Thermal Mode Research Articles

The upward displacement of molten fuel material (or actinides) from the core region due to a reactor-scale fuel bubble expansion–compression, during energetic core disruptive accident (CDA), is essential in evaluating the accident source term for a pool-type sodium fast reactor (SFR). A numerical model is developed to estimate the molten fuel mass distribution in the reactor vessel at the end of the fuel bubble’s expansion–compression phase. The model evaluates the Lagrangian trajectories of representative fuel droplets during the upward displacement from the damaged core. Subsequently, the fuel mass removed from the core region, the fuel mass absorbed by the sodium pool, and the fuel mass that remains in the bubble region after the cessation of the bubble’s expansion–compression cycles are estimated. The fuel droplet diameters are evaluated by considering both mechanical and thermal modes of fragmentation. The initial fuel bubble temperature ranges from 4200 to 4700 K, and the fuel bubble mass is between 1000 and 3000 kg. These values are typical for a medium-sized pool-type SFR under energetic CDA conditions. The fuel droplet trajectories are evaluated by considering drag and gravity as dominant forces under a dilute flow regime. The local fluid (fuel vapor) velocity required to evaluate droplet trajectories is supplied by a fuel bubble model, which accounts for sodium entrainment and the fuel–sodium heat transfer. Analysis results show that the fuel droplet diameter strongly depends on the initial fuel bubble temperature, and it is insensitive to the fuel bubble mass. Also, the sodium entrainment in the bubble region retards the fuel droplet absorption by the sodium pool. Fuel droplets generated by mechanical fragmentation are effectively removed from the bubble region by gravitational settlement. Similarly, inertial impaction effectively removes the thermal fragmentation–generated fuel droplets from the bubble. Results show that the fuel droplets with diameters less than 3 µm (up to 183 kg) remain suspended in the fuel bubble region at the end of the bubble expansion. These suspended fuel droplets can reach the cover gas space during the subsequent buoyancy rise of the fuel/sodium vapor bubble swarm. Results form the basis for the estimation of the accident source term in a reactor containment building due to the fuel bubble phenomenon under energetic CDA in a pool-type SFR.

A rigorous formalism is presented for the time-averaged acoustic radiation force on a spherical particle near an infinite planar boundary subjected to a plane wave. The background medium is assumed to be a weakly thermoviscous fluid, with the viscous and thermal boundary layers much smaller than either the acoustic wavelength or the particle radius. The total acoustic field, composed of the incident, scattered, and reflected fields, is derived using the finite series expansion theory and the image method. Based on the approximate solution to the governing equations of acoustic pressure, velocity, and temperature, we analyze the vorticity mode, the acoustic mode, and the thermal mode in the surrounding fluid, further yielding the boundary conditions at the surface of rigid or nonrigid particles from continuity of velocity. Subsequently, the radiation force function in terms of scattering coefficients is obtained neglecting the contributions of the acoustic streaming effect, followed by a variety of numerical examples. A significant deviation of the force function curves from the ideal-fluid results occurs especially at low reflection coefficients and high incident frequencies. In the Rayleigh frequency range, the first three terms are sufficiently accurate to describe the radiation force, with the critical value of dimensionless frequency decreasing along with the boundary layers. Potential applications include the development of acoustic tweezers involving precise manipulation of microparticles in a bounded and nonideal fluid.

