Flow Temperature Field Research Articles

Calculation of noise field in main transformer room of indoor substation based on thermal-acoustic coupling

In order to calculate the noise field distribution in the main transformer room of an indoor substation accurately, a thermal-acoustic coupling idea was introduced, and a noise field solving the algorithm based on thermal-acoustic coupling was proposed in view of the noise quality loss caused by the effect of ambient temperature changes. Firstly, the fluid-structure coupling model of the main transformer room is established, and the computational fluid dynamics method is used to calculate the flow field distribution and temperature boundary conditions under the action of the heat source; Then, extracting the rheological equation of the environmental boundary conditions in the flow field calculation, and use the difference function to couple the rheological equation to the sound grid to obtain the sound field coupling model under the condition of variable temperature; Finally, the modified parameter acoustic integral equation under the sound field coupling model is calculated based on the conventional Gauss numerical integration method, and the sound field of the main transformer room considering the effect of variable temperature is obtained. The algorithm has been successfully applied in the analysis of the noise field of Xi'an 110 kV Zhenxing Substation, and the error with the measured value is 2.083%.

Unsteady Mixed Convection Flows in a Rectangular Duct and Dynamical Behaviors of Flow Channel Insert

Buoyancy-assisted upward MHD flows and dynamical behaviors of flow channel insert (FCI) in the dual-coolant lead-lithium (DCLL) blanket are studied numerically. Based on our internally developed and validated solver, the dynamical behaviors of magneto-thermo-fluid-structure coupled multiphysical field are investigated. A large amplitude, low frequency, and quasiperiodic unsteady reverse flow at high Re (31000), high Gr (3.5×1011), and moderate magnetic field (0.7~1.7T) is found in the DCLL blanket. This intricate phenomenon has been discovered for the first time, representing a combination of separate experimental results from Melnikov et al. (2016) and Khanal and Lei (2012). In our study of this large amplitude, low frequency, and quasiperiodic unsteady reverse flows, the importance of the cold helium gas to the instability of fluid flow in the bulk region and the thermal conductivity of the FCI to convection structure and instability are first found and recognized. Additionally, we take into account the effects of the temperature field and flow field on structural deformation and mechanical behavior of FCI, and we have discovered several intriguing phenomena, such as (1) the stability of fluid flow in the bulk region depends on the strength of the heat source, the magnitude of the magnetic field, and thermal conductivity of FCI; (2) the instability and periodicity of the fluid flow are primarily related to the unsteady reverse flow, which rises up and falls down periodically in the bulk region; (3) the physical mechanism of unsteady flow influenced by reverse flow, pressure drop, and Lorentz force has been concluded. It has been discovered that the breakdown of a reverse flow vortex causes a rapid reduction in pressure drop. (4) To avoid this phenomenon in engineering, a phase map of unsteady and steady flows in the DCLL blanket has been created. (5) The quasiperiodic characteristics of solid (flow channel insert) affected by flow are found and analyzed.

Numerical simulation of thermal transfer and flow behavior of Ni60AA formed by laser cladding

The thermal behavior of the cladding layer and the flow behavior of the molten pool significantly affect the geometry, temperature distribution and microstructure of the cladding track, thus affecting the mechanical properties of the cladding. Based on the interaction between the laser and powders, a calculation method of the cross-sectional area of the cladding track is proposed. The droplet energy method and the moving grid method are first combined to establish the surface growth model of the cladding track, to calculate the geometry of the cladding track. Then, the temperature field and flow field of the cladding track are studied. The driving forces of the molten pool flow including shear viscosity, gravity, buoyancy, surface tension at the gas-liquid boundary and pressure between liquids are considered to carry out the dynamics study of the molten pool. According to the force condition of the infinitesimal in the molten pool, the dynamic rules and boundary rules of the molten pool are established, so as to solve the flow field of the molten pool. In addition, the calculated geometry of the cladding track is compared with the experimental result to verify the accuracy of the model, and the microhardness of the cladding track is measured. The results show that the relative error between the simulation and the experiment is less than 6%, and the microhardness of the cladding layer is significantly improved. This work can provide a method for studying the morphology, temperature field, and flow field of laser cladding.

