Simulation Of Temperature Distribution Research Articles

Numerical simulation and experimental investigation of temperature distribution during the wire arc additive manufacturing (WAAM) process

Numerical simulation and experimental investigation of temperature distribution during the wire arc additive manufacturing (WAAM) process

High Intensity Focused Ultrasound (20MHz) and Cryotherapy as Therapeutic Options for Granuloma Annulare and Other Inflammatory Skin Conditions.

In dermatology, inflammatory skin conditions impose a substantial burden worldwide, with existing therapies showing limited efficacy and side effects. This report aims to compare a novel immunological activation induced by hyperthermic 20MHz high intensity focused ultrasound (HIFU) with conventional cryotherapy. The bioeffects from the two methods are initially investigated by numerical models, and subsequently compared to clinical observations after treatment of a patient with the inflammatory disease granuloma annulare (GA). Clinical responses to moderate energy HIFU and cryotherapy were analysed using numerical models. HIFU-induced pressure and heat transfer were calculated, and a three-layer finite element model simulated temperature distribution and necrotic volume in the skin. Model output was compared to 22 lesions treated with HIFU and 10 with cryotherapy in a patient with GA. Cryotherapy produced a necrotic volume of 138.5mm3 at - 92.7°C. HIFU at 0.3-0.6J/exposure and focal depths of 0.8 or 1.3mm generated necrotic volumes up to only 15.99mm3 at temperatures of 68.3-81.2°C. HIFU achieved full or partial resolution in all treated areas, confirming its hyperthermic immunological activation effect, while cryotherapy also resolved lesions but led to scarring and dyspigmentation. Hyperthermic immunological activation of 20MHz HIFU shows promise for treating inflammatory skin conditions as exemplified by GA. Numerical models demonstrate minimal skin necrosis compared to cryotherapy. Suggested optimal HIFU parameters are 1.3mm focal depth, 0.4-0.5J/exposure, 1mm spacing, and 1mm margin. Further studies on GA and other inflammatory diseases are recommended.

Transient Heat Transfer Analysis in Metal Plates with Variable Thickness

Nonlinear transient heat transfer via conduction–radiation is a dynamic topic of long-standing interest with applications ranging from aeronautical and mechanical engineering to industrial and civil security. To gain a better understanding of the performances of materials having thermal proprieties that change during nonlinear heat transfer, several studies using the finite element method (FEM) have been conducted. Such studies apply nonlinear thermal material characteristics to describe the complete system under different loading conditions in each region by adjusting the temperature values for the other three edges and the thickness parameter with Dirichlet boundary conditions. As a result, while modeling and simulating temperature distributions for such situations, nonlinearities generated by temperature-dependent thermal conductivity must be considered. In this work, we focus on the analysis of coupled transient heat transfer through two metal plates with temperature-dependent thermal characteristics in which the temperature is fixed along the bottom edge and heat is transferred from both the top and bottom faces of the two plates. FEM is employed to solve the nonlinear heat equation and compute the temperature as a function of time for variable thickness. The study examines the effect of modifying the thickness parameter values on the temperature distribution over time for various edge values over 5,000 s.

Numerical Simulation of Airflow Velocity and Temperature Distribution in an Aircraft Cabin

In this work, a computational fluid dynamics (CFD) model is established to calculate the airflow distribution in the cabin of a single-channel Boeing 737-800 airplane. The RNG k-ε model, considering the calculation of turbulence kinetic energy and its rate of dissipation, is adopted to solve turbulence problems in physical field simulation. The proposed three-dimensional model is able to consider the particular physical factors and spatial structures, which can simulate the detailed distributions of complex physical fields, compared with the one-dimensional lumped parameter model. The velocity and temperature fields under different air supply velocities are then numerically investigated. The calculation results show that when the air velocity at the top air supply inlet is 1.4 m/s, the velocity and temperature distribution inside the cabin can both meet the comfort requirements of humans in the airworthiness standards. The results from this work can help to design an aircraft environmental control system.

Analysis of Anthropogenic Waste Heat Emission from an Academic Data Center

The rapid growth in computing and data transmission has significant energy and environmental implications. While there is considerable interest in waste heat emission and reuse in commercial data centers, opportunities in academic data centers remain largely unexplored. In this study, real-time onsite waste heat data were collected from a typical academic data center and an analysis framework was developed to determine the quality and quantity of waste heat that can be contained for reuse. In the absence of a comprehensive computer room monitoring system, real-time thermal data were collected from the data center using two arrays of thermometers and thermo-anemometers in the server room. Additionally, a computational fluid dynamics model was used to simulate temperature distribution and identify “hot spots” in the server room. By simulating modification of the server room with a hot air containment system, the return air temperature increased from 23 to 46 °C and the annual waste heat energy increased from 377 to 2004 MWh. Our study emphasizes the importance of containing waste heat so that it can be available for reuse, and also, that reusing the waste heat has value in not releasing it to the environment.

