scholarly journals Computational and Mathematical Model with Phase Change and Metal Addition Applied to GMAW

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Alfredo dos Santos Maia Neto ◽  
Marcelo Gonçalves de Souza ◽  
Edson Alves Figueira Júnior ◽  
Valério Luiz Borges ◽  
Solidônio Rodrigues de Carvalho
Keyword(s):  
Mathematical Model ◽  
Phase Change ◽  
Thermal Model ◽  
Complex Geometry ◽  
Golden Section ◽  
Simulated Data ◽  
Heat Diffusion ◽  
Data Logger ◽  
Heat Diffusion Equation ◽  
Metal Addition

This work presents a 3D computational/mathematical model to solve the heat diffusion equation with phase change, considering metal addition, complex geometry, and thermal properties varying with temperature. The finite volume method was used and the computational code was implemented in C++, using a Borland compiler. Experimental tests considering workpieces of stainless steel AISI 304 were carried out for validation of the thermal model. Inverse techniques based on Golden Section method were used to estimate the heat transfer rate to the workpieces. Experimental temperatures were measured using thermocouples type J—in a total of 07 (seven)—all connected to the welded workpiece and the Agilent 34970A data logger. The workpieces were chamfered in a 45° V-groove in which liquid metal was added on only one weld pass. An innovation presented in this work when compared to other works in scientific literature was the geometry of the weld pool. The good relation between experimental and simulated data confirmed the quality and robustness of the thermal model proposed in this work.

Merits of Employing Foam Encapsulated Phase Change Materials for Pulsed Power Electronics Cooling Applications

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
K. Lafdi ◽  
O. Mesalhy ◽  
A. Elgafy
Keyword(s):  
Phase Change ◽  
Heat Sink ◽  
Phase Change Materials ◽  
Electronics Cooling ◽  
Volume Averaging ◽  
Equation Model ◽  
Heat Diffusion ◽  
Solid Matrix ◽  
Design Parameters ◽  
Heat Diffusion Equation

In the present work, the potential of using foam structures impregnated with phase change materials (PCMs) as heat sinks for cooling of electronic devices has been numerically studied. Different design parameters have been investigated such as foam properties (porosity, pore size, and thermal conductivity), heat sink shape, orientation, and use of internal fins inside the foam-PCM composite. Due to huge difference in thermal properties between the PCM and the solid matrix, two energy equation model has been adopted to solve the energy conservation equations. This model can handle local thermal nonequilibrium condition between the PCM and the solid matrix. The numerical model is based on volume averaging technique, and the finite volume method is used to discretize the heat diffusion equation. The findings show that, for steady heat generation, the shape and orientation of the composite heat sink have significant impact on the system performance. Conversely, in the case of power spike input, use of a PCM with low melting point and high latent heat is more efficient.

Various Approaches to Numerical Discretization of Thermal Model With Phase Change

2015 ◽  
Author(s):  
Tomas Mauder ◽  
Lubomir Klimes ◽  
Pavel Charvat ◽  
Josef Stetina
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Model ◽  
Phase Change Materials ◽  
Heat Diffusion ◽  
Food Freezing ◽  
Wide Range ◽  
Comfort Food ◽  
Numerical Discretization ◽  
Transfer Problems

Phase change materials are nowadays used in a wide range of technical applications such as energy storage, building temperature comfort, food-freezing, etc. The accurate modelling of this process is important for the performance and usability of many technologies. Analytical solutions can be used only for simple heat transfer problems which make the numerical methods the only possible way how to deal with complex multidimensional cases. This paper deals with the comparison of commonly used numerical schemes for heat diffusion with phase change and its parallel computation possibilities.

Mathematical modelling of temperature profile of volcanic soils affected by an external thermal impact

Soil Research ◽  
2006 ◽  
Vol 44 (1) ◽  
pp. 57 ◽  
Author(s):  
Mónica Antilén ◽  
Olivier Fudym ◽  
Alvaro Vidal ◽  
Juan E. Foerster ◽  
Nelson Moraga ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Soil Temperature ◽  
Temperature Profile ◽  
Soil Surface ◽  
Heat Diffusion ◽  
Volcanic Soils ◽  
Heat Diffusion Equation ◽  
Transient Heat Diffusion ◽  
Relative Errors ◽  
The Mathematical Model

In this work, the soil temperature at depth was measured in the laboratory, and a mathematical model to fit the temperature profile in volcanic soils classified as Ultisols and Andisols was used. The mathematical model considered the transient heat diffusion equation, and a numerical discrete method was used to solve the equations system. The soil surface was heated for 2500 s and the temperature rose close to 700°C; the soil temperature decreased with depth; the temperature v. time curves showed a constant value when the temperature reached around 100°C, associated with water phase change and related to the water content of soils. The model was corrected by including the heat volumetric formulation. The observed relative errors are close to 10% in all fitted curves with respect to experimental data, showing the quality of the parametrisation chosen in the mathematical model. The fitting curve deviations were reduced when the actual position of thermocouples was considered, showing the sensitivity of the mathematical model. The simplified mathematical transient diffusion model proposed, which considers 2 ranges of thermal conductivity of soils and the surface temperature, was able to describe the experimental temperature profile in volcanic soils with wide differences in mineralogy, organic matter, and moisture contents.

