Three-dimensional Thermal Model Research Articles

Durability of sandwich composites under extreme conditions: Towards the prediction of fire resistance properties based on thermo-mechanical measurements

The main objective of the present study was to develop a fire thermal model able to predict the evolution of the temperature gradient across a sandwich composite structure when exposed to fire. Thermal response of sandwich panels, with glass/polyester skins and balsa core, was investigated under severe temperature conditions as samples were exposed to high temperatures up to 570 °C. Based on experimental measurements, an accurate three-dimensional thermal model was developed using finite element analysis. The obtained predictions of the temperature field are in excellent agreement with the experimental data, showing the importance of combined numerical-experimental analyses. This allowed us to propose a new approach that can be used for the prediction of thermo-mechanical post-combustion properties in a very large number of fire and material scenarios according to its simplicity and robustness.

Estimation of thermal conductivity of silicate melts using three-dimensional thermal resistor network model

The thermal conductivity of silicate melts was evaluated using a thermal resistor network model, which consisted of a diamond lattice. Based on the assumption that the mean free path of phonons is shorter than the interatomic distance, the thermal conductivity of the silicate melts was calculated through a Monte-Carlo simulation based on the non-bridging oxygens to tetrahedral cations (NBO/T) ratio and the ratio of the conductance of silicon with NBOs (CSi-NBO) to that of silicon with bonding oxygens (CSi-BO). For NBO/T<1, the simulated thermal conductivity of the silicate melts was in good agreement with that reported in the literature. Thus, the proposed method and the three-dimensional thermal resistor network model used are suitable for estimating the thermal conductivity of silicate melts.

A three-dimensional thermal model for viscoelastic polymer melt packing process in injection molding

In this study, a 3D weakly compressible viscoelastic flow model with the thermal effect is developed for simulations of the non-isothermal XPP melt packing process. The 3D multi-field coupled model is solved by the collocated finite volume CLEAR algorithm with the AVLSMART scheme. The numerical model is validated against the benchmark problem. The XPP melt packing process in a rectangular cavity is simulated, and the predicted flow-induced birefringence is in agreement with the experimental and numerical results reported in the literature. For a case with a rather complex cavity, the XPP melt packing process in a 3D hemispherical shell cavity is further simulated. The distributions of melt temperatures, flow-induced stresses as well as the corresponding rheological characteristics of XPP melt in 3D cavity are vividly presented, which are difficult to be captured by previous simulations and experiments. Especially, the present model allows the effects of melt temperature and holding pressure on the first normal stress difference and density to be studied. It is shown that with an increase in melt temperature, the absolute values of the first normal stress difference increases slightly and the density decreases gradually, while the high holding pressure improves significantly the first normal stress difference and density. Numerical results demonstrate that the present 3D thermal model is an effective tool for simulating real-world viscoelastic polymer melt packing processes.

Streamline three-dimensional thermal model of a lithium titanate pouch cell battery in extreme temperature conditions with module simulation

In this paper, the development of a three-dimensional (3D) lithium titanium oxide (LTO) pouch cell is presented to first better comprehend its thermal behavior within electrified vehicle applications, but also to propose a strong modeling base for future thermal management system. Current 3D-thermal models are based on electrochemical reactions which are in need for elaborated meshing effort and long computational time. There lacks a fast electro-thermal model which can capture voltage, current and thermal distribution variation during the whole process. The proposed thermal model is a reduce-effort temperature simulation approach involving a 0D-electrical model accommodating a 3D-thermal model to exclude electrochemical processes. The thermal model is based on heat-transfer theory and its temperature distribution prediction incorporates internal conduction and heat generation effect as well as convection. In addition, experimental tests are conducted to validate the model. Results show that both the heat dissipation rate and surface temperature uniformity data are in agreement with simulation results, which satisfies the application requirements for electrified vehicles. Additionally, a LTO battery pack sizing and modeling is also designed, applied and displays a non-uniformity of the cells under driving operation. Ultimately, the model will serve as a basis for the future development of a thermal strategy for LTO cells that operate in a large temperature range, which is a strong contribution to the existing body of scientific literature.

