Calculation Of Temperature Field Research Articles

Analysis of the influence of thermal insulation parameters on the effectiveness of enclosing structures and building heating systems

The results of thermal engineering calculations of external multilayer enclosing structures of buildings and the thermal power of the heating system of residential buildings are presented, including calculations of temperature fields and partial pressures of water vapor at various parameters of structural layers and thermal insulation layers. Variants are considered and an assessment is given of the variation of parameters and the different location of thermal insulation in external multilayer fences for changes in temperature fields and partial pressures of water vapor in the fence, as well as for changes in the thermal power of the heating system of the building premises for two climatological design areas. The calculations were performed according to the methodology presented below using a specially developed computer program.

Inversion Analysis for Thermal Parameters of Mass Concrete Based on the Sparrow Search Algorithm Improved by Mixed Strategies

In the traditional mass concrete temperature field calculation, the accuracy of the thermal parameters is extremely important. However, the actual thermal parameters of mass concrete may have some errors with the laboratory-measured values or specification values due to the site ambient temperature, concrete surface insulation measures, cooling water flow, etc. Therefore, it can be combined with the measured temperature of the field temperature sensors using the sparrow search algorithm (SSA) for the inverse analysis of thermal parameters. Firstly, to address the problem that SSA has low convergence accuracy and easily falls into local optimum, a mixed strategy was adopted to improve the algorithm, including Logistic Chaos mapping initialization of the population, the introduction of adaptive weighting factors, and the use of the Cauchy mutation strategy. Then, the performance test was carried out to compare the performance of the algorithm with three different intelligent algorithms and reflect the superiority of the SSA that was improved by mixed strategies (SSAIMSs). Finally, the proposed method was applied to the thermal parameter inversion of a mass concrete pile cap. The inversion results demonstrated that SSAIMSs can improve the accuracy and speed of thermal parameter inversion, and the calculated results of the thermal parameters and temperatures obtained using the SSAIMSs matched well with the measured results in the field, which can meet the accuracy requirements of the actual engineering.

ТЕОРЕТИЧНЕ ДОСЛІДЖЕННЯ ТЕПЛОВИХ ПРОЦЕСІВ НА ВУГЛЕЦЕВИХ ЕЛЕКТРОДАХ В РЕЗУЛЬТАТІ ДІЇ ПЛАЗМИ ПРИ ГЕНЕРАЦІЇ НАНОСТРУКТУР У ВАКУУМНІЙ ДУЗІ

A mathematical model has been refined to determine the thermophysical and thermomechanical processes on electrodes during the plasma formation of nanostructures. The model takes into account the effects of electrode spots, evaporation, sputtering, and thermal stresses in the electrode bodies. Calculations of temperature distribution on the surfaces of the graphite cathode and anode were carried out, considering the conditions necessary for obtaining nanostructures. An analysis of the thermophysical processes on the surfaces of the graphite cathode and anode during the transition to the working regime was conducted. The stability of the electrodes during plasma generation of nanostructures was determined by changes in the geometry of the electrodes. Calculations of the temperature fields on the end surface of the graphite cathode showed that with a continuous increase in the cathode surface temperature, the nature of its distribution does not change fundamentally. Calculation of temperature fields along the radius of the graphite cathode at different moments in time during the transition to the working regime showed a slight impact of evaporation on the change in the cathode's geometry. Determining the temperature fields along the generatrix of the anode showed the greatest impact of evaporation on the small area of the anode closest to the cathode. The dependencies of the acting stresses on temperature for the graphite cathode and anode were obtained. Studies of the dynamics of changes in thermal stresses on the electrodes during the formation of nanostructures in a plasma environment indicate that the values of thermal stresses are far from the material's strength limit. A theoretical study of the thermophysical and thermomechanical processes on the graphite cathode was carried out and compared with experimental measurements. The calculation of the electrodes' lifespan during the creation of carbon nanostructures in a plasma environment was 2.52∙105 s. The experimental lifespan of the graphite cathode is 2.88∙105 s, which is quite close to the calculated value. The coincidence of the obtained theoretical and experimental results indicates the viability of the developed model. The article may be of interest when designing equipment for obtaining nanostructures in a plasma environment and for further research on the physical parameters of electrodes.