Numerical Simulation and Optimal Control of Composite Nonlinear Mechanical Parts Casting Process

In order to understand the numerical simulation and optimal control of the casting process of Machine element, the author proposed a study based on the numerical simulation and optimal control of the casting process of composite Machine element. Firstly, the author analyzed the structural characteristics of composite Machine element, introduced them in detail, and studied their casting technology in combination with the actual situation. Secondly, the casting process of composite Machine element was simulated by using numerical simulation method, and the temperature field and flow field in the casting filling and solidification process were analyzed. Finally, selecting square cylinders with different wall thicknesses as typical components, the scheme design of traditional single casting process and multi material composite casting process based on dieless casting composite forming technology were carried out. Finite element numerical simulation and experimental research were conducted on the two processes, respectively. The results indicate that: The casting obtained by the multi material composite casting process almost solidifies simultaneously around 200 seconds later, and the graphite morphology around the casting is Type A, with a length of about 100 um, with small differences and uniform distribution; The minimum difference in tensile strength around the casting is about 3.8%, and the maximum increase in tensile strength value is 21%. This research achievement can provide technical reference for high-performance and high-quality casting of complex iron castings. In order to improve the casting quality, the author optimized the casting process of composite Machine element by numerical simulation.

Thermal-Hydraulic Analysis of Pebble Bed High Temperature Gas-Cooled Reactor After Shutdown Based on FLUENT Software

In order to provide a reliable tool for thermal-hydraulic simulation of pebble bed high temperature gas-cooled reactors (HTGRs), a two-dimensional model was developed based on the porous media model and user-defined scalar (UDS) function of FLUENT software. Then, the model was applied to the numerical simulation of the shutdown test of the 10 MW high temperature gas-cooled test reactor (HTR-10) at 9 MW power level, and the temperature distribution and flow field distribution in the reactor were obtained and compared with the results of the experimental data. The reliability of the model in this paper was verified. Based on the model, the effects of the water-cooled panel temperature and the initial core temperature on the thermal-hydraulic characteristics of HTR-10 after shutdown were further explored. The results show that there is a decoupling phenomenon between the residual heat transfer within the core and the heat dissipation of the pressure vessel. The initial core temperature has relatively little effect on the heat dissipation and maximum temperature of the pressure vessel, but it has a significant impact on the thermal characteristics of the core area.

Temperature Field and Flow Field of Molten Pool in SRA EGW

This study investigates the temperature field and flow field of molten pool in seven-wire rotating arc (SRA) electrogas welding (EGW) with the methods of numerical simulations and experiments. The results show that the welding heat source swings back and forth, and the welding heat source starts to heat from the back of the welding workpiece and gradually swings to the front of the welding workpiece with the swing welding arc. The high temperature area of the molten pool and the sidewall penetration are large due to more heat on the molten pool and the sidewall from the unique rotating force, the large arc heating area, and the non-axial droplet transfer. The isotherm distribution of the molten pool is relatively uniform, and the temperature gradient gradually decreases. The simulated welding morphology is generally consistent with the experimental welding morphology with the same welding parameters, which indicates the correctness of the numerical analysis model of the welding temperature field and flow field.

A theoretical model of cross-flow heat transfer for the cooling process in a horizontal moving bed of high-temperature particles

ABSTRACT Besides waste gas and liquid, high-temperature particles are important media of waste heat and their temperature exceeds 1000°C on many occasions. The cross-flow heat transfer is important in this waste heat recovering process, but there are few references reported about the theoretical modeling. Therefore, a theoretical model was developed for the cooling process in a horizontal moving bed of high-temperature particles. The purpose of the study is to estimate the influence of temperature field and flow field on heat transfer and bed resistance in the cross-flow cooling process. Three modes such as conduction, convection and radiation are considered in the model. This model was used to analyze heat transfer in a horizontal moving bed of cement clinker and was verified by comparing some simulative results with the tested and collected data from an actual cement clinker plant in China. The simulative temperature of cement clinker was 200°C as same as that collected in the actual cement clinker plant. In the moving bed, the highest pressure drop occurs at the front top and the strongest heat transfer occurs at the front bottom. In the considered conditions with even distribution of cooling air, the highest pressure drop is 3205.9 Pa/m, the biggest specific heat transfer rate of 1683.1 kW/m3. Thermal radiation plays a minor role in this cooling process with the biggest radiation proportion is only 0.149 at the front top. This mode plays a minor role in this cooling process of the cement clinker, comparing with the thermal convection. With constant flow rate of cooling air, the distribution can regulate the local cooling rate rather than the final temperature of the cement clinker.

