Heat Generation Distribution Research Articles

Review of Li- Ion Battery Thermal Management Methods and Mitigating Techniques: 2/3 W Electric Vehicle for Tropical Climatic Condition

The quantum of transient heat generated and subsequent transient temperature is interdependent non linear functionality with several boundary conditions affecting the lithium ion battery pack performance with transient heat conduction under tangible operating and ambient temperature has a substantial short and long term impact on the electrical performance, life, reliability and safety of lithium-ion batteries. In the tropical condition, the variation in ambient temperature of lithium ion battery pack for 2/3 wheeler is comparatively high and varies from + 25oC to +55oC because of higher atmospheric temperature as well as the batteries having less thermal evacuation system and ventilation because of lack of space and other constraints, thus exerting constantly higher but variable thermal stress like temperature gradients, thermal expansion or contraction and thermal shocks causes irreparable aging and degradation effect. It is essential to quantify the transient heat generation and temperature distribution of a battery cell, module, and pack during different operating conditions with methodologies for its proficient management and mitigating techniques. The demand for thermal management is multi prong to maintain the temperature of batteries within the safe operating temperature range zone and the non-uniform temperature distribution must remain within the range of the reference limit for the purpose of preventing the occurring of thermal runaway for favorable working performance. The objective of thermal management is to device suitable monitoring and measurement, designing the suitable thermal path to expel heat generated and suitable mechanism for prevention of breakdown. In this paper, the comparative transient temperature distributions across two identical battery packs(48V24Ah (15S4P) series parallel connected lithium-ion Ferro phosphate cell), one without any thermal management system and other with thermal management system are studied under various charging and discharging currents with various ambient temperature range, similar to tropical region for checking the effectiveness of designed thermal management system of the battery pack

A Simplified Single-Layer Pseudo-4D Electrochemical/Thermal Model for Large-Format Li-Ion Pouch Cells

Ever since the first commercial Li-ion battery launched in 1991, Li-ion batteries have been the best available energy storage systems for consumer electronics [1]. With recent advances in cell capacity, cycle time and battery management systems, they have become even more popular as an ideal candidate for grid-scale energy storage and electric vehicles [2].When a battery is being charged or discharged, there is inevitable heat generation due to electrochemical reactions, ohmic resistance and entropy changes [3]. If the amount of heat generated is not sufficiently dissipated from the battery, it could substantially increase the cell temperature which leads to severe cell degradation and even catastrophic thermal runaway. Furthermore, large temperature inhomogeneity is commonly observed in large-format pouch cells due to the non-uniform local current density and reaction rate. Therefore, in order to maintain stable and durable performance, it is vital to understand the irregular heat generation and temperature distribution associated with cell geometry and properties, and design appropriate cooling techniques accordingly.Battery modeling is a useful tool to investigate the electrochemical reactions and consequent heat generation during charging and discharging. An experimentally validated battery model has the ability to accurately predict the cell response under different test conditions, eliminating the need for repeated lengthy experiments. Among all the existing Li-ion battery models, the pseudo-2D (P2D) model, originally proposed by John Newman and his students [4-6], is the most widely accepted electrochemical model for Li-ion batteries. Based on this, a few battery thermal models have been established by coupling a P2D electrochemical model with a 3D heat transfer model [7-9]. The electric and concentration fields are solved in a 1D unit-cell and are extracted to calculate the heat generation rates in a 3D battery geometry. However, such a method would introduce large errors in large-format pouch cells as the assumption of uniform current density and reaction rate is not valid.Therefore, in this study, we would like to propose a pseudo-4D (P4D) battery model, which extends the original P2D model from 1D to 3D battery geometry. The charge balance, mass balance and reaction kinetics, as well as energy balance, are spatially resolved for the entire battery geometry, considering the inhomogeneity of battery state properties. Furthermore, a scaling analysis is carried out via non-dimensionalization of the model equations to demonstrate that a single-layer cell would be sufficient to simulate the overall electrical and thermal performance of the battery which actually contains multiple cell layers. The complexity of the model can thereby be reduced to make the model more time-efficient.

Effect of Plate Curvature on Heat Source Distribution in Induction Line Heating for Plate Forming

Line heating is an essential process in the formation of ship hull plates with a complex curvature. Electromagnetic induction heating is widely used in the line heating process. In electromagnetic induction heating, the shape of the coil and the air gap between the inductor and workpiece could influence the heat source distribution. Moreover, in the line heating process, the change of curvature of the plate will cause a change of the air gap of the inductor. Magnetic thermal coupling calculation is an effective method for simulating induction heating. This paper used the finite element method to calculate the distribution of heat sources in different initial plate curvatures and coil widths. The changes in heat source distribution and its laws were investigated. The results show that when the coil width is less than 100 mm, the effect of plate curvature on heat source distribution and strain distribution is not apparent; when the coil width is greater than 100 mm, the plate curvature has a visible effect on the heat generation distribution. In the case of a curvature increasing from 0 to 1 and a coil width equal to 220 mm, the Joule heat generation in the center of the heating area is reduced by up to 21%.

