/sink on the system’s behavior are evaluated. Governing partial differential equations are transformed into ordinary differential equations using similarity variables and are solved semi-analytically via the homotopy analysis method. As the Hartmann number increases from 1 to 7, the heat transfer rate rises from 0.02% to 0.9%. When the radiation parameter and Eckert number are varied from 0.05 to 0.2, the heat transfer rate increases significantly, from 1.2% to 4.86% and 3.43% to 13.73%, respectively. Heat transfer rate increased by 16.28% with heat source (Q=2) and decreased by -16.12% with heat sink (Q=−2). Platelet-shaped nanoparticles demonstrate lower skin friction in divergent channels, whereas spherical nanoparticles exhibit higher skin friction; this trend reverses in convergent channels. Suspensions of nanoparticles with a 5% volume fraction achieve heat transfer rates of 1.88%, 4.07%, 10.54%, 19.20%, and 8.74% for spheres, bricks, cylinders, platelets, and blades, respectively. The study reveals that Al2O3/H2O, Al2O3-TiO2/H2O, and Al2O3-SiO2-TiO2/H2O nanofluids have the best heat transfer rates for mono nanofluid, hybrid nanofluid, and ternary hybrid nanofluid by 15.24%, 19.92%, and 19.20%, respectively. Finally, multiple linear regression is employed to analyze the impact of relevant parameters on heat transfer rate and skin friction.