Simulation Of Thermal Processes Research Articles

Energy-efficient solar heat supply system based on hybrid photovoltaic collector

Following the commitments made under the Paris Climate Agreement, the scientific community has initiated a strategic increase in the share of renewable energy sources while gradually reducing dependence on traditional carbon fuels. Priority is given to the acceleration of the development of the photovoltaic industry, which has shown a constant increase in capacity over the past decades. According to the energy and climate strategies of the European Union, a significant increase in the amount of energy generation due to solar sources is planned. Therefore, the article is devoted to the development of a solar heat supply system based on a hybrid thermal photovoltaic solar collector with an improved design and analysis of the main characteristics of its operation using computer modeling. The authors have developed a 3D computer model of the proposed hybrid system with a solar collector by using SolidWorks software. The change in the temperature of the heat carrier in the hybrid thermal photovoltaic solar collector under constant solar radiation was analyzed. The temperature change of the coolant in the thermal accumulator of the system was also investigated. The results of the simulation of thermal processes revealed the key regularities of the temperature increase during the computer experiment, both in the hybrid thermal photovoltaic solar collector and in the thermal accumulator. The change in the instantaneous specific heat capacity of the developed solar collector was analyzed, and its average efficiency was estimated. The trends of changes in the thermal efficiency of the developed heat supply system during the computer experiment were determined. The novelty of the study is that the design of the hybrid thermophotoelectric solar collector has been improved, its 3D computer model has been developed, and the main thermal characteristics of the developed heat supply system with constant solar radiation have been obtained, which will contribute to the development of calculation methods for such heat supply systems with hybrid solar collectors in the future.

Temperature control by simulated adaptive layer times in powder bed fusion processes

In this work, a simulation-based thermal management model for metal parts produced through powder bed fusion (PBF) is proposed. PBF is an additive manufacturing technique that employs a high-energy beam to selectively melt and fuse powder particles layer by layer. The productivity and efficiency of PBF processes can be significantly increased using multi-laser systems with larger build volumes. However, this approach affects the parts thermal history, which can significantly impact their mechanical properties, microstructure, and defects. To address this issue, an algorithm has been developed to calculate adaptive cooling times reaching predefined temperatures at the end of each layer. The algorithm is used in a fast thermal process simulation using layer lumping. The simulation model is applied to a modern multi-laser machine, and the effectiveness of the adaptive cooling times and minimal layer times is evaluated. The results indicate that lower maximum temperatures can be achieved in less manufacturing time with adaptive cooling times than with minimal layer times. However, the significant increase in manufacturing time highlights the need for active cooling systems to utilize multi-laser machines fully. In summary, this paper presents a significant contribution to the field of additive manufacturing, emphasizing the importance of thermal management in ensuring the quality and performance of metal parts produced through PBF.

Heat transfer in Z-scan experiments

In this study, we present the results of theoretical calculations concerning heat exchange in materials subjected to laser irradiation, with particular emphasis on Z-scan experiments. Using explicit difference methods, we model the temperature distribution in three-dimensional samples of various sizes, such as [4 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 4 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 2] mm, [5 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 5 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 2] mm, and [6 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 6 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 2] mm. The simulations encompass two different types of pulsed lasers with durations of 10 (ns) and 100 (ps), adjusting laser parameters to achieve a peak irradiance intensity of 5 GW/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^2}$$\\end{document}. The temperature distribution in samples, denoted as T(x, y, z, t), is computed using a novel laser heat source model specifically designed for this problem. The computational program Z-lambda enables not only the simulation of thermal processes during the Z-scan experiment but also post-experiment analysis. The development of this software was one of the main objectives of this study. The results indicate that the thermal analysis of Z-scan experiments requires consideration of factors such as laser pulse duration, laser repetition time, sample geometry, and heat exchange between the studied material and the surroundings. Especially in the Z-scan technique, controlling thermal parameters before the experiment is crucial for obtaining precise and reproducible results. It is noteworthy that sample heating during the experiment can significantly influence charge carrier density, subsequently affecting the parameters of nonlinear optics (NLO). Tools like the Z-lambda program allow for the optimization of laser parameters, minimizing sample heating, and reducing the thermal impact on NLO parameters.

Advances in Thermal Process Engineering and Simulation

The integration of theoretical insights and current findings in the articles included in this Special Issue holds the potential to bridge the gap between academic research and real-world challenges in enhancing physical–chemical processes [...]