Dynamic numerical calculation of multi-physics fields in IGBT chip layer based on ETM-PINN

The electric-thermal-mechanical (ETM) multi-physics coupling fields commonly exists in power electronic devices such as insulate-gate bipolar transistor (IGBT), which dominates the evolution of key state variables inside the components. Among them, the junction e and electric potential of the chip layer, as the dependent variables of various lifetime physical models, directly affect its remaining service life and health status. Aiming at the problem that the key physical variables inside the IGBT are difficult to monitor and predict, this paper first integrates and establishes the ETM coupling partial differential equations (PDEs) inside the IGBT, then accordingly proposes an accurate numerical calculation method for coupled physical fields based on ETM-physics-informed neural networks (ETM-PINN).Through relevant simulation verification, it can not only realize the numerical calculation of the chip layer junction temperature and electric potential field without data, but also perform multi-physics predictive calculation with reduced accuracy in the absence of the key coefficients in PDEs. In the presence of additional physical field data, it can also perform data-model fusion calculations to further improve the solution accuracy.

Simulation and Calculation of Temperature Field and Current-Carrying Capacity of Power Cables under Different Laying Methods

Precisely determining how cables distribute their current-carrying capacity and temperature field is crucial for the dependable and cost-effective functioning of power grids. Firstly, the power cable structure and the advantages and disadvantages of different laying methods are analyzed in detail. Secondly, the theoretical model of current-carrying capacity calculation and temperature field of power cables, including heat convection, heat conduction, and heat radiation, is constructed, and the method for calculating cable current-carrying capacity, relying on the double-point chordal interception method, is suggested. Then, the COMSOL multiphysics 6.2 finite element simulation software is utilized to create a simulation model that aligns with the real cable laying technique. Finally, the current-carrying capacity and temperature field of power cables are simulated and analyzed for different arrangements of power cables in three laying modes, namely directly buried, row pipe, and trench. The simulation results show that the cable laying method greatly affects the cable’s carrying capacity; the more centralized the cable distribution, the smaller the flow. The method can be realized in different ways of laying power cables in the real-time rapid calculation of flow as the actual laying of power cables has an important reference and reference significance.

Parameter optimisation of the ventilation system for an underground power space using a hybrid model

The ventilation system is one of the essential safety systems in underground power spaces. Over the years, active ventilation has been widely employed for heat dissipation in underground power spaces. In operation, high-power equipment generates significant heat, necessitating sufficient heat dissipation for smooth and efficient functioning. The effectiveness of the ventilation system is influenced by airflow, making aerodynamics a crucial aspect of studying underground power spaces. This study establishes a comprehensive hybrid model (a combination of physical and data-driven models) representing underground power spaces. Ansys Fluent and MATLAB are used to simulate and calculate temperature fields for various structures. The physical model employs model order reduction to achieve efficient computation without compromising accuracy. For the data-driven model, a genetic neural network is developed for multifactor nonlinear optimisation to evaluate and analyse thermal behaviour within the space. The integrated hybrid model enables efficient and high-precision calculations for the underground power space’s ventilation system. The research outcomes provide a theoretical foundation for practical construction and design schemes of underground power spaces, contributing significantly to ensuring their safety and optimal functionality in real-world applications.

Electrothermal coupling analysis of submarine cables

ABSTRACT With offshore wind power transmission engineering development, submarine cable laying plays an important role in energy supply. Deep-water heavy-current composite submarine cables generate heat during power transmission, which raises their temperature and impacts energy efficiency and mechanical properties. To address the issue of heat release affecting structural sections during cable operation, a structural temperature field calculation theory is introduced, establishing a method for calculating the temperature field of submarine cables.The IEC standard's equivalent thermal circuit method and COMSOL Multiphysics' electromagnetic, thermal coupling method were employed to assess the current carrying capacity at the insulation temperature. The finite element model's accuracy was confirmed by comparing manufacturer-provided parameters. Additionally, a 3D finite-element model of the cable was created to determine its tensile, bending, and torsional stiffness with and without the electric-heat-force field coupling.

Analysis of a plasma reactor performance for direct nitrogen fixation by use of three-dimensional simulations and experiments