This study addresses a persistent problem in high-cycle fatigue life prediction, observed growth-rate scatter under nominally similar ΔK and R conditions due to extrinsic shielding that varies with temperature. The purpose is to quantify how temperature-dependent crack closure and crack bridging relate to long-crack growth and how temperature level and within-cycle thermal range moderate these effects. Using a quantitative, cross-sectional, case-based design, we assembled a harmonized multi-case dataset and a structured literature corpus, reviewing 45 peer-reviewed papers to shape measurement rubrics and model specification. The empirical sample comprises enterprise-grade component cases from aerospace and power contexts with constant-elevated and cyclic temperature histories. Key variables include log(da/dN) as outcome, fracture-mechanics covariates ΔK, R, frequency, environment, surface finish, microstructure, temperature descriptors mean T, thermal mode, ΔT for cyclic cases, and mechanism indices for closure and bridging scored on five-point scales. The analysis plan applies hierarchical multiple regression with robust errors, entering controls, then mechanism indices, then prespecified moderation terms Temperature × Closure and Temperature × Bridging, with auxiliary ΔT terms for cyclic cases; robustness includes leave-one-case-out checks and an effective-range sensitivity using ΔKeff when opening fractions are available. Headline findings show ΔK and temperature are positively associated with growth, closure and bridging are protective with closure larger in magnitude, and temperature attenuates closure’s protection, ΔT raises growth and further erodes closure under cyclic service. Implications are practical, incorporate temperature mode and mechanism ratings into inspection planning and damage-tolerance models, report ΔK alongside mechanism indices or ΔKeff, and stratify assessments by thermal regime and environment.

Effective thermal regulation is increasingly vital in numerous technological applications. The recent progress on topological diffusion in thermal materials offers promising potential. A distinct feature of diffusive systems is that their anti-Hermitian characteristics ensure purely imaginary eigenvalues representing decay rates, where higher decay rates imply better heat dissipation efficiency. Although research on higher-order topology has been extensive across various systems, investigations specifically of diffusive systems are just beginning. In particular, the few studies on the corner states are limited in their controllability. In this Letter, inspired by the concepts of the atomic p orbital and higher-orbital topology, we introduce multipolar thermal modes in the domain wall between two thermal kagome lattices to achieve multiple corner states. Diverging from traditional research on kagome lattices, we discovered higher-decay-rate corner states above the third band and linked their properties to multipolar modes localized at the domain wall. This approach not only enables higher-decay-rate corner states but also explores new dimensions of control over them. We theoretically identify and experimentally observe various corner states in a two-dimensional diffusive system. It is also demonstrated that simple thermal pulses can trigger transitions between different corner states, thereby dynamically enhancing the decay rate. This study further reveals the potential of topological approaches in heat dissipation, paving the way for the development of thermal management and related fields.

Ultra-pulse fractional CO2 laser is regarded as an effective modality for treating atrophic acne scar. In this study, we described a novel 4-step treatment approach, which combined a manual fractional thermal contraction technology (MFTCT) and ablation mode of conventional CO2 laser, with deep and superficial mode of fractional laser for treating atrophic acne scars. This study evaluated the efficacy and safety of the novel 4-step treatment using the ultra-pulse fractional CO2 laser in patients with atrophic acne scars.20 patients with Fitzpatrick skin type III-IV and facial acne scars were treated with 4-step treatment approach. All patients completed 6 treatment sessions at 8-week intervals. Two blinded dermatologists evaluated the pre- and post-treatment photographs with a 4-point global assessment scale and ECCA grading scale (échelle d'évaluation clinique des cicatrices d'acné). Patients also provided self-assessment of satisfaction and adverse effects.Three of 20 patients showed more than 75% improvement, 14 patients showed 51%-75% improvement, and 3 patients showed 25%-50%. The mean ECCA scores decreased from 109.75 ± 15.26 to 58.75 ± 17.08, with an improvement rate of 46%, and the change was significant (P < 0.01). All patients were either "very satisfied" or "satisfied" with the outcome of the treatments. There were no obvious adverse events after treatments. Only one developed post-inflammatory hyperpigmentation (PIH) for 3 months after the last treatment.This 4-step treatment is an effective and safe treatment modality for atrophic acne scars with an excellent cosmetic outcome and low complication rates.

Abstract Thermal deformation is a critical issue in thin-walled and plate-like structures. Accurate real-time sensing of thermoelastic displacement fields in such structures is essential for ensuring dimensional stability. However, existing shapesensing techniques are primarily designed for mechanically induced displacements and often fail when thermal loads dominate. To fill this gap, this paper proposes a dedicated sensing approach for structural thermoelastic displacement fields by cooperatively fusing prior knowledge with limited measurement data. First, starting with finite element modeling, the superposition principle of structural thermal responses is theoretically derived. Then, an estimator based on thermal mode superposition is presented to simultaneously recover the temperature, thermoelastic displacement, and thermal strain fields from limited sensor data. Finally, a cooperative measurement strategy based on hybrid modes is proposed, enabling multiple sensors to work together in field reconstruction. Simulation and experimental case studies on cantilever plates validated the underlying principles, demonstrating that the proposed estimator not only replicates the accuracy of finite element analysis but also achieves a fourfold improvement in computational efficiency. Moreover, its results show good agreement with measured data. Additionally, the paper compares the performance of different thermal mode construction methods, offering new insights with significant guiding value for engineering applications.