Effect of flow pulsation on heat transfer performance of biomimetic bark microchannel heat sink

Pumping coolant or using pulse flow through microchannels with novel structures on microelectronic devices is suitable for high heat flux dissipation and sensor development. This study proposes a novel microchannel designed as a series of biomimetic bark channel networks. Simulation and experimental testing of temperature distribution and heat transfer performance are conducted under different working conditions, including various fluid parameters. The results show that combining biomimetic bar microchannel and pulsation flow can improve heat transfer performance. The effect of pulsating flow frequency on the temperature is only evident outside the range of 10 mm from the inlet. Compared with non-slip boundaries, the boundary slip of pulsating flow slightly enhances heat transfer. Pulsating flow has an optimal frequency, minimizing thermal resistance for different inlet temperatures.

Simulation and experimental study of temperature and mass distributions of indium metal in vacuum evaporation

The temperature field and spatial distribution of metal vapor (i.e., flow field) are critical for the purity and direct yield of metals. However, it is impossible to accurately determine the temperature field and distribution of the metal vapor in a vacuum furnace. This study developed a surface-to-surface thermal radiation and volume of fluid multiphase flow coupling model. The temperature distribution and mass distribution of indium vapor in the vertical vacuum furnace at different temperatures from 1423 to 1573 K under the condition of 1 Pa were obtained. The reliability of the model was verified by experimental data obtained under the same conditions as the simulation. The temperature difference between the inside and outside of the condensing plate was 30–45 K in the temperature interval of 1423–1573 K. The temperature difference between the inside wall and the center of the condensing plate was 10 K. The simulation results of indium vapor mass distribution match with the experimental values; the overall temperature error is 5%, and the volatility error is less than 15%. The model developed in this study can be used to predict the temperature field and metal vapor distribution in a vacuum furnace, which will significantly reduce experimental exploration and accurately guide the production practice of vacuum metallurgy. This will expand the application of vacuum metallurgy technology in metal purification, material preparation, waste recycling, and other industries. This can effectively reduce exploratory experiments in the process of vacuum distillation to prepare high-purity metals, reduce the consumption of resources and energy in the experiment and production process, and achieve clean production.

Molecular dynamics simulation of temperature and concentration distribution at liquid-gas interface during liquid air storage process

To address global challenge of climate changes, renewable energy has been fully developed in recent years. However, renewable energy is usually intermittent which makes it challenging for application. Liquid air energy storage can effectively store intermittent energy with promising prospects. Liquid air is a mixture composed of N2, O2 and Ar with different evaporation temperatures. It is assumed to form temperature and concentration stratification during storage and thus causes safety challenge. To address this issue, molecular dynamics (MD) simulation method is used to study the temperature and concentration distribution characteristics in liquid air. The results show that the system temperature remains constant at 94 K with no temperature stratification during storage. However, the concentration of liquid air changes along vertical direction (z axis): the oxygen concentration remains stable around 21% as z is 0-60 Å, rises to 22.1% as z is from 60-70 Å and drops to 0% as z is above 80 Å. The thin and short stratification phenomenon occurs at the gas-liquid interface region. In addition, a higher heat flux leads to a higher evaporation rate and a larger oxygen concentration. As the heat flux increases from 0.0 to 2.4 W/m2, evaporation rate rises from 0.13 to 0.2% and the oxygen concentration at the liquid-gas interface reaches 22.3%. Thus, concentration stratification exists during liquid air storage and should be treated carefully. This paper provides an insight into the temperature and concentration distribution of liquid air during storage and is significant for safety improvement and development of liquid air energy storage.