This study utilizes state-of-the-art in-situ measurements and advanced three-dimensional simulations to investigate the operation of a microwave plasma reactor for nitrogen fixation at a high subatmospheric pressure under various power inputs. It is shown that the system should be treated as a warm plasma due to negligible differences in vibrational and rotational temperatures and that it is required to account for chemical non-equilibrium. Complex flow field and significant temperature and concentration gradients are observed, emphasizing the need for three-dimensional simulations to accurately describe the interactions between mass, heat, and momentum transport and chemical reactions in non-equilibrium conditions. The innermost plasma regions reach temperatures close to 6000 K, while wall temperatures remain low due to presence of a low-temperature swirling flow field around the hot core. Analysis reveals that the swirling flow field around the hot core provides intrinsic partial quenching in regions with large temperature gradients which counteract the return to chemical equilibrium and enrich the flow surrounding the hot core. The inner flow exhibits a recirculation zone, stagnation point, and a transition into an increasingly parabolic flow profile closer to the reactor outlet. The agreement between the numerical modeling and the measurements is strong. In-situ Raman spectroscopy measurements confirm the calculated temperature field inside the reactor. Thermocouple measurements on the reactor wall are also in good agreement with the simulation. Additionally, Fourier-transform infrared spectroscopy measurements agree very well with the simulated amount of nitrogen oxide exiting the reactor at different microwave power inputs. The understanding and modeling capabilities are expected to support the development of future reactor designs that can facilitate higher yields.

Research on thermal characteristics of double-nut ball screw

Abstract Preload, external load, and feed speed have significant effects on thermal characteristics of ball screws. In this paper, ground on friction heat generation theory and Hertz contact theory, a thermodynamic modeling of the double-nut ball screw is established, heat generation under different preload forces and feed speeds is analyzed, and temperature field is estimated based on finite difference method. The results show that preload and feed speed have a obvious impact on screw nuts temperature. The finite difference method makes numerical calculation of temperature field more convenient.

Effect of Scanning Strategies on Grain Structure and Texture of Additively Manufactured Lattice Struts: A Numerical Exploration

Electron beam powder bed fusion (PBF‐EB) is a promising technology for fabricating complex parts with near‐net‐shape precision. Moreover, PBF‐EB offers a unique opportunity to tailor the microstructure, thereby tuning local mechanical properties. Numerical simulation has emerged as a powerful tool for predicting the evolution of texture and grain structure during PBF‐EB. Herein, the in‐house developed and experimentally validated simulation software, , is employed to investigate the impact of scanning strategy on the texture and grain structure of CMSX‐4 in PBF‐EB‐processed thin tilted lattice struts, commonly found in cellular structures. The core of consists of a finite difference solver for temperature field computation and a cellular automaton model for simulating grain structure evolution. Nine distinct scanning strategies are systematically explored. The resulting texture and grain structures are meticulously compared and comprehensively discussed. Notably, the contour scanning strategy yields distinctive texture and grain structures compared to other explored scanning strategies. This study highlights the capability of in assisting microstructure customization in the PBF‐EB process, and advances the understanding of the relationship between PBF‐EB scanning strategy and resulting microstructure in tilted lattice struts.

A temperature field model based on energy flow analysis of wet clutch sliding interface

A fluid-solid convective heat transfer model is constructed according to the velocity distributed calculation of lubricant in clutch groove cavity. Considering the characteristics of circumferential alternation of heat dissipation and generation area on separator plate surface,the effective energy flow characterization equations of convective hear transfer and heat generation at sliding interface are established. The non-heat source temperature field is proposed by effective convective heat transfer and heat conduction. Following the target constraint of continuous contact temperature, the temperature field change is solved during actual dynamic heat flux partition period. The tests with different intensity of heat generation and dissipation are designed, which indicates the reliability of model. The research provides a new method for the temperature field calculation of clutch.

A two-phase flow node-solid joint simulation algorithm based on heat flow correction

In order to accelerate the temperature field calculation of fuel and tank wall protective materials, we propose a node-solid joint simulation method based on heat flow correction, in which the gas–liquid is used as a node for joint CFD (Computational Fluid Dynamics) calculation of the solid temperature field. Based on this method, we constructed a transient thermal analysis model of the fuel tank and performed a gas–liquid–solid conjugate heat transfer tight coupling simulation to obtain the wall heat transfer coefficient and the corrected heat flux under the specified thermal boundary conditions. The results show that the maximum relative errors of the average temperature of the gas–liquid node and the temperature field of the tank wall are less than 0.2 % and 6 %, respectively, and the calculation efficiency is about 160 times that of the traditional tight coupling calculation. When the solid boundary temperature is reduced by 200 K and increased by 500 K, the maximum relative error between the average temperature of the gas–liquid node and the solid temperature is less than 7 %. The algorithm has good robustness and accelerates the iterative design of the fuel tank. The accuracy of the algorithm was verified by the fuel temperature test experiment of the full flight profile.

