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This investigation proposes a systematic framework based on the Fault Tree analysis, for the energy and exergy optimization of a paper machine. In the first step, energy and exergy analysis was performed on the dryer section and its related steam and condensate system, to assess the existing performance of paper machine. In the next step, checklists were developed for the identification of key safety and operational issues related to the steam and condensate system. Then, a fault tree analysis was applied to make out and resolve the root causes. Corrective actions were taken in order to rectify various problems. As a result, energy and exergy efficiencies of the system increased by 22% and 14%, respectively. Moreover, an improvement in steam and condensate recovery system was observed. [ABSTRACT FROM AUTHOR]

The current discussion is presented to increase the awareness among the readers of the journal Thermal Science. Comments are presented in particular on the paper by Hayat et al. [1] where the authors investigated effect of non-linear radiative flow of third grade fluid and temperature dependent heat source with chemical aspects. The current discussion concerns some questionable results included in the aforementioned paper. [ABSTRACT FROM AUTHOR]

In this paper, the thermodynamic and economic efficiency of three different heat supply processes are compared, based on exergy flows and costs of heat. A gas turbine process with a heat recovery boiler, a gas and steam turbine combined cycle process and a high temperature heat pump system recovering waste heat are analysed. The aim is to provide heat as 4 bar(abs) saturated steam. The economic analysis bases on the comparison of the consumption-related costs of heat, the capital-related costs of heat, and the operation-related costs of heat. The results show that the heat pump system has higher exergetic efficiency than the gas turbine or the gas turbine combined cycle process. For the consumption related costs, the economic calculation shows that the operation of a heat pump, working with a coefficient of performance of four and for a natural gas price of 25 €/MWh, is the cheapest way of heat production as long as the electricity price is lower than 45 €/MWh. For the period from January 2013 until June 2016 the total costs of heat, based on real gas and electricity prices from the European Energy Exchange, are calculated and analysed. The results show that the share of heat provided by the heat pump system varies between 45% and 76%. Especially in 2013 and 2014, the economic conditions for operating heat pumps were very good. Since October 2015 the natural gas prices have seen a decrease which favours industrial heat supply with combined heat and power systems. [ABSTRACT FROM AUTHOR]

This paper considers a temperature-dependent thermal conductivity with memory property in a fractal space. The two-scale fractal derivative is adopted to model the temperature field in the spatial dimensions, and Caputo fractional derivative is used to describe its memory property. The variational iteration method is employed to solve the mixed model with great success. This paper offers a new window for studying intractable problems arising in porous media or unsmooth boundaries. [ABSTRACT FROM AUTHOR]

This paper introduces a novel design for a solar photovoltaic/thermal (PV/T) air collector that utilizes staggered fins. The collector features double-layer flow channels in the same direction, with the upper channel equipped with transparent wave plates, and the lower channel fitted with staggered fins. The paper includes a calculation scheme for wave plate heat balance. The numerical model of the collector is established and verified by experimental results. A numerical model is used to analyze the height combination of the upper and lower runner and the fin arrangement of the lower runner. The results indicate that, under the given environmental parameters, as the PV panel moves down, the overall air heat transfer capacity decreases. When the height combination of the upper/lower runner is 23 mm/105 mm, the maximum value is 53.741%. With the increase of fin spacing, the heat transfer capacity of the lower runner decreases. With the increase of the number of fin rows, the heat transfer capacity of the lower runner increases. When the equivalent diameter of the rectangular channel and the number of fin rows were 70 mm and 3 rows, respectively, the maximum solar energy comprehensive utilization efficiency was 56.261%. [ABSTRACT FROM AUTHOR]

This paper was written to demonstrate the value of using nanofluids for cooling high power transformers while also providing current techniques for business and academia. A numerical analysis of the improvement caused by the cooling of a high voltage transformer using nanofluids has been done. A tank with a temperature source inside and a charge of mineral oil-barium titanate nanoparticles is used to study natural-convection. This study investigates the effects of variables on the thermal efficiency of the tank, including the thermal Rayleigh number and volume fraction. The results show that quenching varies with low and high Rayleigh thermal numbers and depends on the volume percentage of used nanoparticles. The effects were illustrated in thermal transfer rate representations as functions of the thermal Rayleigh number (Rat = 103 and 106) and the solid volume particle from the nanoparticles (0% = f < 10%). The findings showed that improving the solid volume particle of the nanoparticles by 10% causes the fluid being utilized to become more effectively conductive, which improves the rate of heat transfer by roughly 10% when compared to the case of the base fluid. [ABSTRACT FROM AUTHOR]

Helium (He) tracer method is one of the common methods used to detect tube bundle leakage in the condenser. To improve the detection accuracy, sulfur hexafluoride (SF6) is considered a tracer gas instead of He. This paper combines the N-S equation, porous medium model, flow diffusion model and steam heat transfer model to develop the numerical model of tube bundle leakage in the condenser. The simulation results show that the transport of leaked gases (He and SF6) consists of flow and diffusion patterns. The existence of the diffusion process is confirmed further through theoretical analysis. The two gases have the same transport behavior in the pure flow process. When it involves the diffusion process, the flow rate of He is 6.67 times that of SF6. In other words, the time required for He to reach the same concentration difference is 1/6.67 times that of SF6. In addition, the influence of leakage intensity and gas species on the transport is analyzed. The study results provide a theoretical basis for SF6 to replace He as a tracer gas to detect tube bundle leakage. [ABSTRACT FROM AUTHOR]