Numerical simulation of thermal processes in cold metal transfer-based additive manufacturing

Numerical simulation of thermal processes in cold metal transfer-based additive manufacturing

Simulation of thermal processes in a half-space under heating by a moving source with a uniformly distributed heat flow

Using the method of applying instantaneous point sources, a solution was obtained to the problem of heat conduction during surface heating of a body in the form of a half-space by a uniformly distributed highly concentrated heat flux moving at a constant speed along a rectilinear trajectory with a different shape of the heating spot at constant thermophysical characteristics of the material. The effect of temperature loading modes and the shape of the heating spot on thermal processes in the heat-affected zone is studied. The surfaces and lines of the temperature level are constructed for different moments of time and speed loading modes in different planes of the heating zone. Time dependences of temperatures, heating and cooling rates for body points are given. The shortcomings of the methods used for linear thermal conductivity, the lack of direct consideration in the design scheme of the surface melt zone of the material do not allow one to reliably assess the effect of heat treatment modes on changes in material properties, focusing only on the level of the maximum design temperature. In this regard, the structure formation of metal in the zone of thermal action is proposed to be associated with a thermal impulse, i.e. the total thermal energy perceived by the material at a given point of the body, as well as with the effective structurization impulse introduced into consideration, which characterizes the energy spent on the process of structural transformations of the material, and the structurization time at a point and some volume of the body. The dependencies of these values on the speed of movement and the shape of the heating spot are presented. The considered approaches can be applied to various metals and alloys. The research results can be used to develop more effective methods for determining the optimal modes of surface hardening of metal products with a high-energy source.

Modeling of thermal processes in vertical heat exchangers of ground-source heat pump

The basic directions for perfection heat supply systems are the tendency of transition to the low-temperature heating systems based at application heat pump installations. We consider heat supply systems with ground-source heat pump. The paper considers modeling the efficiency of ground-source heat pumps with the account of Ukrainian climate conditions. The paper presents the energy performance criteria which show the way to rational implementation of ground-source heat pumps for heating. A computational model based at non-stationary heat exchange processes in elements of ground-source heat pumps is developed. Generalization and analysis of theoretical and experimental dates allow establishing nature of dependence thermophysical properties on temperature insoil around ground heat exchangers during long term operation of the system. Numerical simulation of thermal processes in vertical ground pipes for ground-source heat pump working with low-temperature heating systems has been worked out. The results of numerical modeling demonstrated perfection and technical adaption of ground-source heat pump for low-temperature heating systems with rational using ground energy potential. The novelty of our method is complex usage theoretical and experimental results which enable to prevent freezing in the ground during long term exploitation This provides insights at effects of different resource mixes and may serve as a new approach to analysis of future heat pump systems using ground source energy development.The proposed method contributes to the field of creation and implementation the sustainable heating technologies using renewable energy sources. The ground heat exchange pipes quantities that are necessary for effective operation heat pump installation, capacity and coefficient of performance with the account of climate conditions are calculated.

Computer simulation of thermal processes involving Sr and Ca radionuclides in the process of heating radioactive graphite in an air atmosphere

The paper presents the results from a thermodynamic analysis of the behavior of Sr and Ca radionuclides in the process of heating radioactive graphite in an air atmosphere. The TERRA software package was used for the thermodynamic analysis in a temperature range of 300 to 3600 K to determine the possible composition of the ionized, gaseous and condensed phases. It has been found that strontium is in the form of condensed SrCl2(c) and gaseous SrCl2 in a temperature range of 300 to 1600 K, and in the form of gaseous SrCl2, SrO, SrCl and Sr and ionized SrCl+, Sr+ and SrO+ when the temperature is increased from 1600 to 3600 K. Calcium is in the form of condensed CaCl2(c), CaUO4(c), CaO(c) and gaseous CaCl2 in the temperature interval between 300 and 2100 K, and in the form of gaseous Ca, CaCl and CaO and ionized Ca+, CaO+ and CaCl+ when the temperature is increased from 2100 to 3600 K. The paper determines the key reactions within individual phases and among condensed, gaseous and ionized phases. The equilibrium constants of their reactions have been calculated. Based on the results obtained, dependence plots are presented for the Sr and Ca radionuclide distribution by phases.