An accelerated lattice Boltzmann method for natural convection coupled with convolutional neural network

A novel approach is proposed in the present study, which combines the lattice Boltzmann method (LBM) with convolutional neural networks and is suitable for square cavity natural convection and conjugate natural convection problems, exhibiting remarkable acceleration capabilities and potentials. The density distribution function obtained from LBM at time t and the temperature distribution function at time t+Δt under different Rayleigh numbers (Ra) are, respectively, utilized as input and output datasets for training and comparison in three convolutional neural networks, aiming to select the optimal coupling model, namely, half-Res-Unet. The coupling model can accurately simulate the natural convection in a square cavity within six times the upper limit of the Ra under the training condition, which can save the central processing unit (CPU) calculation time and the iteration steps by up to 29.2% and 30.3%, respectively. The coupling model is further extended in the current study to incorporate conjugate natural convection, enabling the accurate simulation of temperature distribution under training conditions with a thermal conductivity ratio (Ka) of 25 and an upper limit of Ra increased by 20 times. The corresponding maximum relative errors for the average Nusselt numbers (Nu) are found to be 1.8% and 0.7%, respectively, providing strong evidence for the generalization capability of the coupling model. Furthermore, the coupling model demonstrates a remarkable acceleration performance, as evidenced by its ability to reduce the CPU calculation time by up to 39.6% and iteration steps in the simulation process by 36.5%. It offers valuable insights into the integration of LBM with machine learning techniques, thereby enhancing the computational efficiency of LBM.

Development of a microwave chemical cell coupled with post-wall waveguide for in situ/operando soft x-ray absorbance spectroscopy under microwave irradiation

In this study, we developed a microwave chemical cell for total electron yield soft x-ray absorption spectroscopy (XAS) using synchrotron radiation under microwave irradiation. In addition, in situ XAS measurements of ammonia borane were performed using the device developed. The device comprises a post-wall waveguide housing a sample holder formed within it. Electrons emitted from the sample during soft x-ray irradiation pass through the metal plates of the waveguide and are measured using a picoammeter. Integration of the microwave irradiation structure into a synchrotron radiation beamline, which is a challenge in soft x-ray analysis requiring measurements in a high-vacuum atmosphere, was achieved by miniaturizing the device using 24.125 GHz ISM band microwaves, instead of the typical 2.45 GHz microwaves. Performance of the device was thoroughly assessed through temperature distribution simulation, temperature measurement of water, and evaluation of frequency characteristics. When the sample holder was filled with water and irradiated with 3 W microwaves, the temperature increased to 97 °C, which is close to the boiling point. The in situ XAS measurements performed using this device with ammonia borane/graphite (2:1) powder at the B-K edge during microwave irradiation showed that peaks associated with hydrogen desorption intensified with prolonged microwave exposure. This result indicates that microwave heating in a vacuum and soft x-ray analysis during microwave heating were achieved. The developed microwave chemical cell emerges as a powerful tool, facilitating advancements in our understanding of elementary chemical processes and elucidating microwave-specific effects such as local heating during microwave irradiation.

Simplified Simulation Method of Diffusers for Indoor Non-Uniform Temperature Distribution: A Case Study in Shanghai

The specific air jet of a diffuser is formed by the complex internal structure, which affects the outlet airflow distribution of the diffuser directly and the indoor environment distribution indirectly. If the diffusers are developed based on their actual geometry structure and their boundary conditions are set as their inlet flowrate, the simulated indoor temperature distribution will be more accurate. However, it is noted that many problems may arise, such as model complexity, many grid cells, and slow convergence of calculations. Therefore, this paper focuses on a simplified method for four-way square diffusers in a computational fluid dynamics (CFD) simulation of indoor non-uniform temperature distribution. Firstly, the airflow distribution is simulated on the outlet air supply cross-section of the diffuser. Then, according to the outflow characteristics of the diffuser, the diffuser model is simplified and simulated in an experimental room. Finally, the temperature distribution at the 1.2 m height plane is obtained from CFD simulation and compared with the experimental results. The results show that the 68-point air supply opening model can well simulate the effects of the outlet airflow distribution of the diffuser, and the simulated indoor temperature distribution meets the experiment results well. The deviations for three scenarios are between −7.4~1.7% and the average deviation is −3.0%, while the root mean square error of temperature for three scenarios is 0.7 °C, 0.7 °C, and 1.0 °C, respectively. The results also demonstrate the mutual influence of the airflow from different diffusers and the indoor non-uniform temperature distribution under the action of multiple diffusers. The proposed method can contribute to balancing the model complexity and the accuracy in CFD simulation, especially for multiple diffusers in the room.