In this paper the 2-D steady-state heat transfer geometric inverse problem is solved using the finite element method, conjugate gradient method, and firefly algorithm. Based on the finite element method for solving the forward heat transfer model, and based on continuous iterative optimisation of the conjugate gradient method, the accuracy of the error function of the measured and estimated values is kept within a certain range, so that the geometry of the object under test can be calculated in an inverse way. In the study of the forward problem, the temperature field distribution is solved using circular pipes as the research objects, and the feasibility of applying the finite element method to heat transfer problems is verified. The inverse problem takes the circular tube as the object and considers two different corrosion defects on the inner wall of the circular tube. Simultaneously, the firefly algorithm is introduced based on the conjugate gradient method to stochastically optimize the temperature data and suppress the fluctuation of the inversion result. Numerical experiment results indicate that the method in this paper can perform more accurate geometric shape recognition when there is a certain temperature measurement error or the temperature measurement information is relatively complete. [ABSTRACT FROM AUTHOR]

In order to study the influence of the louver angle on the heat transfer and flow resistance characteristics of a parallel flow heat exchanger, this paper establishes five calculation models including a uniform angle model and four variable angle models for comparing and analyzing the temperature, velocity, and pressure fields, and evaluates their comprehensive performance. The results show that the suitable choice of the v louver angle can lead to an optimal heat transfer effect and a best comprehensive performance. [ABSTRACT FROM AUTHOR]

This paper studies a self-designed high temperature fireball quasi-static simulation device to understand the temperature distribution of each substance inside the fireball under the multi-pipe injection technology. The changes in the physical field of the high temperature fireball are obtained through numerical simulation. The simulation model in this paper adopts the turbulent k-ε model, and simulates the material transfer process according to Fick's law. The commercial software COMSOL multiphysics is used to give and analyze the local characteristics of fluid-flow and heat transfer. The simulation device formed a high temperature fireball under the interaction of the three-way jet fire. The experimental data verified the accuracy of the simulation results, and the experimental results were in good agreement with the simulation results. This method of analyzing the actual temperature field through simulation can be used to provide a powerful verification scheme for the detection of complex multi-temperature fields in the future. [ABSTRACT FROM AUTHOR]

In this paper, a new split iterative compact difference scheme for a class of system is constructed. Then, the conservation properties of the scheme are discussed, and the convergence of the split iterative difference scheme is analyzed by using the discrete energy method on the basis of the prior estimation. Finally, numerical experiments verify these properties of the new scheme. In addition, the numerical results also show the influence of fractional derivative on the variation of the transport equation. [ABSTRACT FROM AUTHOR]

At present, most numerical methods consider the tube walls as the same constant temperature in the simulations of the heat exchanger, and only the external fluid outside the tubes is considered. To investigate the heat transfer performance of the heat exchanger in the real running state, a conjugate heat transfer simulation is performed for a heat exchanger equipped with cross-combined ellipsoidal dimple tubes in this paper. The k-e standard turbulence model is selected to simulate the heating process of tube bank. The distributions of the temperature field and flow field are analyzed carefully. The results indicate that the temperature distribution and the heat flux on the tube wall are uneven, which is different from the case regarding the wall boundaries as a constant temperature. The heat transfer performance of the dimpled tube is higher than that of the smooth tube in the heat exchanger, and the heat transfer performance for aligned arrangement is better than that for staggered arrangement. In addition, the influences of geometric and flowing parameters on heat transfer are discussed. [ABSTRACT FROM AUTHOR]

Gathering and transportation pipelines often appear shutdown condition due to damage, leakage, and other reasons. The reasonable maintenance time should be controlled by closely combined with the change law of the oil-water temperature in the pipeline. This paper established a multi-field coupling 3-D heat transfer mathematical model of the oil-water pipeline environment based on the two-phase shutdown pipeline as the research object. According to the changing law of the oilwater temperature field and flow field under a typical pipe diameter, the evolution behavior of the gelation layer in the pipe and the transformation process of heat transfer mode were analyzed, and the heat transfer characteristics between oilwater phase and its interface in the pipe were defined. With the liquid phase ratio of the oil phase changing the rule, reasonable maintenance time suggestions were given for gathering and transporting pipelines with different water content. [ABSTRACT FROM AUTHOR]

The combustion of fuel under intense volumetric forces has the potential to enhance the velocity of flame propagation. To investigate the influence of volumetric forces on the combustion process and the characteristics of flame propagation within fuel, this research paper conducted a numerical analysis of a 2-D rotating pipe subjected to varying volumetric forces. The findings reveal that, within a specific range, an augmentation in volumetric forces progressively elevates both the global and localized speeds of flame propagation. The primary rationale behind the heightened flame propagation speed under intense volumetric forces lies in the fact that the increase in such forces facilitates an enlargement of the interface area between the burned and unburned gases. This, in turn, fortifies the transfer of heat and the chemical reaction rate between the two, effectively shortening the duration of combustion and augmenting the speed of flame propagation. At exceedingly low volumetric forces, the pressure wave generated by combustion in the pipe exerts a certain influence on the speed of flame propagation and the progression of the flame. [ABSTRACT FROM AUTHOR]