Quality assurance thermophysical aspects of highly porous implants with cellular structure obtained by selective laser melting

Selective laser melting (SLM) is an additive manufacturing process that involves the layer-by-layer construction of a three-dimensional object by local melting of a powder layer based on a prepared CAD model. This technology makes it possible to manufacture products of complex configuration, including internal channels of complex geometry. Such products include personalized highly porous implants, which are subject to very strict requirements in the field of elastic and strength properties, ensuring their compliance with the properties of the biological objects being replaced. The quality of highly porous cellular products formed by the selective laser melting method based on metal powder compositions is determined by a significant number of factors, the combined influence of which is difficult to control. At the same time, the structure and mechanical properties of highly porous cellular materials (HPCM) obtained by laser synthesis are largely determined by the melt bath shape stability, which depends on the ability of local heat dissipation, which in turn is determined by the fused product geometry. Under these conditions, simulation of thermal processes, including the prediction of the part fusion temperature modes, is of paramount importance. This study focuses on the numerical analysis of the powder layer thermophysical parameters during the laser melting process, which is difficult to analyze by direct measurements, and a computational model based on COMSOL Multiphysics has been created to predict the melt bath temperature field. The numerical model made it possible to quantify the influence of the selective laser melting process parameters (laser power and scanning speed) in combination with the choice of material and topology of the part on the temperature fields formation to determine the process technological parameter and the features of creating geometry for additive manufacturing, which make it possible to obtain products of proper quality. Cellular implants based on Ti6Al4V powder have been grown by selective laser melting.

Numerical Simulation of Thermal Processes and the Effect of Heating of Near-Surface Layers of Titanium on the Diffusion Transfer of Dopants during High-Intensity Pulsed Ion Implantation

Numerical Simulation of Thermal Processes and the Effect of Heating of Near-Surface Layers of Titanium on the Diffusion Transfer of Dopants during High-Intensity Pulsed Ion Implantation

Improved thermal conductivity parameterization of SHAW model in permafrost regions on the Qinghai-Tibet Plateau

Soil thermal conductivity is critical for determining the hydrological and energy transfer processes in permafrost regions and simulating hydrological and thermal dynamic processes with land surface models. In this study, improved thermal conductivity parameterizations of the Simultaneous Heat and Water model (SHAW) were assessed using observation data from permafrost regions on the Qinghai-Tibet Plateau (QTP). The results indicated that the SHAW could precisely describe soil hydrological and thermal processes at the Tanggula (TGL) site. In general, the performances of Johansen's, Luo's, and the ORCHIDEE-MICT model's soil organic matter (SOM) parameterizations were superior to the original De Vries's parameterization. The SOM parameterization performed the best. The root mean square error (RMSE) of the active layer's soil temperature was 0.42 °C lower than that of the original parameterization at the Xidatan (XDT) site and 0.2 °C lower at the TGL site. In particular, the RMSE of the soil temperature at 3 m depth at TGL was 0.8 °C lower than that of the original parameterization. The average Nash-Sutcliffe Efficiency (NSE) for simulating the active layer soil temperature using the SOM parameterization was 0.915 at TGL site and 0.806 at XDT site. While De Vries parameterization yielded average NSE values of 0.771 and 0.627 for soil temperature simulations at the two sites, respectively. The results indicate that the soil organic carbon cannot be ignored in the simulation of hydrological and thermal processes in permafrost areas with a high soil organic carbon content. Notably, the simulated soil temperatures during the freezing period and the soil liquid water content during the thawing period improved significantly after modifying the thermal conductivity parameterization of SHAW. Therefore, the revised SHAW more accurately reflects the water and heat transfer processes of permafrost and can be used to analyze land-atmosphere interactions.

Acceleration of state–space method based on parallelization for enhancing building thermal process simulation efficiency

Acceleration of state–space method based on parallelization for enhancing building thermal process simulation efficiency

Methods for the quantification of uncertainties in thermo–hydro–mechanical simulations for safety analyses and influence of modelling decisions