Numerical Simulation of Temperature Distribution in End-Pumped Nd∶YAG with Uniform and Gradient Dopants of Nd3+

Numerical Simulation of Temperature Distribution in End-Pumped Nd∶YAG with Uniform and Gradient Dopants of Nd3+

Optimization analysis of solid oxide fuel cells with ceria-based single cells using computational fluid dynamics

The SOFC simulations in this research are conducted at temperatures of 600°C, 700°C, and 800°C, focusing on the Ni-SDC anode, SDC electrolyte, and LSCF-SDC materials used in the SOFC single cell. Initially, the single-cell model is created using CAD software, followed by the development of a computational fluid dynamics (CFD) model with the requisite material properties. The study then proceeds to simulate temperature distribution and cell performance for various supported SOFC stack models (electrode and electrolyte supported) at intermediate temperatures. Subsequently, the study examines cell performance with varying thicknesses of the anode, electrolyte, and cathode components within the specific supported single cell. In summary, the CFD results indicate that cathode-supported SOFCs exhibit higher power density, specifically 938.28 mW/cm2 at 800°C, surpassing anode-supported and electrolyte-supported configurations. The power density reaches 1495.40 mW/cm2 when the single-cell layer thickness is 0.35 mm for the cathode, 0.02 mm for the anode, and 0.01 mm for the electrolyte. However, electrolyte-supported single cells display the lowest temperature difference, at 0.028% at 800oC The simulation results demonstrate that reducing the thicknesses of all electrodes and the electrolyte leads to increased current density, power density, and temperature distribution difference.

Simulation of Air Flow Field and Temperature Distribution in the Ward of a Newly-Built Hospital of Post-COVID-19

In order to solve the problem of uneven distribution of air conditioning temperature and air velocity in the ward, it is easy to produce the uncomfortable feeling of cold and hot and wind blowing. Taking the standard double room general ward of a newly built hospital as the research object, a mathematical model was established, and CFD software was used to numerically simulate the temperature field and velocity field of the air in the ward, optimize the location of the air outlet, and put forward the suggestion of the optimal installation location of the hospital bed. The results show that when the fan coiler air supply outlet is close to the west wall and the fresh air outlet is far away from the west wall, the inhomogeneity of the distribution of the temperature field and velocity field in the ward is reduced, and at this time, the temperature and velocity distribution of the air in the ward is more uniform, so that the patients’ overall feeling in the ward is more comfortable, and at this time, the installation position of the air outlet is more reasonable; and it is determined that the optimal placement of the beds in the room is at the locations of [Formula: see text] = 2 m, [Formula: see text] = 2.5 m and [Formula: see text] = 2 m, [Formula: see text] = 4.5 m, and at this time the two beds are at the same time, which is more reasonable. When [Formula: see text] = 4.5 m, the temperature difference between the two beds is less than 0.5 K, the wind speed difference is not more than 0.08 m/s, and the velocity gradient direction is the same.

The Temperature Distribution Simulation in the Graphene Sublimation Growth Zone on SiC Substrate

The Temperature Distribution Simulation in the Graphene Sublimation Growth Zone on SiC Substrate

Simulation and enhancement of axial temperature distribution in a reactor filled with in-situ electrically heated structured catalyst

The hydrogen production technology based on the in-situ electrically heated structured catalyst (EHSC) has the advantages of compact structure, fast response, and less CO2 emissions. However, there is still a lack of research on the temperature distribution of the reactor filled with EHSC. Based on the problem, a CFD model was established, and the temperature distribution was revealed. To further reduce the large temperature difference in axial direction, the effects of the gradient-pitch design and segmented-voltage-control design for the EHSC on the temperature distribution and methanol conversion were studied numerically. The results showed that segmented-voltage-control design can significantly reduce the maximum axial temperature difference, due to the fact that the reaction heat and corresponding Joule heat supplied at each axial section were flexibly well matched. When reaction temperature was 275 °C, the maximum temperature difference decreased from 84.7 °C to 31.1 °C. Moreover, when GHSV was 13000 ml/(g h), methanol conversion was improved by up to 10.9%. The segmented voltage control method for the EHSC provides an opportunity to design an isothermal endothermic reactor under any reaction conditions in the case of further optimization of segmented-voltage-control design.