It is a new practical method to apply external magnetic field in magnetic working fluid to enhance heat transfer. In this paper, the swirl flow and heat transfer characteristics of ferrofluid in elliptical tubes under thermal-magnetic-flow fields coupling have been studied by using the finite volume method. The flow structure and secondary vortices evolution process of magnetic nanofluid in elliptical ducts under the action of the magnetic fields have been obtained. The effects of magnetic induction intensity and the ratio of major axis to minor axis of elliptical pipe on the flow and heat transfer performances have been main investigated. The results show that there is obvious secondary flow (with four vortices or eight vortices) on the cross-section and the swirling flow is gradually formed due to the coupling of thermal-magnetic-velocity fields. With the increase of the ratio of major axis to minor axis, the heat transfer enhancement effect with the application of external magnetic field is weakened. The comprehensive performance of flow and heat transfer are better at lower Reynolds number and higher magnetic induction intensity. [ABSTRACT FROM AUTHOR]

Plate heat exchangers are realized by means of a heat transfer mechanism, in which heat is naturally transferred from the hot substance to the object with a lower temperature according to the laws of thermodynamics. Two liquids of different temperatures flow on the wall, heat transfer on the wall and convection of the liquid on the wall, thus promoting heat transfer between the two liquids. Under the same flow rate and power consumption conditions, its heat transfer coefficient is three times that of shell and tube heat exchangers, which is a key and efficient new equipment for effectively using effective resources and saving and developing new energy. However the heat supply plate heat exchanger has a tiny circulation surface and is easily obstructed. Regular maintenance and cleaning, troubleshooting, and plate replacement all necessitate frequent heat exchanger disassembly and installation. The requirements and challenges in dismantling and assembling the heat exchanger are very high, and manual disassembly is wasteful, making consistent force difficult to achieve. The current methods of disassembly and assembly are inefficient and incorrect. The intelligent mechanization of disassembly and assembly equipment is realized in this paper by driving, clamping, automatic control, distance measurement, sensing, and other systems. The problems of uneven force, low efficiency, and precision in plate heat exchanger disassembly and assembly are solved. Our power disassembly equipment for high efficiency heat transfer plate heat exchangers not only enhances disassembly efficiency and precision, but it also ensures the safe operation of the plate heat exchanger heating system, and the heat transfer efficiency and heat exchange efficiency are improved. Furthermore, it has a wide range of applications in the petroleum, chemical, and other industries. [ABSTRACT FROM AUTHOR]

The paper contains a response to the comment by Popovich and Mincheva, focusing on the different meanings of the analysis according to the First and the Second law of thermodynamics and their complementary and never alternative nature. [ABSTRACT FROM AUTHOR]

Droplet positive collision is a complex process involving heat transfer in gas-liquid-solid three-phase flow and droplet collide dynamics. In order to study the kinetic behavior of droplets under positive collision in low velocity (v < 2 m/s), this paper focuses on the spreading, vibration, and fracture characteristics of double droplets by numerical simulation. First, the accuracy of the model is verified by experimental comparison. The effects of droplet diameters, collision velocities and wall contact angles on the spreading process are analyzed, and the spreading factor curves are plotted. Then, the droplet rebound vibration after collision fusion is equated to a single-degree-of-freedom damped vibration system, and the peak vibration height variation curve of the fused droplet is obtained by non-linear fitting. Considering the droplet phase change, the influence law of different conditions on the vibration damping factor and vibration time of the fused droplet is studied. Finally, it is found that rebound fracture and spreading fracture occur after the fusion of double droplets under positive collision, and the critical values of collide velocity required for the occurrence of the aforementioned phenomenon are found. To provide a reliable theoretical basis for the study of heat and mass transfer processes after multiple droplets collide the wall. [ABSTRACT FROM AUTHOR]

This paper is devoted to the analysis of an unsteady 2-D MHD dynamic and thermal boundary-layer over a horizontal cylinder in mixed convection, in the presence of suction/injection, heat source/sink, and heat radiation fluid electrical conductivity is constant. The system of MHD equations of dynamic and temperature boundary-layer, which describe complex non-auto model problems, has been solved by a new approach. New variables and sets of parameters were introduced and transformed equations were obtained, in which the influence of the magnitude Z was explicitly retained. In order to close the system of equations, to the equations of the boundary-layers momentum equation was added. The solution of the obtained system of non-linear differential equations was performed numerically using the finite difference method, with the simultaneous application of the iteration method. By replacing the derivatives in the system of equations with the corresponding relations of finite differences, a system of linear derivative algebraic equations is obtained, which is solved by the three-diagonal method. As a concrete example of the introduced method, the effects of heat transfer in the MHD boundary-layers were considered, in the case of mixed convention, over a horizontal circular cylinder. The boundary conditions for temperature are defined by linear functions of longitudinal co-ordinates and time. Numerical results for different Eckart, Schmidt, and expanded Prandtl numbers and values: magnetic, dynamic, thermal parameters, temperature, and buoyancy parameters were obtained and presented. The obtained results were analyzed through the diagrams of changes in velocity and temperature and the diagrams of integral and differential characteristics of boundary-layers and the corresponding conclusions were given. [ABSTRACT FROM AUTHOR]