Gas coolers are critical elements of turbogenerator cooling systems, which ensure the reliability and stability of the thermal mode of high-power electric machines. The aim of this research is to improve the accuracy of thermal calculations of gas coolers by combining analytical methods with numerical CFD-modeling (Computation Fluid Dynamics). The cooler’s total cooling capacity is approximately 3.8 MW, distributed across three identical sections.An analytical calculation of heat transfer for a hydrogen-water gas cooler with finned tubes was performed, using classical dependencies to determine the heat transfer coefficients and pressure losses. The results were verified using three-dimensional CFD-modeling of the hydrogen flow through the cooler using the standard k-ε (k-epsilon) turbulence model. The discrepancy between the results of analytical and numerical calculations is less than 10%. The temperature of the cooled hydrogen at the outlet meets the design requirements (+40 °C); however, areas of uneven temperature distribution were identified that require further design optimization. The study introduces, for the first time, a combined approach using analytical calculations and CFD by thoroughly evaluating the heat exchange between the cooling tube fins and hydrogen. This scientific solution enabled the simulation of hydrogen flow within the multi-stage cooler system. The proposed method has proven to be reliable and can be applied both at the design stage and for the analysis of upgraded cooling systems of turbogenerators.

Thermal stimulation represents an effective method for enhancing reservoir permeability, thereby improving geothermal energy recovery in Enhanced Geothermal Systems (EGS). The phase-field method (PFM) has been widely adopted for its proven capability in modeling the fracture behavior of brittle solids. Consequently, a coupled thermo-mechanical phase-field model (TM-PFM) was developed in COMSOL 6.2 Multiphysics to probe thermal fracturing mechanisms in reservoir rocks. The TM-PFM was validated against the analytical solutions for the temperature and stress fields under steady-state heat conduction in a thin-walled cylinder, three-point bending tests, and thermal shock tests. Subsequently, two distinct thermal fracturing modes in reservoir rock under high-temperature conditions were investigated: (i) fracture initiation driven by sharp temperature gradients during instantaneous thermal shocks, and (ii) crack propagation resulting from heterogeneous thermal expansion of constituent minerals. The proposed TM-PFM has been validated through systematic comparison between the simulation results and the corresponding experimental data, thereby demonstrating its capability to accurately simulate thermal fracturing. These findings provide mechanistic insights for optimizing geothermal energy extraction in EGS.

Calculation and Testing of Thermal Modes of the Collet Input of the NUCLOTRON Magnetic Kicker

W–Ni–Fe alloys are widely used tungsten alloys, with laser powder bed fusion (LPBF) emerging as a promising method for producing high-quality components. Thermal input modes significantly influence LPBF component quality, yet their effects on forming quality, mechanical properties, and corrosion behavior in tungsten alloys remain underexplored. This study evaluates three thermal input modes—subarea distributed, long-range quasi-steady, and continuous repeated—on the forming quality, mechanical properties, and electrochemical corrosion behavior of 93 W alloys fabricated via LPBF. The relationships between the thermal input mode and surface morphology, densification, microhardness, compressive properties, and corrosion resistance were analyzed. The subarea distributed heat input mode proved optimal, achieving the highest density (98.7%), microhardness (520.24 HV0.2), ultimate compressive strength (2526.31 MPa), and elongation at fracture (33.61%). The specimens manufactured using this optimized mode exhibited superior corrosion resistance, characterized by the highest corrosion potential (−548.3 mV) and the lowest corrosion current density (2.165 μA cm2). In contrast, the continuous repeated heat input mode led to the lowest forming quality and mechanical properties due to higher porosity (0.27%) and more pronounced metallurgical defects, resulting in reduced compressive strength (2025 MPa) and corrosion resistance. The long-range quasi-steady mode showed intermediate performance between the two. This research clarifies the mechanisms by which the thermal input mode impacts metallurgical defects, mechanical performance, and corrosion resistance, offering valuable theoretical insights into the development of high-performance tungsten alloy components in laser additive manufacturing.