Study of Iron and Stony Meteorite Ablation Based on Simulation Experiments in an Arc Heater

To observe meteorite ablation, simulation experiments were conducted on the L5 ordinary chondrite and IAB-MG iron meteorites in an arc-heated facility and three flight conditions were reproduced. To mimic the high heating rates and the significant shear stress that meteorites experience during Earth entry, the samples were machined into 9° spherical cones with a 20 mm nose radius. High-quality video, the surface temperature, a time-resolved spectrum, and infrared video were recorded. The atom species were determined via spectroscopy to analyze the ablation products. Due to the electrode erosion and dissociation of air, the atomic lines of copper, nitrogen, and oxygen were detected in all the tests. Although the copper atom is a pollutant to the flow field, the five copper lines were used to determine the flow-field temperature. The ablation rates and effective heat of ablation of both the samples were measured under different conditions. The results indicate that shear stress is the dominant factor influencing meteorite ablation. Furthermore, the diversity between stony and iron meteorites suggests that the mass loss of stony meteorites depends on the fragmentation of the main body and that of iron meteorites depends on the shearing loss of the molten layer. Then, the fusion crusts were analyzed, the microstructures of the samples were obtained, the crust thicknesses were measured, and the elemental distribution of the stony meteorites was determined via energy dispersion spectroscopy. The study results explain the differences in the ablation and recrystallization process between stony and iron meteorites.

Drift and afterburning effect on rocket exhaust plume impingement and optimization of deflector

This paper studies the one-nozzle liquid rocket exhaust plume impinging on the flame deflector. The effect of drift and afterburning on exhaust plume impinging on the deflector during the takeoff phase is studied by numerical simulation. An impact model is established based on three-dimensional compressible Navier-Stokes equations, a two-equation realizable k-epsilon turbulence model, an afterburning model, and second-order total variation diminishing upwind scheme. The study shows that the smoothness of the deflector discharge is affected by the impingement position of the exhaust plume impinging on the deflector due to the drift of such a position during the take-off phase of the rocket. The temperature of the rocket exhaust plume flow field after considering the chemical reactions is higher than that of the frozen flow, and the temperature of the deflector surface is also higher than that of the frozen case. With the increase of the impingement angleat inlet areaof the rocket exhaust plume impinging on the deflector, the deflector discharge performance gradually decreases. At the same impingement angleat inlet area, as the impingement angleat exit areadecreases, the deflector slot discharges more smoothly.

Modeling of heat transfer in target material during the electron beam evaporation process

Numerical simulation provides a new method to study the heat and mass transfer behavior during the electron beam evaporation (EBE) process, which can obtain some physical quantities that cannot be accurately measured in experiments. In this study, a mathematical model is established to investigate the evaporation behavior, the variation of temperature field and flow field of target material during the EBE process, and verified through experiments. The results show that the evaporation rate of target material is extremely non-uniform on the molten pool surface, which the calculation error of the evaporation rate was 2.78 %. The solid-liquid interface obtained by numerical simulation is basically consistent with the experiment, which the calculation error of the molten pool depth was 3.57 % and the calculation error of the molten pool width was 1.18 %. In addition, the surface temperature and flow rate of the molten pool increased with the increase of the electron beam power, the depth and the width of the molten pool increased linearly with the increase of the electron beam power and then level off. The model can accurately describe the variations of temperature field and flow field during the EBE process, and then make reliable predictions based on the simulation results.

Numerical investigation of conjugate heat transfer in a heat exchanger equipped with cross-combined ellipsoidal dimple tubes

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-? 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.

Multi-physical field simulation calculation and analysis of simulated high-level waste liquid spray calcination.

Aiming at the independent research and development of a simulated high-level waste liquid spray calcination transformation treatment test device, a three-dimensional multi-physical field model of spray calcination was established by means of finite element analysis method. In this paper, the simulated high-level waste liquid is a mixed solution of nitrate solution and sucrose. The main chemical components of nitrate dissolution are HNO3 and NaNO3. The process of evaporation and calcination of high-level waste liquid to form oxides is also called the pretreatment of high-level waste liquid or the conversion of high-level waste liquid. In this experiment, the atomized droplets sprayed at high speed are evaporated, dried and calcined in turn in the calciner to obtain the calcined product. The distribution law of temperature flow field and chemical reaction state and results inside the test device were revealed by simulation calculation. The results show that under the condition of multi-physical field coupling, the chemical reaction temperature has an effect on the yield of the product. The temperature is positively correlated with the product concentration, and the effect of temperature on the yield of NO2 is greater than that of Na2O. At the same time, in this chemical reaction, the concentration of reactants (NaNO3 and HNO3) had a positive correlation with the concentration of main products (NO2 and Na2O). However, the rate of increase in the concentration of the main products (NO2 and Na2O) decreased with the increase of the concentration of the reactants (NaNO3 and HNO3).