Fast-charging investigation on high-power and high-energy density pouch cells with 3D-thermal model development

In this paper, insight of thermal behavior of lithium-ion batteries under fast-charging profiles is investigated. Although battery thermal behavior has been studied by published models, the reported modeling addresses a specific application: fast-charging applications. Most papers in literature present the fast-charging application from an electrical point-of-view. There, lacks a comprehensive electro-thermal model which can capture both the heat generation, voltage and current variation during the whole fast-charging process. In this study, two charging profiles that are commonly used for fast-charging applications are applied on two lithium-ion chemistries: lithium nickel manganese cobalt oxide (NMC) and lithium titanate (LTO). The first one is designed for high-energy density and the other made for high-power applications. To enlarge the study scope, the batteries have been tested at three environmental temperatures: 25°C, 10°C and 45°C. In addition, a three-dimensional thermal model has been developed within the frame of open source computational fluid dynamics (CFD) to analyze the thermal behavior of lithium-ion batteries (LiBs). Thermal evolutions of the cells during the profile are recorded to witness the temperature distribution and the validation of the model. The model has indeed well captured the evolution process of the cells from electrical and thermal point-of-views and achieved reasonably good agreement with the measurements. For example, LTO-based cells have shown an interesting behavior for which the battery was able to undergo a fast-charge at any tested temperature and the temperature still remained stable (a temperature rise of less than a 3°C). These parametric studies demonstrate that the model methodology can be used to predict LiB temperature distribution under fast-charging profiles.

Lithium-Ion Capacitor: Analysis of Thermal Behavior and Development of Three-Dimensional Thermal Model

The large push for more environmental energy storage solutions for the automotive industry by different actors has led to the usage of lithium-ion capacitors (LICs) combining the features of both lithium-ion batteries (LIBs) and electric-double layer capacitors (EDLCs). In this paper, the thermal behavior of two types of advanced LICs has been thoroughly studied and analyzed by developing a three-dimensional (3D) thermal model in COMSOL Multiphysics®. Such an extensive and accurate thermal 3D has not been fully addressed in literature, which is a key building block for designing battery packs with an adequate thermal management. After an extensive measurement campaign, the high accuracy of the developed model in this paper is proven for two types of LICs, the 3300 F and the 2300 F. An error between the simulation and measurements is maximum 2 °C. This 3D model has been developed to gain insight in the thermal behavior of LICs, which is necessary to develop a thermal management system, which can ensure the safe operation of LICs when used in modules or packs.

Thermal conductivity of Li-ion batteries and their electrode configurations – A novel combination of modelling and experimental approach

A bottom-up approach to calculate the overall and averaged thermal properties of the jelly roll or electrode stack of Li-ion cells in a generally applicable way is introduced. The model is based on temperature-dependent material properties and is specifically applied to a prismatic hardcase cell. The geometrical properties, such as width, depth, height, porosity, tortuosity, and the saturation with electrolyte are considered. Most of the material properties are determined by own measurements within a wide temperature range and compared with literature data. Anisotropic unit cell properties for homogenised three-dimensional thermal models and the corresponding representative thermal conductivity for one- or two-dimensional models can be calculated. A non-destructive measurement technique to determine the thermal conductivity of prismatic hardcase cell geometries and validate the described model is presented.

Heat source model for laser beam welding of steel-aluminum lap joints

In this study, a three-dimensional thermal conduction model based on the finite element analysis was established to predict a heat distribution during laser welding in overlap configuration of austenitic stainless steel 1.4301 and hardenable aluminum alloy 6016. A hybrid model based on two expanded curve-rotated volumetric heat sources is suggested to capture the complex weld geometry. Since thermal flow in the overlap area is a crucial part of the model, an analytic calculation of a thermal contact conductance between the plates and its subsequent implementation in the FE model through a superposition of two contact surfaces are described in details in this paper. Full thermal cycles, weld shapes, and thus mixing grades were successfully predicted by means of the developed model for different parameter combinations.

A multi-fidelity information fusion metamodeling assisted laser beam welding process parameter optimization approach

Selecting reasonable laser beam welding (LBW) process parameters is very helpful for obtaining a good welding bead profile and hence a high quality of the welding joint. Existing process parameter optimization approaches for LBW either based on cost-expensive physical experiments or low-fidelity (LF) computer simulations. This paper proposes a multi-fidelity (MF) metamodel based LBW process parameter optimization approach, in which different levels fidelity information, both from LF computer simulations and high-fidelity (HF) physical experiments can be integrated and fully exploited. In the proposed approach, a three-dimensional thermal finite element model is developed as the LF model, which is fitted with a LF metamodel firstly. Then, by taking the LF metamodel as a base model and scaling it using the HF physical experiments, a MF metamodel is constructed to approximate the relationships between the LBW process parameters and the bead profile. Two metrics are adopted to compare the prediction accuracy of the MF metamodel with the single-fidelity metamodels solely constructed with physical experiments or computer simulations. Results illustrate that the MF metamodel outperforms the single-fidelity metamodels both in global and local accuracy. Finally, the fast elitist non-dominated sorting genetic algorithm (NSGA-II) is used to facilitate LBW process parameter space exploration and multi-objective Pareto optima search. LBW verification experiments verify the effectiveness and reliability of the obtained optimal process parameters.