Numerical Simulation of Mark Formation/Erasure in Phase Change Recording

2005 ◽  
Author(s):  
Evan Small ◽  
John Reifenberg ◽  
Yizhang Yang ◽  
Sadegh M. Sadeghipour ◽  
Mehdi Asheghi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Temperature Distribution ◽  
Finite Elements ◽  
Phase Change ◽  
Finite Elements Method ◽  
Heat Diffusion ◽  
Recording Media ◽  
Heat Diffusion Equation ◽  
Heat Transfer Simulation

Design/optimization of the phase change recording media to create proper marks, in size, shape, and quality, needs a robust modeling tool to predict temperature distribution in the constituting layers and model the phase formation during writing/erasure of the information bits. This requires a modeling of the heat transfer (thermal performance) and the crystallization processes. The thermal modeling, which is based on the solution of the heat diffusion equation for finding temperature distribution in the multilayer media, has been done before, using the finite difference techniques. These techniques have limited potentials for modeling real phase change recording media that have a rather more complex geometry. The finite elements method has, on the other hand, the required flexibility for such applications. In this work, we are reporting on development of a numerical simulation tool that uses the finite elements method for heat transfer simulation. ANSYS is used as the source code for the heat transfer simulation, in this application, with the crystallization model then being built into this media. This code has been used to simulate mark formation during writing on grooved plain and planer patterned media. Patterning the phase change material layer looks very promising in controlling the mark size and the mark edge irregularity which lead to timing jitter.

scholarly journals Numerical and experimental investigation of the thermal and electrical characteristics of a lithium ion cell

2021 ◽  
Vol 321 ◽  
pp. 03007
Author(s):  
Tanılay Özdemir ◽  
Özgür Ekici ◽  
Murat Köksal
Keyword(s):  
Temperature Variation ◽  
Thermal Model ◽  
Coupled Model ◽  
Negative Electrode ◽  
Lithium Ion ◽  
Heat Diffusion ◽  
Maximum Temperature ◽  
Heat Diffusion Equation ◽  
3 Dimensional ◽  
Mean Square Errors

In this study, an electrochemical-thermal coupled model was developed to investigate the electrical and thermal behaviors of the commercial NCR18650b Li-ion cell during three different discharge rates. The 1-dimensional electrochemical model consists of a positive electrode, electrolyte, and a negative electrode and employs the related mass and charge transfer equations for both solid and liquid phases predicting the cell's voltage variation. The 3-dimensional thermal model involves a mandrel, an active battery part, and a shell. The thermal model solves the general heat diffusion equation and predicts the temperature variation of the cell. The results show that the predicted temperature-voltage profiles follow the same trend with experimental data and are consistent. The maximum calculated root mean square errors are obtained as 0.11 V for voltage, and 0.96 °C for temperature predictions. On the other hand, the maximum temperature differences within the cell was found to be 0.16 °C, 0.43 °C, and 1.29 °C after the 0.5 C, 1C and 1.5 C rate discharging processes, respectively. Finally, the results from the 3-dimensional thermal model reveal that the type of mandrel affects the temperature variation within the cell. However, the average surface temperature of the cell remains comparable for the investigated C rates.

Analyzing the Impact of Healthy Behavior on Weight Change with a Provable Mathematical Model (Preprint)

2020 ◽  
Author(s):  
Ayan Chatterjee ◽  
Ram Bajpai ◽  
Pankaj Khatiwada
Keyword(s):  
Physical Activity ◽  
Mathematical Model ◽  
Health Behavior ◽  
Weight Change ◽  
Simulated Data ◽  
Negative Behavior ◽  
Healthy Behavior ◽  
Healthy Habits ◽  
Lifestyle Diseases ◽  
The Impact

BACKGROUND Lifestyle diseases are the primary cause of death worldwide. The gradual growth of negative behavior in humans due to physical inactivity, unhealthy habit, and improper nutrition expedites lifestyle diseases. In this study, we develop a mathematical model to analyze the impact of regular physical activity, healthy habits, and a proper diet on weight change, targeting obesity as a case study. Followed by, we design an algorithm for the verification of the proposed mathematical model with simulated data of artificial participants. OBJECTIVE This study intends to analyze the effect of healthy behavior (physical activity, healthy habits, and proper dietary pattern) on weight change with a proposed mathematical model and its verification with an algorithm where personalized habits are designed to change dynamically based on the rule. METHODS We developed a weight-change mathematical model as a function of activity, habit, and nutrition with the first law of thermodynamics, basal metabolic rate (BMR), total daily energy expenditure (TDEE), and body-mass-index (BMI) to establish a relationship between health behavior and weight change. Followed by, we verified the model with simulated data. RESULTS The proposed provable mathematical model showed a strong relationship between health behavior and weight change. We verified the mathematical model with the proposed algorithm using simulated data following the necessary constraints. The adoption of BMR and TDEE calculation following Harris-Benedict’s equation has increased the model's accuracy under defined settings. CONCLUSIONS This study helped us understand the impact of healthy behavior on obesity and overweight with numeric implications and the importance of adopting a healthy lifestyle abstaining from negative behavior change.