Analysis of heat charging and release processes in cascade phase change materials energy storage floor heating systems: Performance evaluation

To address the issues of high energy consumption, significant temperature fluctuation and low heat release efficiency in conventional energy storage floor heating systems, this study proposes a novel solution known as the cascade energy storage floor heating system. This system incorporates two layers of phase change materials (PCMs) with distinct phase change temperatures as the thermal energy storage medium. A coupled heat transfer numerical model is developed to analyze the heat charging and release processes within the floor heating system. The evolutions of liquid fraction of PCMs, flow field and floor surface temperature are investigated during the heat charging and release processes. The findings demonstrate that the cascade PCM energy storage floor heating system avoids overheating and saves >19 % of energy consumption during the heat charging process, elevates the floor surface temperature by about 2 K during the late stage of heat release and thus reduces floor surface temperature fluctuation in comparison with the single-stage PCM system. These improvements are conducive to enhancing the energy utilization rate. Due to better synergistic solidification of the two PCM layers, the system with a PCM proportion of 1:1 exhibits superior overall heat release performance when compared to systems with PCM proportions of 1:2 or 2:1. The research outcomes provide a theoretical foundation and technical guidance for the practical implementation of cascade PCM energy storage technology in the field of building energy conservation.

Characteristics of cavitating flows in cryogenic pump units in a combined cycle power system based on liquefied natural gas and solar energy

The cavitation of cryogenic pump units is an important cause for the low cold energy recovery efficiency and low utilization efficiency of solar energy in combined cycle power systems based on liquefied natural gas (LNG) and solar energy. Through numerical simulation of cavitation in cryogenic pump units, the research established the correlation mechanism between cavitation evolution and energy characteristics. By using the transport-based cavitation model considering the thermomechanical effect of cryogenic media, a novel numerical simulation model for two-phase flows during cryogenic cavitation was developed. In addition, the numerical model of cavitation was verified to be reliable. The cavitation performance of the two-stage LNG submerged pump in cryogenic pump units was studied under multiple conditions. In addition, the evolution of cavitating flow regimes under conditions of different flow rates and its influences on flow patterns of various flow passage components were investigated by combining analysis on temperature changes and flow fields. The entropy production diagnostic model (EPDM) was also adopted to discuss the distribution of the irreversible entropy production rate (EPR) in the evolution process of cavitation. Results show that the interfacial EPR that characterizes the phase-transition intensity after inception of cavitation exerts significant influences. Analysis of influencing mechanisms of changes in temperature, changes in flow fields, and distribution characteristics of energy consumption can provide a theoretical basis for further optimization.

Numerical simulation of flow and heat transfer in fuel assembly of floating nuclear power platform

ABSTRACT Floating nuclear power platform (FNPP), unlike onshore nuclear power plants, is subjected to periodic rolling loads at sea. These loads will have a more obvious impact on the flow characteristics and temperature distribution inside the fuel assembly (FA). This paper first establishes a refined model of the 7 × 7 core fuel assembly. Then, the flow and heat transfer characteristics of assembly with pure fuel bundles and assembly with guide tubes are analyzed using a segmented grid partitioning method, taking into consideration both accuracy and efficiency in calculation. Finally, the flow and heat transfer characteristics inside the assembly with guide tubes under rolling conditions are simulated and calculated, and compared with the previous simulation results. The calculation results show that the flow and heat transfer characteristics of the assembly with guide tubes are quite different from those of the pure fuel rod bundle assembly, and the rolling environment has obvious adverse effects on the flow field characteristics and temperature distribution in the fuel assembly of the offshore reactor, which must be considered in the design and construction of the floating nuclear power platform. The research results have significant reference value for the design and optimization of floating nuclear power platform assemblies under rolling conditions.

Efficient sound modeling for acoustic monitoring in complex temperature and wind fields

Active monitoring of atmospheric processes, combustion characteristics in burning furnaces, and various industrial applications relies on precise reconstruction of temperature and medium flow fields. This paper derives a novel trajectory equation for modeling sound wave trajectories within complex temperature and wind fields. Unlike traditional ray-equations widely used in dynamic media, the newly formulated trajectory equation is based on the propagation distance rather than the sound wave's time of flight. This alteration directly incorporates trajectory curvature, facilitating the development of efficient path tracing algorithms. In scenarios where wind speed is significantly lower than the Laplace sound speed and the wavefront's normal direction aligns closely with the sound wave's propagating direction, a simplified trajectory equation is derived. We develop a shooting method to numerically solve both the general and simplified trajectory equations. The fourth-order Runge-Kutta method (RK4) is employed, known for its high accuracy with a local fifth-order truncation error. A benchmark test, utilizing an analytically known path for the sound wave, confirms the shooting method's high precision. One notable strength of this approach lies in its computational efficiency. Tracing sound trajectories originating from a single source is achieved within seconds or tens of seconds on standard personal computers across various numerical examples. Furthermore, the shooting method effectively models sound trajectories in complex temperature and wind fields, such as those encountered in the near-surface atmosphere and high-temperature furnaces. Due to their efficiency and accuracy, the newly formulated trajectory equations and the accompanying shooting method are not only well suited for acoustic modeling, as demonstrated in this study, but are also poised for seamless integration into acoustic tomography systems in future studies.