Modified reconstruction of boiler numerical temperature field based on flame image feature extraction

ABSTRACT Computational fluid dynamics (CFD) method is a common method to obtain the temperature field distribution within the furnace. However, in order to reduce computational complexity, the numerical simulation involve simplifications in boundary conditions and model parameters. As a result, the temperature field distribution deviates from the actual operating conditions. This paper proposes a numerical temperature field modification method based on flame images. Flame images corresponding to the operational conditions are collected using the Industrial Flame Monitoring System (IFMS). The flame images are preprocessed, and the contour of the flame’s core region is extracted using the Mask Region-based Convolutional Neural Network (Mask R-CNN) method. The geometric features of the flame are extracted, and matrix calculations are applied to modify the numerical temperature field. The modified temperature field exhibits a deviation in the combustion center, aligning with the actual operation of the boiler. A comparison between the modified temperature field and the temperature measurements from flue gas shows consistent temperature trends. The absolute error (AE) under different operating conditions is under 8.8 K, and the relative error (RE) remains below 1.3%. The analysis results demonstrate that it can enhance the accuracy of temperature field calculations by the modification from flame image features.

Solar radiation visibility testing algorithm for precise shadow distribution for spatial steel structural thermal analysis under sunlight

As a large-span spatial steel structure, the radio telescope, characterized by its extensive span and numerous structural components, is sensitive to temperature gradients and susceptible to localized deformations induced by non-uniform temperature filed under sunlight, thereby affecting the operational performance. In order to calculate the shadow distribution of the structure, this study proposes a solar radiation visibility testing algorithm based on the depth buffer. To validate the accuracy of the proposed algorithm, the shadow distribution of a shading device is calculated employing the new algorithm, theoretical methods, and Ladybug tools. The results show that the shadow distribution obtained by the three methods is consistent. The thermal numerical simulation of the grid structure using the direct solar radiation calculated by the proposed algorithm is compared with the experiment results, and the error is below 5 %. Taking a radio telescope as an engineering application, the temperature distribution and pointing accuracy under solar are calculated. 9:00 and 16:00 have the worst pointing accuracy, while 11:00–13:00 has the best pointing accuracy. This study can provide a reference for the calculation of temperature field of spatial steel structure which is sensitive to sunlight temperature.

Effects of Multispectral Absorbing Coating on the Generated Voltage of Solar Radiation–Thermoelectric System

The effective utilization of solar energy is an important development direction to realize the exploration of clean energy. Herein, a model of solar radiation–thermoelectric generation (TEG) system is established, which is composed of solar absorbing coating and TEG component. Five different microscopic structures of coating are designed and the spectral absorption properties are numerically analyzed with the finite‐difference time‐domain method. Then, the absorbed solar energy and produced open‐circuit voltage with different coating structures are compared, with the coupling calculation of temperature field and electromagnetic field achieved. Additionally, the effects of structural size parameters on the output voltage performance are discussed. It can be observed that the absorbing coating can effectively improve the performance of TEG component, and the multilayer structure with appropriate gold particle diameter chosen is an optimization research direction for more efficient energy conversion.

Review on convective and radiation heat transfer between bridges and external environments

The heat exchange between bridges and external environments is the primary cause of the temperature effect on bridges. The complexity of the two-phase (gas–solid) heat transfer mechanism, the diversity of the surface characteristics of bridge materials, and the uncertainties of the environment in which bridges are located make the numerical calculation of the heat exchange between bridges and external environments difficult. Several studies have been conducted by scholars around the world. In this work, the research on convective and radiative heat exchange between bridges and external environments is surveyed, analyzed, and summarized. The influencing factors and calculation methods of bridge temperature are examined, and the convective heat transfer and radiation mechanisms, theoretical calculations, and experimental measurement methods used to investigate the relation between bridges and external environments are summarized and analyzed. The value determination methods for convective heat transfer and radiation absorption coefficients in the calculation of the bridge temperature field are summarized. In addition, the problems and shortcomings of current research are evaluated, and future research directions are identified and discussed.

Nonlinear coupled multi-physics field analysis of permanent magnet synchronous motor combining finite element analysis with optimized meshless method

Aiming at significant disadvantages of finite element analysis (FEA) performed in coupled multiphysics field calculation, including high computing cost and strong dependency on meshing quality. Taking a high-speed permanent magnet synchronous motor (P MSM) as an example, an approach combining FEA with optimized meshless method is proposed to solve the heat transfer problem. Firstly, electromagnetic losses under rated and 1.2 times overloaded operation conditions are calculated using FEA respectively. Secondly, three-dimensional FEA flow models considering the influence of viscosity varying with temperature are established. Thirdly, convective heat transfer coefficients are calculated as the boundary condition, after which the electromagnetic losses as heat sources are mapped to the threedimensional steady-state temperature field calculations using FEA and conventional meshless method respectively. Applying the above two methods, a singular boundary method (SBM) is employed to replace the temporal derivative term of the transient calculation equation. Finally, to mitigate the illconditioned matrix appearing in the conventional meshless method coupled with FEA, an optimized meshless method is proposed to recalculate the heat transfer equation. After that, the calculation results of the above methods are compared with experimental results. This research is beneficial for the multiphysical coupling analysis of electrical equipment with complex structures considering nonlinear factors.