In applications where gearboxes operate under conditions that do not permit the use of liquid lubrication, solid lubrication is necessary to reduce friction and wear. However, the capacity of solid lubrication for convective heat removal is limited, increasing the risk of thermal failure modes. Molybdenum disulfide (MoS2), a solid lubricant used in lacquers, powders, or physical vapor deposition (PVD) coatings, reduces friction and wear, but its use has been limited to low mechanical loads. This study investigates the potential of triboactive coatings, with the incorporation of the triboactive elements Mo, W, and S in wear-resistant CrAlN coatings, to enable the in situ formation of solid lubricants in highly loaded cylindrical gear contacts. Different coating architectures are developed and evaluated through tribological testing. The reduction in friction caused by the in situ formation of solid lubricant is demonstrated using a pin-on-disk and twin-disk tribometer, and validated for cylindrical gears using a back-to-back gear efficiency test rig. Investigations on the influence of the gear geometry also show potential for reducing frictional heat and improving convective heat transfer.

Introduction. The results of studies conducted in 2022…2023s on the fruits of apple varieties of different ripening periods: summer – Williams Pride and Melba, autumn – Gala, winter – Jonathan have been presented. The objects of the study were pomace from the fruits of zoned varieties. The goal of the research was to determine the optimal modes of processing apple pomace into puree products, allowing to achieve the maximum content of pectin substances.The methods. The influence of the thermal action mode (70°C, 75°C, 80°C, 85°C) of apple pomace on the paste quality, as well as the duration (180…210 min) of processing was studied. A 5% sulfurous acid solution was used to accelerate the process of protopectin conversion to soluble pectin. The content of soluble pectin and its molecular weight were determined in the pomace.The results. It has been found that when the temperature reaches 75°C, the content of soluble pectin in the pomace of autumn variety samples reaches 66.9…67.2% after 180…210 min. It has been noted that pectin substances better retain their molecular weight and have better conditioning properties of the paste if the pomace processing period lasts 180 min. It has been found that limiting the processing time of the pomace to 15 minutes at 75°C leads to a reduction in soluble pectin and a decrease in the quality properties of the paste. Thus, the most optimal processing time for the pomace of autumn-ripening apple varieties is 180 minutes at 75°C. The pomace that underwent heat treatment at 85°C contains the same amount of soluble pectin as the samples treated at 75°C for 120 minutes.The conclusion. An increase in temperature leads to a decrease in the molecular weight of pectin substances. In the pomace of summer varieties, the process of protopectin destruction and soluble pectin accumulation during treatment with sulfurous acid occurs more actively at a temperature of 75°C for 90 minutes, while at a temperature of 85°C this process is completed in 60 minutes.

The Casimir effect, originating from quantum and thermal fluctuations, is well known for inducing forces between closely spaced surfaces. When these surfaces are optically anisotropic, these interactions can produce a Casimir torque that rotates the surfaces relative to each other. We investigate, for the first time, the influence of thermal fluctuations on the Casimir torque between birefringent plates. Our results reveal that thermal modes significantly diminish the torque, with reductions up to 2 orders of magnitude for highly birefringent materials. Temperature is also shown to alter the angular dependence of the torque, significantly deviating from the typical sinusoidal behavior, and becomes particularly important at large separations that exceed the thermal wavelength. Finally, we demonstrate that systems of dissimilar birefringent plates that exhibit a distance-dependent reversal in the torque's directions can enable precise control of the torque's magnitude and sign through temperature manipulation. These findings advance our understanding of quantum and thermal fluctuation interplay and provide a framework for designing innovative nanoscale sensors and devices leveraging Casimir torque phenomena.