Magnetohydrodynamic fluid-flows attract a lot of attention in the extrusion of polymers, in the theory of nanofluids, as well as in the consideration of biological fluids. The considered problem in the paper is the flow and heat transfer of nanoand micro-polar fluid in inclined channel. Fluid-flow is steady, while nano- and micro-polar fluids are incompressible, immiscible, and electrically conductive. The upper and lower channel plates are electrically insulated and maintained at constant and different temperatures. External applied magnetic field is perpendicular to the fluid-flow and considered problem is in induction-less approximation. The equations of the considered problem are reduced to ODE, which are analytically solved in closed form. The influence of characteristics parameters of nano- and micro-polar fluids on velocity, micro-rotation and temperature fields are graphically shown and discussed. The general conclusions given through the analysis of graphs can be used for better understanding of the flow and heat transfer of nano- and micro-polar fluid, which have a great practical application. Fluids with nanoparticles innovated the modern era, due to their comprehensive applications in nanotechnology and manufacturing processes, while the theory of micro-polar fluids explains the flow of biological fluids and various types of liquid metals and crystals. [ABSTRACT FROM AUTHOR]

This paper discusses the fully developed electromagnetic hydrodynamic flow and heat transfer of a Casson nanofluid Fe3O4-blood in a porous medium. The flow takes place in a horizontal channel with walls at different temperatures. The channel is influenced by an externally applied magnetic field that is perpendicular to the walls of the channel and an externally applied electric field that is perpendicular to the longitudinal vertical plane of the channel. Both of these fields are homogeneous. The induced magnetic field is considered weak and can be neglected. The described problem is represented by differential equations which are analytically solved after the transformation into a dimensionless form. The obtained velocity and temperature distributions of the Casson fluid Fe3O4- blood are graphically represented and the influences of the Hartmann number, the Brinkman number, the power factor, the porosity factor, and the volume fraction of nanoparticles are examined. The Nusselt number and dimensionless friction voltages are given in a table. [ABSTRACT FROM AUTHOR]

In order to solve the problem of severe stator winding heating due to the single cooling structure of a permanent magnet synchronous motor for electric vehicles, and to further improve the heat transfer capability of the permanent magnet synchronous motor, a new water-cooled structure is proposed in which cooling pipes are placed at the stator yoke to increase the heat transfer area. In order to evaluate the heat transfer effect of this new water-cooled structure, this paper takes a 50 kW permanent magnet synchronous motor for electric vehicles as the research object. By establishing a 3-D full-domain fluid-solid coupled heat transfer model, setting boundary conditions and reasonable assumptions, the full-domain fluid-heat coupled field of the permanent magnet synchronous motors is calculated numerically, and the fluid-flow characteristics and heat transfer variation laws of the new water-cooled structure are analyzed. The results show that compared with the original cooling structure, the maximum temperature drop of stator winding and permanent magnet can reach 5.23% and 11.17%, respectively. The results obtained can provide a reference for future research on the thermal performance and water-cooled structure optimization of permanent magnet synchronous motor for electric vehicles. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue on topics including thermodynamic model; Low Gibbs Energy; and Lytic Cycle Hijack Cell Metabolism.

To demonstrate the rationalization of multi-longitudinal swirls in heat exchanger tubes, this paper investigates the thermohydraulic performance of heat exchanger tube with rectangular vortex generator using numerical simulation. Comparative analyses of rectangular vortex generators and their different slotted structures are conducted, along with the investigation of the effect of the longitudinal pitch (P = 0.1 m, 0.2 m and 0.3 m) of the rectangular vortex generators on the thermohydraulic performance. The research reveals that the multi-longitudinal swirls induced by the vortex generator inside the tube accelerate the exchange of cold and hot fluids, improve the field synergies of velocity vectors and temperature gradients, and enhance the heat transfer efficiency of the heat exchanger tube. The slotted structure reduces the flow resistance and lowers the degree of disturbance to the fluid, which reduces the strength of the multi-longitudinal swirls, thus weakening the overall performance of the heat exchanger. The strength of the multi-longitudinal swirls has a direct influence on the overall performance of the heat exchanger tube. With the increase of P, the performance evaluation criteria (PEC) of the heat exchanger tubes decreases, and the maximum PEC = 1.44 is obtained for P = 100 mm at the studied Reynolds number range. [ABSTRACT FROM AUTHOR]

Direct air-cooled condensers in power plants rely on heat transfer with the atmospheric environment to discharge thermal energy. The heat transfer process becomes complicated in practical operations when ambient wind is involved. To examine the impact of wind on the heat transfer performance of direct air-cooled condensers, this paper took into consideration three different wind directions, namely, headwind, crosswind and tailwind, as well as four different speeds (3 m/s, 6 m/s, 9 m/s, and 12 m/s), and numerically investigated their influences on the thermal performance of a 600 MW direct air-cooled power unit. The variation in ventilation rates and inlet air temperatures among the cells under the influence of ambient winds are also studied. Simulation results indicated that ambient winds induced thermal air re-circulation and air backflow phenomena in the air-cooled island. The cells located on the windward side were significantly affected in all three wind direction conditions. The ventilation rates and inlet air temperatures among the cells were not uniform, showing an overall increasing trend. In particular, negative pressure zones were generated under tailwind conditions, severely impacting air-flow rates at the fan inlet, and inlet air temperatures of cells. These phenomena became more pronounced with increasing wind speeds. [ABSTRACT FROM AUTHOR]