Microstructural evolution modelling and low-stress fatigue performance of bimodal-structured Al-Mg-Sc-Zr alloy produced by laser powder bed fusion additive manufacturing

ABSTRACT Coarse – and fine-grained bimodal-structures in a Al-Mg base alloy with rare earth elements of Sc/Zr is produced due to the ultrafast nonequilibrium solidification occurs in laser-induced molten pools during laser powder bed fusion (LPBF) additive manufacturing. A novel high-fidelity cellular automaton (CA) algorithm incorporating numerical calculations of molt-pool temperature fields elucidates the formation and evolution of the bimodal-structure. Subsequent heat treatment induces precipitation of Al3(Sc/Zr) particles within the grains, synergistically enhancing strength and plasticity of the LPBF-processed alloy. The crystal plastic finite element method (CPFEM) is used to reveal the synergistic effect between the strength and plasticity during the material tensile procedure. The bimodal-structure exhibits good fatigue resistance but intriguing anisotropy under low stress cyclic loading. It is proved that differentiated distribution patterns relative to the principal stress direction of the bimodal-structure have a significant influence on its fatigue performance. Numerical evolutionary of the bimodal grain deformation reflects this phenomenon.

Construction alignment and closure control of CFST truss arch bridges based on temperature effect

To reveal the temperature deformation laws and achieve the accurate alignment prediction during the installation process of long-span concrete-filled steel tubular arch bridge ribs in complex environments, this paper establishes a three-dimensional refined heat transfer model for temperature field and effect calculation of truss arch ribs. The model uses the Ray Tracing Technology to recognize the member-caused-shading area on arch ribs. And by comparing with the actual measurement results and shadow effects to achieve the accurate calculation of temperature field. Finally, the variation of ribs deformation during construction and the optimal closure time are detailed analyzed. Results show that the computational method used in this paper can achieve accurate recognition of shadows and precise calculation of the complex three-dimensional temperature field of truss arch ribs. After considering the shadows, the maximum temperature difference between the upper chord sunshine area and lower chord shadow areas can reach 25 °C, which is significantly greater than 8 ℃ in the "Specifications for design of highway concrete-filled steel tubular arch bridge" (JTG/T D65–06-2015). Due to the solar incidence variation along the longitudinal direction of the arch ribs, extreme temperature fluctuation of the chord tubes occurs, with a maximum temperature difference of 21 °C. When arch ribs reach the maximum cantilever, the daily vertical displacement variation can reach approximately 87 mm, and the maximum displacement difference between arch ribs of two canyon sides can reach 15.6 mm at the same time. The solar-caused maximum compressive stress is 34 MPa, which can exceed 100 MPa after superimposing the gravity and cable effects. Based on the analysis of the displacement of both sides of the closure joint under the influence of sunlight, this paper identifies the window period for the closure control of the long-span steel truss arch ribs, laying the foundation for the accurate control of the rib construction alignment and the closure internal force state.

Temperature field analysis and equal-amplitude temperature rise constraint current control method under open-circuit fault-tolerant operation for five-phase permanent magnet motor

The phase redundancy and freedom of the five-phase permanent magnet motor (FPPMM) enhance the reliability of the motor system. However, the temperature rise and torque reduction issues of the motor during open-circuit fault operation need to be further studied. In order to study the temperature distribution characteristics and the output capability of the motor under fault operation subject to temperature rise constraints, a 3-D global temperature field model containing a complex heat dissipation structure has been established. And the equal-amplitude temperature rise constraint current control method is proposed under open-circuit fault-tolerant operation to improve its output capability. The temperature distribution of the motor during steady state operation under rated operating conditions is analyzed with emphasis. Based on this, the temperature field changes of the motor during single-phase and two-phase open-circuit fault-tolerant operation are investigated. Then, the proposed equal-amplitude temperature rise constrained current method is introduced in detail to ensure the safe operation of the motor. An experimental platform is built, which verifies the accuracy of the temperature field calculation, as well as the correctness of equal-amplitude temperature rise constrained current method.