A Lumped Thermal Model Including Thermal Coupling and Thermal Boundary Conditions for High-Power IGBT Modules

Detailed thermal dynamics of high-power IGBT modules are important information for the reliability analysis and thermal design of power electronic systems. However, the existing thermal models have their limits to correctly predict these complicated thermal behavior in the IGBTs: The typically used thermal model based on one-dimensional RC lumps have limits to provide temperature distributions inside the device; moreover, some variable factors in the real-field applications like the cooling and heating conditions of the converter cannot be adapted. On the other hand, the more advanced three-dimensional (3-D) thermal models based on finite-element method (FEM) need massive computations, which make the long-term thermal dynamics difficult to calculate. In this paper, a new lumped 3-D thermal model is proposed, which can be easily characterized from FEM simulations and can acquire the critical thermal distribution under long-term studies. Meanwhile, the boundary conditions for the thermal analysis are modeled and included, which can be adapted to different real-field applications of power electronic converters. Finally, the accuracy of the proposed thermal model is verified by FEM simulations and experimental results show a good agreement.

Study on the criticality of thermal safety of cylindrical battery

In view of the complexity of the storage environment in the process of storage and transportation, typical storage environment of cylindrical battery was analyzed in this paper. The corresponding three-dimensional thermal explosion models were established which considering non-uniform heat dissipation of the lateral surface and different heat dissipation of top and bottom surfaces. Based on the seven-point difference method and Newton–homotopy method, calculation algorithm and program of partial differential equation group have been established and verified. The influence of H and Biot on the criticality of system was analyzed. The results of a kind of cylindrical battery which stored in two typical environments (shelf and ground) were obtained by the calculation program. The critical thermal explosion ambient temperature of cylindrical battery is, respectively, 568.0 and 566.6 K. When the ambient temperature is 575 K, the thermal explosion time to ignition is, respectively, 1.504 (5194.7 s) and 1.596 (5512.1 s).

Machined surface temperature in hard turning

Abstract Machined surface temperature is critical in turning of hardened steels because high surface temperature can lead to the formation of the white layer, which may have negative impacts on the steel fatigue life. This paper presents two experimental methods to measure machined surface temperatures in hard turning. The first method, based on a tool-foil thermocouple, estimates the machined surface temperature using a metal foil embedded in the workpiece to measure the tool tip temperature. The second method uses a thermocouple embedded in the tool with its tip continuously sliding on the machined surface behind the cutting edge during hard turning. A three-dimensional thermal model is developed and the inverse heat transfer method is applied to find the machined surface temperature near the cutting edge. For validation, hard turning tests were conducted and the cutting forces, tool-foil voltages and embedded thermocouple voltages were measured simultaneously at three levels of feed rates. The peak machined surface temperature occurred along the intersection of cutting edge and the machined surface. Its magnitude was mainly determined by the shear plane heat source and further increased due to flank face frictional heat source. Measurement results showed comparable predictions between the two developed methods with an average deviation of 30 °C over the 500–800 °C range. These two methods, although based on very different approaches, have both proven feasible for the measurement of hard turning machined surface temperatures.

Perforated cellular wooden slabs under fire: Numerical and experimental approaches

This work presents a numerical and experimental approach in order to predict the fire resistance of perforated cellular wooden slabs. The wooden slabs are lightweight, easy installation, excellent architectural, thermal and acoustic characteristics. However, its high vulnerability to fire, requires their behaviour assessed accurately. Wood material produces a surrounding char layer in depth, when exposed to fire resulting in a reduced residual section. For this purpose, different cellular wooden slabs, with the bottom surface perforated, including different small and large rectangles and circles, were tested and submitted to fire exposure. The experimental study was conducted in laboratory in accordance with European standard (EN1365-2, 2012), using a fire resistance furnace which complies the requirements of European standard (EN1363-1, 2012). Also a three-dimensional thermal and transient numerical model, using a finite element program Ansys®, was validated with experimental tests at real scale. The numerical and experimental results show good agreement. The numerical model can easily be adjusted for other constructive solutions, in order to facilitate fire safety tests, in buildings with wooden slabs used in floors or in ceilings applications.