The purpose of this paper to explain the role and importance of fractional derivatives for mass and heat transfer in Casson nanofluids including clay nanoparticles. These particles can be found in water, kerosene, and engine oil. The physical flow phenomena are illustrated using PDE and thermophysical nanoparticle properties, and this paper addresses the Casson fractional fluid along with chemical reaction and heat generation. The heat and mass fluxes are generalized using the constant proportional Caputo fractional derivative. The present flow model are solved semi-analytically using the Laplace transform. We generated several graphs to understand how various flow factors affect velocity. The acquired results reveal that fractional parameters have dual behavior in velocity profiles. Velocity and temperature are also compared to previous studies. Compared to the other fractional derivatives results, field variables and proposed hybrid fractional derivatives showed a more decaying trend. Furthermore, significant results of clay nanoparticles with various base fluids have been obtained. [ABSTRACT FROM AUTHOR]

Particulate matter has important influences on premature human mortality. Diesel particulate filter is one of the most effective means to reduce particulate matter in exhaust gas. In order to study the 3-D flow characteristics of diesel particulate filter porous structure, lattice Boltzmann method is used to study the flow and heat transfer characteristics of different structures. In some software, the spherical structure is used as diesel particulate filter porous structure. In paper, the spherical structure, the quartet structure generation set structure, and the computer tomography technique structure are constructed. The computer tomography technique structure is constructed by the serial sections of diesel particulate filter porous structure. The flow and heat transfer characteristics in different structures were simulated by lattice Boltzmann method. The 3-D computer tomography technique structure is constructed by superposing the serial section data of diesel particulate filter. The results show that the pressure gradient and temperature gradient of structures are greatly affected by the structure. The pressure gradient and temperature gradient of the spherical structure is the lowest. The spherical structure and the quartet structure generation set structure are different from the porous structure of diesel particulate filter in pressure gradient and temperature gradient. By comparing different structures, it can be seen that although the pressure gradients of the computer tomography technique structure and the quartet structure generation set structure are similar, the temperature gradient of the two structures are more different. [ABSTRACT FROM AUTHOR]

Commentaries are presented on Ye et al. [1]'s paper, where the authors investigated the performance of heat transfer in evaporator under the case that the parameters of the heat source and temperature of pinch point were identified. They utilized the graphical method of temperature-heat (T-Q) diagram analysis. Also, they utilized the entransy principle in their analysis. Commentaries show the reality that the graphical method of T-Q diagram analysis belongs to Professor Adrian Bejan, who first proposed it in 1977. In addition, many instances in the literature are given to indicate disputes for the entransy principle by oppositionists of "entransy" from various countries. [ABSTRACT FROM AUTHOR]

To improve the efficiency of the heat exchanger tube, one smooth tube and four doubly enhanced tubes (EX1, EX2, EX3 and EX4) have been investigated for the pool boiling heat transfer experiments in this paper. The indicate that the pool boiling heat transfer coefficient of the doubly enhanced tubes increased visibly with the augmentation of heat flux through the bubble behavior. Heat transfer reinforcement effect of the doubly enhanced tubes are significantly better than that of the smooth tube. Additionally, pool boiling heat transfer coefficient can be further enhanced by raising the saturate temperature. Entropy generation minimization analysis demonstrates that the heat transfer characteristics of like T-shaped tubes (EX1 and EX2) are superior to that of low fin tubes (EX3 and EX4). Particularly, tube EX1 exhibits higher pool boiling heat transfer efficiency. It is observed that a reasonable fin pitch is more advantageous for improving heat transfer characteristics. The utilization of entropy generation minimization analysis provides theoretical support for the design and optimization of doubly enhanced tubes. [ABSTRACT FROM AUTHOR]

In order to provide a more comprehensive depiction of the actual heat transfer process in energy piles, this research paper presents an approximate solution for a finite line heat source model operating under variable heat flow conditions. This solution is established by integrating the finite line heat source model and the superposition principle. Furthermore, the W-tube heat exchanger is divided into many segments, and a segmented superposition approach is used based on the thermal response. Consequently, a heat transfer model for a single-pile heat source is formulated, taking into consideration the heat exchange between the circulating water and the energy pile. Notably, the soil temperature predicted by this proposed model closely aligns with the results obtained from the FLUENT numerical model, thereby substantiating the accuracy of the proposed approach. Simultaneously, the heat transfer model is employed to analyze variations in temperature and heat flux density within the heat exchanger and to investigate the influence of parameters such as mass-flow rate, pile-soil heat transfer coefficient, pile-soil density, and pile-soil specific heat capacity on the heat transfer characteristics of energy piles. This model enables the determination of time-varying heat flux and precise outlet temperature, thereby facilitating a rapid assessment of the heat transfer efficiency of energy piles. [ABSTRACT FROM AUTHOR]

In this paper, the effect of different forms of electric heating wire forms on the anti-icing performance of the refrigerated container was studied based on numerical simulation. The heat transfer and the thermal conductivity of the refrigerated container door wall, and the uniformity of air-flow distribution in the refrigerated container are analyzed. The heating wire form 2 has the best anti-icing performance and meets the anti-icing requirement when the thermal conductivity is from 0.005-0.01 W/mK. The electric heating wires nearest to the inner wall surface is the optimal anti-icing solution. The spare electric heating wires placement can be determined according to the thickness of the refrigerated container door. The specific lay-out of electric heating wires in the future can be further optimized in combination with carbon emissions. [ABSTRACT FROM AUTHOR]