scholarly journals Thermal model with phase change for process parameter determination in laser surface processing

2010 ◽  
Vol 5 ◽  
pp. 395-403 ◽  
Author(s):  
E. Ukar ◽  
A. Lamikiz ◽  
L.N. López de Lacalle ◽  
S. Martinez ◽  
F. Liébana ◽  
...  
Keyword(s):  
Phase Change ◽  
Thermal Model ◽  
Process Parameter ◽  
Laser Surface ◽  
Parameter Determination ◽  
Surface Processing

Infiltration in Unsaturated Frozen Soil

1984 ◽  
Vol 15 (4-5) ◽  
pp. 243-252 ◽  
Author(s):  
Helén Engelmark
Keyword(s):  
Mathematical Model ◽  
Simulated Data ◽  
Frozen Soil ◽  
Thermal Parameters ◽  
Field Observations ◽  
Snow Melt ◽  
One Dimensional ◽  
Run Off ◽  
Melt Infiltration

A one-dimensional mathematical model is used to simulate the process of snow-melt infiltration in unsaturated frozen silt. Hydraulic and thermal parameters are mainly based on data given in the literature. Field observations in a watershed (of area 1.8 km2) are compared with simulated data and consequences on snow melt run-off are discussed.

Mapping Thickness Dependent Thermal Conductivity of GaN

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Elbara Ziade ◽  
Jia Yang ◽  
Gordie Brummer ◽  
Denis Nothern ◽  
Theodore Moustaks ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pump Beam ◽  
Continuous Wave ◽  
High Electron Mobility Transistors ◽  
Heat Diffusion ◽  
Phase Lag ◽  
High Electron ◽  
Heat Diffusion Equation ◽  
Phase Images ◽  
Gan Film

Frequency domain thermoreflectance (FDTR) is used to create quantitative maps of thermal conductivity and thickness for a thinning gallium nitride (GaN) film on silicon carbide (SiC). GaN was grown by molecular beam epitaxy on a 4H-SiC substrate with a gradient in the film thickness found near the edge of the chip. The sample was then coated with a 5 nm nickel adhesion layer and a 85 nm gold transducer layer for the FDTR measurement. A piezo stage raster scans the sample to create phase images at different frequencies. For each pixel, a periodically modulated continuous-wave laser (the red pump beam) is focused to a Gaussian spot, less than 2 um in diameter, to locally heat the sample, while a second beam (the green probe beam) monitors the surface temperature through a proportional change in the reflectivity of gold. The pump beam is modulated simultaneously at six frequencies and the thermal conductivity and thickness of the GaN film are extracted by minimizing the error between the measured probe phase lag at each frequency and an analytical solution to the heat diffusion equation in a multilayer stack of materials. A scanning electron microscope image verifies the thinning GaN. We mark the imaged area with a red box. A schematic of the GaN sample in our measurement system is shown in the top right corner, along with the two fitting properties highlighted with a red box. We show the six phase images and the two obtained property maps: thickness and thermal conductivity of the GaN. Our results indicate a thickness dependent thermal conductivity of GaN, which has implications of thermal management in GaN-based high electron mobility transistors.

Fast Fluid Thermodynamics Simulation by Solving Heat Diffusion Equation

2021 ◽  
Vol 11 (04) ◽  
pp. 1-11
Author(s):  
Wanwan Li
Keyword(s):  
Diffusion Equation ◽  
Real Time ◽  
Stokes Equations ◽  
Fluid Simulation ◽  
Heat Diffusion ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Heat Diffusion Equation ◽  
Acceleration Techniques ◽  
Speed Up

In mechanical engineering educations, simulating fluid thermodynamics is rather helpful for students to understand the fluid’s natural behaviors. However, rendering both high-quality and realtime simulations for fluid dynamics are rather challenging tasks due to their intensive computations. So, in order to speed up the simulations, we have taken advantage of GPU acceleration techniques to simulate interactive fluid thermodynamics in real-time. In this paper, we present an elegant, basic, but practical OpenGL/SL framework for fluid simulation with a heat map rendering. By solving Navier-Stokes equations coupled with the heat diffusion equation, we validate our framework through some real-case studies of the smoke-like fluid rendering such as their interactions with moving obstacles and their heat diffusion effects. As shown in Fig. 1, a group of experimental results demonstrates that our GPU-accelerated solver of Navier-Stokes equations with heat transfer could give the observers impressive real-time and realistic rendering results.

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