A Generic Approach to Simulating Temperature Distributions within Commercial Lithium-Ion Battery Systems

Determining both the average temperature and the underlying temperature distribution within a battery system is crucial for system design, control, and operation. Therefore, thermal battery system models, which allow for the calculation of these distributions, are required. In this work, a generic thermal equivalent circuit model for commercial battery modules with passive cooling is introduced. The model approach can be easily adopted to varying system designs and sizes and is accompanied by a corresponding low-effort characterization process. The validation of the model was performed on both synthetic and measured load profiles from stationary and marine applications. The results show that the model can represent both the average temperature and the occurring temperature spread (maximum to minimum temperature) with deviations below 1 K. In addition to the introduced full-scale model, further simplifying assumptions were tested in order to reduce the computational effort required by the model. By comparing the resulting simplified models with the original full-scale model, it can be shown that both reducing the number of simulated cells and assuming electrical homogeneity between the cells in the module offer a reduction in the computation time within one order of magnitude while still retaining a high model accuracy.

Thermal-fluid behavior and microstructure morphology during laser melting deposition of TiC/Ti6Al4V functionally graded materials

Laser melting deposition (LMD) is an additive manufacturing technology that involves complex thermodynamic and kinetic characteristics in the molten pool. A perspective on the thermal-fluid dynamic behavior in the molten pool is essential for investigating the microstructure morphology and solidification characterization. In this study, a three-dimensional transient thermal-fluid coupling model is proposed for describing thermal-fluid dynamic behavior within the molten pool during laser melting deposition of TiC/Ti6Al4V functionally graded materials. The simulated temperature distribution and deposition layer morphology agree well with the experimental results. The simulation results indicate that the heat accumulation phenomenon generated during the LMD process can exacerbate the penetration effect of the molten pool. The solidified deposition layer will be remelted to form a large cross-layer molten pool, and the molten metal in the remelted zone will move from the lower layer to the upper layer driven by the Marangoni convection. Furthermore, the unmelted TiC particles and the in-situ generated TiC particles can decrease the free energy of the molten pool, induce heterogeneous nucleation, and promote the growth of equiaxed crystals.

Simulation of Spatiotemporal Distribution and Variation of 30 m Resolution Permafrost in Northeast China from 2003 to 2021

The high-resolution permafrost distribution maps have a closer relationship with engineering applications in cold regions because they are more relative to the real situation compared with the traditional permafrost zoning mapping. A particle swarm optimization algorithm was used to obtain the index η with 30 m resolution and to characterize the distribution probability of permafrost at the field scale. The index consists of five environmental variables: slope position, slope, deviation from mean elevation, topographic diversity, and soil bulk density. The downscaling process of the surface frost number from a resolution of 1000 m to 30 m is achieved by using the spatial weight decomposition method and index η. We established the regression statistical relationship between the surface frost number after downscaling and the temperature at the freezing layer that is below the permafrost active layer base. We simulated permafrost temperature distribution maps with 30 m resolution in the four periods of 2003–2007, 2008–2012, 2013–2017, and 2018–2021, and the permafrost area is, respectively, 28.35 × 104 km2, 35.14 × 104 km2, 28.96 × 104 km2, and 25.21 × 104 km2. The proportion of extremely stable permafrost (<−5.0 °C), stable permafrost (−3.0~−5.0 °C), sub-stable permafrost (−1.5~−3.0 °C), transitional permafrost (−0.5~−1.5 °C), and unstable permafrost (0~−0.5 °C) is 0.50–1.27%, 6.77–12.45%, 29.08–33.94%, 34.52–39.50%, and 19.87–26.79%, respectively, with sub-stable, transitional, and unstable permafrost mainly distributed. Direct and indirect verification shows that the permafrost temperature distribution maps after downscaling still have high reliability, with 83.2% of the residual controlled within the range of ±1 °C and the consistency ranges from 83.17% to 96.47%, with the identification of permafrost sections in the highway engineering geological investigation reports of six highway projects. The maps are of fundamental importance for engineering planning and design, ecosystem management, and evaluation of the permafrost change in the future in Northeast China.

Microwave heating of thin rubbers based on single-ridged waveguide

Microwave heating has been gradually applied to rubber vulcanization. However, it is difficult to process thin rubber using microwaves because of low electromagnetic power loss and rapid heat dissipation. Therefore, in this study, a single-ridged waveguide was designed to efficiently heat thin rubber. First, a single-ridged waveguide was designed and optimized to ensure good wave transmission and a strong electric field, and its energy efficiency was approximately 331.9 times greater than that of multi-mode cavity and 77.9 times greater than that of WR340. Then, a multiphysics model coupling the electromagnetic field and heat transfer in a solid was built to investigate the heating performance. The results of additional experiments showed that the experimental and simulated temperature distributions were consistent. Finally, the effects of the working state, offset of the short-circuited surface, the rubber's thickness and permittivity on the heating performance were investigated, and the vulcanization analyses were discussed.