The objective of this paper is to evaluate the capability of an ANN to classify the thermal conductivity of water-glycol mixture in various concentrations. Massive training/validation/test temperature data were created by using a COMSOL model for geometry including a micropipette thermal sensor in an infinite media (i.e., water-glycol mixture) where a 500 µs laser pulse is irradiated at the tip. The randomly generated temporal profile of the temperature dataset was then fed into a trained ANN to classify the thermal conductivity of the mixtures, whose value would be used to distinguish the glycol concentration at a sensitivity of 0.2% concentration with an accuracy of 96.5%. Training of the ANN yielded an overall classification accuracy of 99.99% after 108 epochs. [ABSTRACT FROM AUTHOR]

In this paper, the convective-radiative fins of rectangular profile with temperature-dependent thermal conductivity are considered. By studying the conventional heat transfer equation, its modified fractal form, which can describe the problem in the porous medium, is presented based on He's fractal derivative for the first time. The fractal two-scale transform method together with the Taylor series are applied to deal with fractal model, and an analytical approximate solution is obtained. The impact of the different fractal orders on the thermal behavior of the fins is also elaborated in detail. In addition, a comparison between our solution and the existing one is given to prove the correctness of the proposed method, which shows that the proposed method is easy but effective, and are expected to shed a bright light on practical applications of fractal calculus. [ABSTRACT FROM AUTHOR]

This paper is to investigate microscale flow and transfer between the rotor and the flank for rotary engine. The rotor and flank are simplified to two disks in order to study flow field and temperature field conveniently. The paper takes analysis of steady laminar flow and heat transfer between two disks separated by a gas-filled gap due to machining tolerance. A 3-D multi-physical coupling model is used, involving velocity slip, temperature jump, rarefaction, and dissipation. A solution based on commercial code COMSOL is derived and the results are used to illustrate the effects to velocity field, temperature distribution, disks' torque, and Nusselt number based on the governing parameters. The paper also investigates the effects of different modified Knudsen number on flow field and temperature field. [ABSTRACT FROM AUTHOR]

The explosion intensity and the low explosion limit of the coal dust explosion are affected by the calorific value and the heat transfer rate of the coal dust, which are closely related to the coal quality index. This paper studies experimentally the low explosive limit of the coal dust with different coal quality indexes. Based on the principal component analysis, the main factors affecting the low explosive limit are obtained by extracting the principal components from the coal quality indexes. Through comparative analysis, a regression model is proposed to predict the low explosive limit for practical applications. [ABSTRACT FROM AUTHOR]

Through silicon via technology is a promising and preferred way to realize the reliable interconnection for 3-D integrated circuit (3-D IC), which can transfer heat from multiple dies to the heat sink in vertical direction. In this paper, a new general model of the through-silicon via (TSV) is proposed to investigate the thermal performance of the 3-D IC. The heat transfer characteristics of conical-annular TSV are studied for the first time. The impacts of different sidewall inclination angles and insulating layer thicknesses of TSV on the heat dissipation of 3-D IC were compared and analyzed in detail. As expected, our proposed model is in good agreement with the results of the existing models, which shows that the proposed model considering the lateral heat transfer and TSV structures can predict the distribution of temperature more efficiently and accurately. Furthermore, it is found that conical-annular TSV has more excellent heat dissipation performance. [ABSTRACT FROM AUTHOR]

In order to solve the problems of thermal fatigue, high temperature gasification and low temperature solidification of the heat receiver, a numerical calculation model for the heat transfer function of the tower type solar thermal power generation high temperature receiver is proposed. A perfect analysis method is used for the simulation, and a thermal simulation program for predicting the heat gain of the solar thermal energy tower is compiled. In this paper, considering the various field connection characteristics, numerical value and distribution of convective heat transfer coefficient of the heat absorption medium, the temperature of the outer wall of the heat pipe absorption, and the thermal image conversion work in a non-uniform heat flow boundary area of a model of heat receiver was studied. The experiments show that when the flow rate of molten salt in the tube increases from 1 m/s to 2 m/s, the heat collection efficiency of the heat collection increases rapidly, while the flow time is more 3 m/s, the heat collection efficiency increases more gradually. The efficiency of heat absorption of the heat receiver is in the middle of the heat receiver, which can achieve 88 of the thermal image conversion. In the same large enough value, the heat collected at the inlet and outlet of the heat sink is about 82. It is clear that the numerical simulation provides a reliable basis for the design engineering, and provide guidance for the design of a full control model of tower solar photovoltaic power generation. [ABSTRACT FROM AUTHOR]

The motive of this study is to investigate the spinning fluid-flow due to revolving disk for the magnetic unsteady Brownian motion of viscous nanofluid. Here the disk is assumed to have an inverse linear angular velocity. In this paper mass transfer is incorporated in the analysis with the existing problem. The array of equation for the unsteady flow firstly converted into dimensionless non-linear equation using appropriate transformation and then the dimensionless system of equation is further solved numerically utilizing MAPLE software. The different emerging parameters mainly magnetic parameter, variable viscosity, Prandtl number, Eckert number, thermophoresis, and Brownian motion parameter has been investigated through graphs and shown in tabular form also. [ABSTRACT FROM AUTHOR]