Three dimensional material removal model of laser-induced backside wet etching of sapphire substrate with CuSO4 solutions

The mechanism of laser-induced backside wet etching (LIBWE) of sapphire substrate with CuSO4 solution is considered as a two-step process. First, it deposits the layer from copper sulfate solution on the backside of sapphire substrate by 1064nm laser irradiation. Then it is followed by the absorption of deposited layer to laser irradiation, resulting in the etching of the sapphire. Therefore, the material removal of LIBWE is based on laser interaction with multilayer materials (sapphire substrate--deposition layer--liquid solution). A three-dimensional thermal model is established to simulate the material removal during the LIBWE process by considering the material data variations of temperature, enthalpy change and latent heat fusion. The model can predict the groove shape influenced by the laser processing parameters (laser fluence, scanning velocity and scanning pass). The simulation results indicate that the groove depth increases with the decreasing of scanning velocity, the increasing of laser fluence and the scanning pass. The groove width is comparable with the focal beam diameter. Some peaks and valleys occur at the bottom of the groove. A comparison between the modeling and experiment indicates that the groove shape in simulation agrees well with the experiment data at laser pulse energy of 4.3mJ/pulse, scanning velocity of 15mm/s and the scanning pass of 4. i.e, the present physical model is effective and feasible.

Thermal safety of lithium-ion batteries with various cathode materials: A numerical study

Lithium-ion batteries for electrical vehicle and large-scale energy storage applications have developed significantly in recent years. However, the safety issue is still a major technical challenge and has become a key factor retarding further deployment of lithium-ion batteries. Numerous experimental studies on the thermal stability of cathode materials have been performed to seek safer battery materials. In this work, a three-dimensional thermal model describing oven abuse processes of lithium-ion batteries was established to study the thermal stability and thermal safety of cathode materials. Five various cathode materials (i.e. LiCoO2, LiNi0.8Co0.15Al0.05O2, Li1.1(Ni1/3Co1/3Mn1/3)0.9O2, LiMn2O4, and LiFePO4) were taken; their response to oven thermal abuse was simulated and discussed in detail. Simulation results show that the LiMn2O4 cell has the best thermal stability and the LiFePO4 cell has the best thermal safety of all the five various lithium-ion batteries. Effects of oven temperature on battery thermal behaviors during oven thermal abuses were particularly analyzed and the critical oven temperatures to trigger thermal runaway were obtained for these batteries as well.

Thermal model and temperature field in rail grinding process based on a moving heat source

A three-dimensional thermal model that the grinding wheels are simplified as a moving heat source in the rail grinding process was established and used to explore the effect of grinding parameters on the temperature field of ground rail. The results indicate that the highest temperature of ground rail increases with an increase in the grinding power. The increase of grinding surface width and moving velocity causes a fall of ground rail temperature. It should be noted that the temperature of ground rail would continue to rise when the first car with 12 grinding wheels passes through the rail surface. However, the temperature does not increase when the second car passes through. Compared with distributing on the same grinding surfaces, two grinding wheels distributing on two adjacent grinding surfaces would lower grinding rail temperature. The results are beneficial to improve the reasonable arrangement of grinding wheels in the rail grinding process.

Optimization of laser welding process parameters of stainless steel 316L using FEM, Kriging and NSGA-II

Laser welding process parameters have significant effects on the welding bead profile and quality of the welding joint. This paper proposes an integration method of process parameters optimization using finite element method (FEM), Kriging metamodels and nondominated sorting genetic algorithm II (NSGA-II) in laser welding for stainless steel 316L. The process parameters in this study are laser power (LP), welding speed (WS) and laser focal position (LF). Firstly, a three-dimensional thermal finite element model is developed to obtain the simulated results of bead width (BW) and depth of penetration (DP). Then, Kriging metamodels are constructed to reflect the relationship between input process parameters and output responses. Finally, NSGA-II is used to search for multi-objective Pareto optimal solutions. In addition, the main effects and contribution rates of multiple process parameters on welding bead profile are analyzed. The results of verification experiments indicate that the optimal process parameters are effective and reliable for producing expected welding bead profile.