Influence of temperature on the radon concentration distribution in ramp under low-speed wind field: A numerical simulation study

By introducing the parameters of radon exhalation rate and radon diffusion coefficient, the distribution of radon concentration field on ramp under the condition of superposition of temperature field and flow field is simulated. The simulation results show that the distribution of radon concentration in the ramp under the condition of low-speed ventilation is greatly affected by the temperature field and flow field, and the change of radon exhalation caused by temperature is the main factor leading to the change of radon concentration in the ramp. The change of temperature will cause the overall increase of radon concentration in the ramp. Under the condition of constant flow field, the radon concentration in the chamber is more than two times higher than the average radon concentration in the ramp. Some areas severely exceeded the limit.

Effect of fluid-particle interaction on 2D Rayleigh-Bénard laminar convection of a temperature-sensitive magnetic fluid

Rayleigh-Bénard (R–B) laminar convection of a temperature-sensitive magnetic fluid (TSMF) with an immersed nonmagnetic particle in a square cavity heated from the bottom and subject to an external magnetic field is investigated experimentally and numerically, which restricts to the initial constant temperature and stationary flow fields with perfect thermal insulated wall condition. The flow and particle behaviors as well as the heat transfer characteristic are examined at different Ra (Ra < 4 × 104) and Ram (Ram = 0, 1.89 × 108, and 3.14 × 108). The magnetic field slightly precipitates the onset of convection and the transition of the flow pattern. The particle may influence the early flow development and the final flow pattern, depending on the initial location of the particle, Ra, and Ram. Over certain ranges of the parameters, the particle stabilizes the flow by shifting the higher flow mode (bicellular) to the lower one (unicellular) and improves the heat transfer performance. The numerical results confirm the experimental findings and provide more detailed behaviors of the flow and temperature fields as well as the particle.

Designing jet deflector configuration for a semi-cryogenic rocket engine

This study deals with the design of a suitable configuration of jet deflector for supersonic exhaust gases from a semi-cryogenic launch vehicle engine using computational fluid dynamics. Computational model of combustion in semi-cryogenic engine, with kerosene as fuel and liquid oxygen as oxidizer, was developed in which exhaust gases from engine were impinged on the deflector surface. Different design configurations of deflector structure, obtained by the combination of various impingement angles of 15°, 20°, 25°, 30°, and 45°, and different exit radii of 5000, 10 000, and 20 000 mm, were used in the developed computational models to analyze impingement, deflection, and associated flow properties of exhaust gases, such as acoustics, force on deflector imparted by jet, temperature, and Mach number of flow field. A new ablation model was developed based on Vieille's law to determine the amount of refractory material ablated from deflector structure for different configurations. The developed models of ablation, combustion, and flow impingement were also validated with existing literature. It was found that the configuration with 20° impingement angle and 10 000 mm exit radius had ablation, acoustics, force, and flow properties in desired limit. Furthermore, to find the optimum uplift angle for designing jet deflector, configurations with uplift angles of 0°, 5°, 15°, and 25° were studied using the computational models developed in the study. It was observed that the configuration with 20° impingement angle, 10 000 mm exit radius, and 15° uplift angle was best suited for impingement and deflection of exhaust jet from the specified semi-cryogenic engine.

The numerical investigation of cladding layer forming process in laser additive manufacturing with wire feeding

Laser additive manufacturing with wire feeding is extensively applied in the numerous fields such as rail transit, aerospace and biomedical since the high efficiency and flexibility. The formed cladding layer has great influence on determining the quality of manufactured products during the additive manufacturing process. Therefore, a three-dimensional numerical model is developed in this paper to analyze the molten metal behaviors and the cladding layer formation process in the laser additive manufacturing with wire feeding by 316L stainless steel wire. The calculated temperature field and flow field of the molten pool are analyzed and discussed in detail. It is found that the molten metal is transported into molten pool periodically in the droplet shape along the 316L stainless steel wire and then solidified gradually as the cladding layer with the corrugated surface. The simulated results are kept consistent with experimental results from the literatures. The proposed model is of great importance for obtaining the desired cladding layer and is efficient for improving the laser additive manufacturing quality.