This paper's main objective is to perform a numerical analysis of the heat and mass transfer that occurs during the mixed convective drying of porous walls containing hybrid nanofluid. The porous wall, used to dry the brick, is positioned in a vertical channel and has three different phases: a solid phase, a hybrid nanofluid phase, and a gas phase. In order to accomplish this, we created a 2-D code using COMSOL Multiphysics to resolve the equations relating mass, momentum, species, and energy. The impact of various parameters, including ambient temperature, initial hybrid nanofluid saturation, and nanoparticle volume percent, on heat and mass transmission was examined after this numerical code's validity. As the volume percentage of nanoparticles rises, it is discovered that the temperature of the porous medium is significantly lowered. The heat and mass transfer of the water-Al2O3-MgO hybrid nanofluid has been discovered to be much less than that of pure water and the water-Al2O3-SiO2. As the ambient temperature rises, it takes less time for the second phase to dry. [ABSTRACT FROM AUTHOR]

In order to investigate the influence mechanism of various corrugated structures on the heat transfer of continuous annular concave-convex corrugated pipes, this paper examines the influence of corrugation height (Ch = 1 mm, 1.5 mm, and 2 mm) and corrugation width (Cw = 1 mm, 1.5 mm, and 2 mm) on the flow pattern, turbulent kinetic energy, Nusselt number, friction coefficient, and performance evaluation factor. Then, the correlation equations for Nusselt number and friction coefficient are established with different corrugated structural parameters. The results show that with the increase of Ch, the vortex number, turbulent kinetic energy, and friction coefficient in the pipe increase while Nusselt number decreases. The maximum perfomance evaluation factor is 0.90 at Ch = 1 mm. However, with the increase of Cw, the vortex number and Nusselt number in the pipe increase, while turbulent kinetic energy and friction coefficient in the pipe do not change much. The maximum performance evaluation factor is 0.87 at Cw = 2 mm. Therefore, for this type of corrugated pipe, one should choose a small Ch and a large Cw. [ABSTRACT FROM AUTHOR]

Heat shock is a feasible means to break rock mass in engineering duo to the large additional thermal stress caused by thermal expansion. This paper established a coupled thermal transfer and rock deformation model based on the energy conservation and the elastic deformation theory of rock. In the model, the failure and damage of rock are judged according to the Drucker-Prager criterion. A finite element method of COMSOL Multiphysics to study the characteristics of temperature, stress distribution and damage zone on a rock surface is proposed. Results show that the failure of rock mass occurs at the cusps of the heater first duo to stress concentration and then grows at both sides of the heater greatly. [ABSTRACT FROM AUTHOR]

As a kind of clean and renewable energy, shallow geothermal energy has the characteristics of wide distribution and huge reserves. The use of pile foundation heat exchange for building heating is a new technology to realize the effective utilization of geothermal energy. Improving the mechanical properties of the pile body material and improving the heat exchange efficiency of the pile foundation concrete will effectively promote the application of concrete in building structures. In this paper, the effect of steel fiber content on the thermal conductivity and mechanical strength of concrete is discussed by carrying out physical and mechanical properties test of concrete material of pile body. It is proposed to incorporate steel fibers into the concrete of the pile body to improve its thermal conductivity, thereby improving its heat transfer efficiency per unit time. At the same time, the role of steel fiber in enhancing heat transfer performance in pile material is analyzed from the microscopic mechanism, which provides theoretical support for the optimization process of concrete ratio of pile foundation in practical engineering. [ABSTRACT FROM AUTHOR]

The heat exchanger can use shallow geothermal energy to provide regional heating and cooling demand in winter and summer. In this paper, a large-scale public building is taken as the example, and the energy system in the building is taken as the research object. Firstly, through the collection of geothermal drilling geographic information and geothermal data, the geothermal reserves and geothermal recoverable resources are evaluated. Secondly, the cooling and heating demand of the building is calculated by using HVAC simulation software. Then, the heat transfer capacity of a single pile is evaluated and the lay-out scheme of the underground heat exchange pile foundation of the building is given. The actual heating effect of the heat exchange pile foundation system is explored, and the heat transfer characteristics of heat exchange pile foundation under different working conditions are compared and analyzed. Finally, reasonable suggestions for the arrangement of heat exchange pile foundation are given. [ABSTRACT FROM AUTHOR]

The paper presents a technical solution for modernization with the aim of increasing the efficiency of the steam boiler of TPP Ugljevik, which implies the reorganization of the combustion system. More efficient operation of the furnace can be achieved by replacing the existing burners, reducing the number of burner levels as well as the organization of tangential combustion. The flame formed in the shape of a tube around the two central combustion vortices provides a larger amount of heat transferred to the combustion furnace, less fouling of its screen walls and thus a lower average temperature of the combustion products at its outlet. As the chosen reorganization affects the increase of the temperature of the superheated steam and the decrease of the temperature of the reheated steam, it has been proposed to reduce the area of the semi-irradiated superheater and increase the area of the second reheater. Taking into consideration that the reorganization of the combustion system may lead to the change of the thermal load of the evaporator located in the furnace, the paper presents the work of the steam boiler operation under new operating conditions. Used calculation system enables reliable prediction of operating characteristics of the steam boiler in new operating conditions of combustion, and its application helps assess the quality of the boiler in terms of how effective, efficient, safe and environmentally friendly its operating mode is. In this way, it is possible to form a comprehensive description of the operating mode of the steam boiler. [ABSTRACT FROM AUTHOR]