Abstract. The simulation of thermal, hydraulic, and mechanical coupled processes can be a decisive factor in the integrity assessment of geotechnical and geological barriers. Modelling decisions, such as the representation of heterogeneity and the constitutive models used, significantly impact the simulation outcome (Wagener and Pianosi, 2019). Furthermore, numerical inputs to the simulation, i.e. material parameters and boundary conditions, are subject to uncertainty. This results in a lower confidence level of the outcome, even if the overall simulation framework is well validated. To derive robust conclusions from such analyses, it is important to quantify the relative impact of modelling decisions and inputs on certain quantities of interest. Parameter uncertainties can be quantified by their forward propagation through the discretized problem (Helton, 1994), providing a natural frame of reference for quantifying structural uncertainty (Bond et al., 2007), such as the representation of heterogeneity, and for model validation. This contribution will focus on the latter aspects. We present research on workflows for the unification of evaluating uncertainty in experimental data and certain modelling decisions. We first focus on parameter uncertainty quantification and the resulting conclusions concerning the chosen modelling approach. Hereafter, scale questions are addressed in the context of heterogeneity and anisotropy, based on selected case studies. We close by discussing two example applications, namely one at the Underground Research Laboratory (URL) scale (Mount Terri Full-Scale Emplacement (FE) experiment) and one at the repository scale (ANSICHT Ton Nord model). This work is done as part of the Bundesministerium für Umwelt, Naturschutz, nukleare Sicherheit und Verbraucherschutz (BGE URS) research cluster.

Modeling and optimal design of liquid cooling system of electronic module

Formulation of the problem. Optimal design of avionics (avionics) structures is impossible without the development of new complex methods for modeling thermal processes in their designs and verification based on the results of a full-scale experiment, as well as the creation of methods for the justified use of existing and creation of new mathematical algorithms for optimization procedures. When designing modern RES, it is important to provide a temperature regime for the functioning of power elements of the equipment, in our case, we will consider an electronic module. To ensure normal thermal conditions, cooling systems are used, most often heat sinks (radiator) are used, but in some cases it is not possible to install it. To solve this problem, it is proposed to develop a liquid and air cooling system for the electronic module using an expanded set of elements of cooling systems, including a submersible cooling system. Purpose. Develop a comprehensive methodology for modeling and optimal design of a liquid cooling system for an electronic module, the reliability of which is confirmed by the results of analytical calculations and experimental data. Results. On the basis of the developed 3D model of the electronic module, the procedures for multivariate analysis of the laboratory stand unit were implemented using modern computer-aided design tools. A mathematical formulation was formed and procedures for optimizing the thermal regime were performed: modeling and optimization of the coolant; block topology optimization; optimization by body material and coolant type. Graphs and tables of simulation results are presented, on the basis of which it is possible to draw conclusions about the influence of a particular parameter on the distribution of heat fluxes. All the difficulties that the authors encountered in the course of design optimization in the modeling environment are described in detail, as well as ways to solve them. Practical significance. The results obtained make it possible to apply the proposed method for numerical simulation of thermal processes in REM designs, verification based on the results of a full-scale experiment, as well as the creation of methods for the justified application of existing and the development of new mathematical algorithms for optimization procedures.

DEVELOPMENT OF AN APPLICATION FOR THE THERMAL PROCESSING OF OIL SLIME IN THE INDUSTRIAL OIL AND GAS SECTOR

The production activities of oil refineries and oil and gas-producing enterprises inevitably have an anthropogenic impact on the environment, so environmental issues and the rational use of natural resources are important. The most dangerous pollutants of all components in the natural environment are oil waste, and one of the most effective methods of processing is heat treatment. The task was set to neutralize oil waste by thermal processing of oil slime to an environmentally safe level. The studies are carried out by methods of mathematical and numerical simulation of thermal processing, the results of which describe changes in temperature and mass of the stream over time. Extensive calculations with varying current operating and other parameters allow us to optimize the flow of heat and mass transfer during the thermal processing of oil slime. Numerical modeling is implemented using the method of alternating directions in an implicit iterative scheme until a convergence condition is met. The purpose of this work is to create an application for solving research and practical problems of oil waste processing. The application used allows the solution of the problems of oil slime processing. With the help of color-animated illustrations and a graphical interface, it supports the visualization of the results obtained, and provides the possibility of interactive interaction with the user, while providing instant control of the results obtained for timely decision-making to prevent environmental pollution in the industrial oil gas sector.