Dynamic characteristics of subcritical circulating fluidized bed boiler in banked fire thermal standby mode

The article addresses the problem of determining the permissible long-term load for power transformers while considering their thermal regime. The relevance of this work is due to the high level of physical wear and tear on transformer equipment and the need to improve its operational reliability. Exceeding the temperature of windings and oil accelerates insulation aging, necessitating the development of methods to predict the thermal state of transformers. The purpose of this work is to develop a methodology for determining the permissible long-term load of a transformer depending on ambient temperature. The scientific novelty lies in the development of an approximate model of the thermal operating mode of a power transformer, allowing for the prediction of element temperatures and permissible loads. Materials and methods. Research methods include mathematical modeling using Newton – Rikhman equations to describe heat exchange between thermally homogeneous elements of the transformer. The fourth-order Runge – Kutta method with a time step of 30 seconds was used for numerical solution of the system of differential equations. Calculations were performed using author-developed programs in Python with Numpy and Matplotlib libraries. A comparative analysis of simulation results with experimental data from open sources and GOST 14209-85 requirements was conducted. Results. A mathematical model is proposed, treating the transformer as a system of three thermally homogeneous elements – the core, windings, and oil – with heat exchange described by Newton – Rikhman equations. Equations are obtained that make it possible to determine the steady-state temperature of transformer elements and the maximum allowable load factor, taking into account the limitation of the temperature of the winding and oil, the set ambient temperature and the load factor. Approximate formulas were obtained for determining the volumes and contact surface areas of transformer elements based on a calculation scheme. Ratios are presented that allow these values to be estimated approximately depending on the rated power for geometrically similar transformers. It was shown that the heat transfer coefficient between the oil and the environment has the greatest impact on the thermal regime. A condition for the permissible operation of the transformer was formulated, taking into account the required load level and ambient temperature. Simulation results were validated by comparison with experimental data. Conclusions. A mathematical model of the transformer’s thermal regime has been proposed, taking into account the inertia of temperature changes in its thermally homogeneous elements. The influence of the load factor and ambient temperature on the steady-state temperature values of the elements has been determined. A condition for the permissible operation of the transformer has been obtained, ensuring the limitation of winding and oil temperatures.

Automotive transport plays a crucial role in the functioning and development of any country's economy. In Ukraine, it accounts for over half of passenger transportation and three-quarters of freight transportation. A promising development direction is using electric and hybrid vehicles in transportation logistics. It also fosters advancements in battery production technologies, components of hybrid power units, recycling, and the country's transportation infrastructure. Modern vehicle hybridization combines the advantages of traditional internal combustion engines (ICE) and electric drives. The efficiency of hybrid power units can be considered from design and thermodynamic perspectives. The design approach requires the development of new materials and manufacturing technologies, necessitating significant resource expenditures. The thermodynamic approach involves modeling and optimizing thermal processes occurring in the ICE within hybrid power units. The aim of this study is to identify opportunities for improving heat and mass transfer processes in a reciprocating engine to ensure the energy efficiency of a vehicle's hybrid power unit. Heat and mass transfer processes in the ICE are described by a system of differential equations that account for heat transfer in various environments (working gas, cylinder walls, coolant), considering key parameters such as wall temperatures, gas temperatures, heat transfer coefficients, and combustion kinetics. Several scenarios were examined to study the overall heat and mass transfer process. The first scenario assumes constant temperatures of gases and ICE walls, resulting in a steady heat transfer coefficient. The second scenario involves overloading, leading to increased heat loss through the walls and elevated thermal stress on the cooling system. The third scenario considers a decrease in ambient temperature. This study modeled the dependence of engine wall temperatures over time for these three operating conditions, enabling control of thermal modes and prediction of ICE performance to enhance the efficiency of the vehicle's hybrid power unit. It was found that increasing the temperatures of gases and walls affects engine operation duration, the effectiveness of recovered heat utilization, and the optimization of hybrid power unit performance. The more heat recovered during engine operation, the longer it operates with minimal heat loss and maximum efficiency.