In order to study the influence of welding flash on heat transfer performance of steel piston cooling gallery, the pistons with different structures are studied. In this paper, the finite element simulation calculation of the steel piston with the welding flash and the non-flash structure on the same model and the annular cavity section is carried out separately, and the amount of carbon deposited in the top of the steel piston and cooling gallery after 1000 hours test is measured. The comparative analysis finds that the existence of welding flash hinders the heat transfer of cooling gallery, resulting in an increase in the temperature of the inner surface of cooling gallery, which in turn increases the temperature of entire piston head. Carbon deposits in the top surface and cooling gallery of the steel piston, which affects the cooling effect. [ABSTRACT FROM AUTHOR]

High-temperature heat pipes have broad application prospects in terms of thermal protection of hypersonic aircraft and cooling of space nuclear reactors. In this paper, a high-temperature heat pipe heat transfer performance experimental platform is built to study the heat transfer performance of high-temperature heat pipes at different inclination angles. A heat transfer network model of high-temperature heat pipes containing NCG is established to analyze the influence of NCG. The results show that as the inclination angle of the heat pipe increases, the start-up time of the heat pipe does not change. The heat transfer performance is best when the inclination angle is 30°. High-temperature heat pipes containing NCG will reduce the effective length of the high-temperature heat pipe, increase the thermal resistance, and reduce the heat transfer performance. The high-temperature heat pipe analysis model with NCG established in this paper can be used to predict the heat transfer performance of high-temperature heat pipes containing NCG. [ABSTRACT FROM AUTHOR]

In this paper, we attempt to investigate the steady and laminar flow of incompressible water based nanofluid between inclined plates and over an inclined plate. A uniform and external magnetic field is applied in order to control the non-fluid- flow. The Cu-water based nanofluid can be also used for heat transfer enhancement. We can gain additional thermal energy in the fluid by increasing the volume fraction of Cu nanoparticles in the base fluid and improving the thermophysical parameters for the single-phase model. The results also show that adjusting the Prandtl and Eckert numbers causes the velocity profile to change fast. According to our findings, fluid elements may be more intensively accelerated by raising the nanoadditive concentration and enhancing the thermo-physical characteristics of the fluid. [ABSTRACT FROM AUTHOR]

In this paper, the outside cabin heat exchanger based on the porous media approach was established. The effects of altitude, viscous resistance coefficient, inertial resistance coefficient, and core thickness on the naturally captured air volume of the heat exchanger were investigated by numerical simulation. Results showed that the naturally captured air volume of the heat exchanger tends to be larger on both sides and smaller in the middle, and there is a quasi-linear increase proportional to the incoming wind velocity. With the increment of altitude, viscous resistance coefficient, and inertial resistance coefficient, the average naturally captured air volume of the heat exchangers shows a downward trend. The trend would be clear with the increment of the incoming wind velocity, nevertheless, the effect of core thickness is weak. In addition, the design values of the viscous resistance coefficient and the inertial resistance coefficient should be restricted in the order of 106 and below 500, respectively. Based on the weak effect of the naturally captured air volume of the heat exchanger, the thickness of the core can be appropriately increased to ensure the heat transfer area of the heat exchanger. [ABSTRACT FROM AUTHOR]

With the rapid growth of power demand, the conductor ampacity calculation method based on the dynamic thermal rating (DTR) becomes more and more important. Based on the shortcomings of the current DTR models, a new DTR model that does not need to measure the wind speed and the operating state of conductor is proposed, which is called the equivalent heat transfer (EHT) model. However, there are still shortcomings in the accuracy of the EHT model in application. In this paper, the EHT model is improved at first according to the consideration of the effect of air physical parameters and the redetermination of the experimental parameters of the EHT equipment. Then, the operation of EHT equipment is simulated through the established experimental platform. The improved EHT model is verified by the IEEE standard. Finally, the sensitivity analysis of the improved EHT model is carried out. The results show that the improved EHT model is greatly improved on application accuracy compared to the original EHT model. Moreover, the improved EHT model can choose the steady-state temperature at any position on the surface of the aluminum ball to calculate the conductor ampacity, and the relative error does not exceed 6%. The improved EHT model is reliable and can meet the safe operation requirements of the power system in practical engineering applications. [ABSTRACT FROM AUTHOR]

This paper has illustrated a "near wall" combustion model for a spark ignition engine that was included in a two-zone thermodynamic model. The model has calculated cylinder pressure and temperature, composition, as well as heat transfer of fresh and combustion gas. The CO submodel used a simplified chemical equation to calculate the dynamics of CO during the expansion phase. Subsequently, the HC submodel is introduced, and the post-flame oxidation of unburned hydrocarbon was affected by the reaction/diffusion phenomenon. After burning 90% of the fuel, the hydrocarbon reaction dominates at a very late stage of combustion. This modeling method can more directly describe the “near wall” flame reaction and its contribution to the total heat release rate. [ABSTRACT FROM AUTHOR]