Two-Dimensional Thermal Model of Lithium Ion Battery Cell Based on Electrothermal Impedance Spectroscopy

Lithium ion (li-ion) batteries are gradually increasing their volumetric power and energy densities due to requirements imposed by electric vehicles and portable electronics applications. In consequence, modern lithium ion battery cells and battery packs are having much more compact design where a high amount of energy is encapsulated in a small volume. This imposes a need for an accurate thermal modeling of li-ion batteries in order to avoid battery cells overheating, which leads to safety concerns (e.g. thermal runaways) and accelerates battery cell's performance degradation. Conventional methods for two- and three-dimensional thermal modeling of lithium ion batteries, usually require a coupled electrochemical battery cell model and a lot of knowledge about battery cell internal composition which are not provided and often protected by the battery cell’s manufacturers. This paper proposes an alternative method for battery cell 2D modeling based on the extended concept of electrothermal impedance spectroscopy. Moreover, a verification of the accuracy of the obtained results will be performed. Electrothermal impedance spectroscopy and proposed approach Barsoukov et al. were the first ones presenting the concept of electrothermal impedance spectroscopy (ETIS) in [1]. Later the concept was further extended and improved by Schmidt et al., by introducing internal heat excitation and a more accurate frequency-based measurement method [2]. ETIS is a non-destructive, relatively easy to implement, ‘entropy-free’ and not requiring any a priori knowledge about cell internal composition method, which is used for determining battery cell’s heat capacity and heat conductivity. The ETIS method is based on applying a specific heat flow to the battery and measuring the amplitude and phase delay of resulting battery temperature response [2]. For the frequency-based method, this procedure is repeated for several heat excitation frequencies and thus the thermal impedance function is defined. So far, the ETIS method has been used for one point measurements. This work is extendig the ETIS concept to multi-point measurements and study the accuracy of the two-dimensional thermal model parameterized by the means of the multi-point ETIS measurement. Laboratory setup and description of experiments A laboratory setup was built based on a high-bandwidth Kepco galvanostat and several high-precision temperature sensors located at different points of the high-power LiMO2/Li4Ti5O12 battery cell (Fig.1). Frequency-based method with internal heat generation was applied and results for two spots, on the battery cell surface, are presented in Fig.2. The obtained results are demonstrating different ‘local’ thermal impedances of the battery cell and in consequence uneven battery cell heating (Fig.3 ad Fig.4). These spot dependent thermal impedance functions can be used later for two-dimensional thermal modeling of battery cell by means e.g. Cauer model [3]. Final version of the paper In the final version of the paper, the detailed results from multi-point ETIS will be presented and discussed. A two-dimensional equivalent thermal circuit based battery model will be developed and parametrized by means of multi-point ETIS. Finally, the accuracy of this two-dimensional battery thermal model [3], developed based on the multi-point ETIS, will be analyzed.

Thermal Stress and High Temperature Effects on Power Devices in a Fault-Resilient NPC IGCT-Based Converter

The integrated gate-commutated thyristor and presspack power diodes have been successfully applied in medium-voltage neutral point-clamped converters in the power range from hundreds of kilowatt to tenths of megawatt. Responsible for driving key processes in the industry, high reliability and availability are crucial for these converters, since their repair or replacement after failure events may take too long. Given the vital importance of such equipment for the drive systems, they are equipped with protection schemes that are usually reliable, but not infallible. If the protection scheme of the converter does not work properly in a short-circuit situation, serious damages may be expected on its power semiconductor devices. In this paper, the power semiconductors thermal behavior is investigated using finite-element models in the COMSOL Multiphysics software. Three-dimensional thermal models of the power devices were raised by industrial radiography techniques, aiming to expand the information provided by the manufacturers. The authors show how these results can be used in a real equipment to attenuate the catastrophic effects of the protection scheme malfunction, so limiting the damage pattern within the converter to their least complex power devices.

RETRACTED: A pure thermal model to evaluate heat-affected zone when milling E-glass fiber-reinforced polyester composites

This paper aims at investigating the resistance-to-vitrification of glass fiber-reinforced plastics when milling. A three-dimensional thermal model using volumetric heat source with Gaussian distributed cylindrical flux was developed as DFLUX subroutine and implemented into Abaqus/Standard code. The wheel feed was simulated by the source motion at 250 mm min−1 with spindle speeds of 11,460, 15,280, and 19,100 rpm. Milling tests using abrasive wheel with 10 mm in diameter were conducted on the composite specimens of dimensions 100 × 25 × 4 mm3 with fibers oriented both parallel and perpendicular to the milling direction. Four equidistant thermocouples were embedded within the medium plane of the specimen in order to measure the temperature histories. Each series of tests was repeated four times under identical conditions. Predictions confronted to measurements demonstrated the validity of the proposed model. Cutting perpendicular to fibers was found favoring in-depth heat dissipation. However, the fibers a...