ABSTRACT In this study, we examine the thermal instability of magnetohydrodynamic plasma, incorporating factors such as finite electrical resistivity, viscosity, cosmic ray diffusion, and electron inertia, while also considering the effects of partial ionization. Two different dynamics are used for charged fluid and neutral fluid. Through normal mode analysis, we explore linear perturbations imposed on the equilibrium state. The resulting general dispersion relation reveals three distinct modes: the modified Alfvén mode, the infinitely conducting partially ionized thermal viscous mode, and the finitely conducting partially ionized thermal viscous mode. These modes are further analysed in both collisionless and collisional scenarios. We derive approximate instability criteria for various thermal modes and numerically analyse the linear growth rate across different modes to illustrate the impact of the considered parameters on the instability's growth rate. The system's stability is examined using the Routh–Hurwitz criterion, and the stability domains are also discussed. Additionally, the critical wave numbers for isochoric, isentropic, and isobaric modes have been calculated.

If starter culture bacteria are infected with bacteriophages, it results in poor or faulty fermentation of cheese and fermented milk. Despite strict sanitation measures, culture rotation, and special equipment design, bacteriophages with their growing heat resistance remain a serious biotechnological problem for the dairy industry. As a rule, raw milk is the main source of highly mutating bacteriophages with various heat resistance values. Bacteriophages are more resistant to heating than the host strain and most vegetative microbiota; however, scientific publications provide contradicting data on the effect of thermal exposure on lactic acid bacteriophages in various environments. As a result, industrial bacteriophage inactivation requires additional studies to define the most efficient modes. The article introduces the optimal modes of physical bacteriophage inactivation and pasteurization as part of phage monitoring. The authors analyzed available reports on types and groups of lactic acid phages typical of dairy plants, the nature of their heat resistance, and their adaptive evolution to increasing sublethal temperature. The standard methods of analysis and synthesis made it possible to reveal the effect of thermal action on lactic acid bacteriophages in different laboratory conditions. The resulting optimal thermal modes of fermented dairy production may help to develop a system of effective practical antiphage measures that could be compiled into a Program of Preliminary Measures of Phage Monitoring. Although the recommendation for a stricter heat treatment of raw milk does not find unanimous support, dairy plants may apply thermal antiphage inactivation if the processing involves boiling or steaming.

This article considers the improvement of thermal modes of heating of a high-temperature unit, which will allow to increase the efficiency of the technological process and contribute to reducing costs. The topic of studying the modes of heating of high-temperature units is relevant in the context of increasing the efficiency of the production of metal products and reducing production costs. The heat balance of heating the vault of a high-temperature unit was calculated. Based on the results obtained and the presence of excess heat in the profit part, the duration and fuel consumption for a new schedule were selected by calculation. Based on the research conducted, new rational schedules of heating the vault of a high-temperature unit were developed depending on the duration of the schedule and the amount of work performed, which allowed to reduce fuel consumption for heating by 10.7 %–12 %, as well as increase the productivity of the unit due to the sooner entry into operating mode. The results obtained can be used in industry to increase the energy efficiency of the process of manufacturing metal products and reduce the cost of products.

In the era of global climate change, personal thermoregulation has become critical to addressing the growing demands for thermoadaptability, comfort, health, and work efficiency in dynamic environments. Here, we introduce an innovative three-dimensional (3D) self-folding knitted fabric that achieves dual thermal regulation modes through architectural reconfiguration. In the warming mode, the fabric maintains its natural 3D structure, trapping still air with extremely low thermal conductivity to provide high thermal resistance (0.06m2KW-1), effectively minimizing heat loss. In the cooling mode, the fabric transitions to a 2D flat state via stretching, with titanium dioxide (TiO2) and polydimethylsiloxane (PDMS) coatings that enhance solar reflectivity (89.5%) and infrared emissivity (93.5%), achieving a cooling effect of 4.3°C under sunlight. The fabric demonstrates exceptional durability and washability, enduring over 1000 folding cycles, and is manufactured using scalable and cost-effective knitting techniques. Beyond thermoregulation, it exhibits excellent breathability, sweat management, and flexibility, ensuring wear comfort and tactile feel under diverse conditions. This study presents an innovative solution for next-generation adaptive textiles, addressing the limitations of static thermal fabrics and advancing personal thermal management with wide applications for wearable technology, extreme environments, and sustainable fashion.