Numerical simulation of thermal sterilization heating process of canned fruits with different shapes based on UDM and RDM

Abstract The random distribution model (RDM) and uniform distribution model (UDM) were used to simulate the thermal sterilization of canned fruit. The RDM was established with the radiation function, and the stability of RDM results was analyzed by simulating temperature change during thermal sterilization and determining the sterilization parameter F value of the slowest heating zone (SHZ). The performance of the distribution models in simulating thermal sterilization heating process of canned fruit with different shapes was studied using the UDM and RDM of canned yellow peach (hemispherical shell), pear (sphere), and coconut (cube). Simulation results were compared with experimental results. The flow field and temperature field distributions were used in analyzing the influence of fruits shape on the accuracy of the models. The simulation results of different RDMs were consistent with the temperature change and F value, indicating that the RDMs had stable simulation results. When the contact between two types of fruit was a point, the UDM can be used in the numerical simulation of thermal sterilization. When the contact was a non-point, the RDM was more accurate in simulating thermal sterilization. This study provides constructive suggestions for the simulation of thermal sterilization of canned fruit with different shapes.

INVESTIGATION OF INFLUENCE OF FACTORS ON FIRE RESISTANCE OF PARTITIONS MADE OF SANDWICH PANELS

The authors describe the results of studies of thermal processes in partitions made of sandwich panels under one-sided influence of fire. Analysis of the thermal state of multilayer partitions with mineral wool plates and development of recommendations for the design of buildings from such structures is possible using the simulation of thermal processes that occur during fire exposure to the studied samples. There is a certain number of models of the thermal state of multilayer partitions with mineral wool plates of different levels of complexity and purpose. However, in these models there are parameters that are individual for each partition and are known with insufficient accuracy. The authors provided an improved mathematical model of heat conduction in partitions, the difference of which is the application of heat transfer coefficients from the unheated surface of the partition in boundary conditions. A comparison of the fire resistance limits for a partition made of a sandwich panel indicates a strong influence of the accuracy of setting the heat transfer coefficient on the dependence of the thickness of the partition on the fire resistance limit. The accuracy of the task of the heat transfer coefficient on the dependence of the thickness of the partition on the fire resistance limit was scientifically substantiated, which showed a strong influence of the boundary condition describing the processes of heat transfer on the surface of the partition, which is not heated, on the accuracy of determining the limits of fire resistance of the structure under study. The influence of the accuracy of the assignment of the coefficient of heat transfer from the object to the environment on the fire resistance of the investigated building structures, which during the test are subject to both natural (mobility) of air and forced blowing, as, for example, during tests of air ducts with fire protection, must be taken into account convectively radiation heat exchange, which will allow to obtain the most accurate result regarding the determination of their fire resistance characteristics. Keywords: fire-resistance, methodological support, parameters, modeling.

Thermal process simulation and multi-variable study/optimization of a novel geothermal-driven multi-generation process using bi-evaporator with zeotropic mixture

Bi-evaporator technology is a robust tool, operating in two levels of coolant production for normal cooling and freezing purposes. The current study is motivated to assess the feasibility of integrating a bi-evaporator technology and a single-flash geothermal power plant. The main novelty of this paper is to design a novel combined cooling and power (CCP) production cycle relying on an organic Rankin cycle and a modified bi-evaporator refrigeration cycle. In addition, the use of a zeotropic mixture (Pentane/Isobutane) fed to the CCP is another difference between the current research and the available literature review. In addition to the power and cooling, the entire system is boosted by the use of a multi-generation process, producing heating via a heating production unit and hydrogen (H2) via a low-temperature electrolyzer. The proposed system was analyzed from the energy, exergy, specific exergy costing, and net present value points of view. Therefore, a coherent single- and dual-sensitivity study is done, and the variability of the main performance metrics is viewed against the decision parameters. In addition, owing to the incompatible trend of the newly devised plant's chief performance metrics, an advanced triple-objective optimization through a NSGA-II method is regraded from the standpoints of thermodynamics and economics. The objective functions include the coefficient of performance, exergy efficiency, and sum unit cost of products, and the optimum solution reveals their values of 33.56%, 63.2%, and 6.0 $/GJ, respectively.

Thermodynamic Simulation of Thermal Processes Involving Actinides (U, Am, Pu) during Heating of Radioactive Graphite in a Mixture of Water Vapor and Oxygen

Thermodynamic Simulation of Thermal Processes Involving Actinides (U, Am, Pu) during Heating of Radioactive Graphite in a Mixture of Water Vapor and Oxygen

Simulation of thermal and erosion processes in a multichannel hollow cathode

Simulation of thermal and erosion processes in a multichannel hollow cathode