Improved T MAX Estimation in GaN HEMTs Using an Equivalent Hot Point Approximation

In this article, heat generation distribution and maximum device temperature of gallium-nitride (GaN) high-electron-mobility transistors (HEMTs) are investigated by using the 2-D electrothermal and finite-element method (FEM) simulations. Devices with different gate lengths and source-to-drain spacing are investigated. It is observed that the maximum device temperature ( ${T}_{{\text {MAX}}}$ ) depends on the drain-to-source spacing and is almost independent of the gate length and that the assumption of a uniform heat generation region, under the gate, is not accurate; this is contrary to conventional calculation methods. Moreover, based on the results, a new approximation is proposed to use in the FEM simulations that can estimate ${T}_{{\text {MAX}}}$ more accurately. This method does not require physics-based technology computer-aided design (TCAD) simulations and can work with a low mesh density. The performance is compared with prior methods.

Impact of Geometry, Doping, Temperature, and Boundary Conductivity on Thermal Characteristics of 14-nm Bulk and SOI FinFETs

In this paper, the self-heating effect (SHE) in 14-nm bulk and SOI FinFETs are investigated through the TCAD simulation. To achieve high authoritative evidences, the calibration is performed by ${I} _{\mathrm{ D}}$ - ${V} _{\mathrm{ G}}$ curve fitting based on the experimental data. The main contributions include: 1) The distribution of heat generation and temperature gradient along the channel are disclosed. Two peeks of heat generation are observed in source extension (SE) and drain extension (DE), respectively; 2) The dependence of maximum lattice temperature and thermal resistance on device geometry and parameters including fin width, fin height, length of SE and DE, the thickness of STI and BOX, doping concentration of extension, and gate voltage, are thoroughly analyzed; 3) The influence of SHEs on the electrical characteristic of FinFET under different ambient temperatures are also revealed. Moreover, the critical heat removal paths of bulk and SOI FinFETs are discussed. For the former, most of heat vertically diffuses to the substrate, and then to heat sink, whereas in SOI FinFET it firstly dissipates to source, drain, and gate, and then to heat sink. Finally, several optimization thumbs of SHEs are proposed.

Numerical simulation of 3D electromagnetic–thermal phenomena in an induction heated slab

A mathematical model was developed to get an insight into 3D electromagnetic–thermal phenomena in an induction heated steel slab with a large width/thickness ratio by solving a fully coupled Maxwell equations and energy conservation equation. The spatial heat radiation between the slab surface and the refractory wall in an induction furnace was considered. The electromagnetic induction and temperature distribution features inside the slab with time evolution were described. The effects of electromagnetic induction parameters, thermal conductivity of the material and process parameters on the induction heating process were theoretically examined. Numerical results show that the spatial distribution of induction heat generation inside the slab is non-uniform. The high work frequency and the low heat conductivity of slab increase the non-uniformity of slab induction heating process. The radiative heat loss and heat transfer between the slab and the metal parts used for holding the slab have an important effect on the slab surface temperature. It is necessary to separately control the current input in the multi-layer coil windings along the height direction of furnace and adopt the multi-step heating strategies with time evolution to improve the homogenization of the slab temperature.

Effect of track irregularities of high-speed railways on the thermal characteristics of the traction motor bearing

The operating temperature plays a key role in the service reliability of ball bearings used in the traction motor of high-speed trains. Studies on the heat generation and temperature distributions of the bearing under the vehicle vibration environment are critical for designing the high-speed train traction motor bearing and to monitor its operation. In this paper, an SKF friction torque model that considers the inlet shear heating reduction and kinematic replenishment/starvation reduction was used to calculate the power loss of the bearing operating in a high-speed train. A thermal analysis model of the bearing, which takes into account the vehicle vibration due to track irregularities, was developed to study the thermal characteristics of the bearing operating in a high-speed train. Experiments were conducted on a service high-speed train (i.e. CRH380B) to validate the proposed bearing thermal analysis model. The thermal characteristics of the bearing and the influence of key factors on the operating temperature of the bearing under vehicle vibration due to track irregularities were studied with the proposed bearing thermal analysis model. The results show that the thermal failure of the bearing subassemblies most likely occurs at the balls region owing to the highest temperature in that region, compared to the inner and outer raceway of the bearing. The method of applying grease with appropriate kinematic viscosity should be adopted to reduce the power loss of bearing while meeting the lubrication requirement. The vehicle vibration due to track irregularities significantly influences the thermal characteristics of high-speed train motor bearings, which cannot be ignored in the thermal analysis of bearings operating in a high-speed train.

Novel Mesoscale Electrothermal Modeling for Lithium-Ion Batteries

This paper devises an innovative mesoscale electrothermal model for Li-ion batteries. This model manipulates the mesoscale calculation grid in finite element analysis as independent small cell sandwiches and establishes a lumped equivalent circuit model for each cell sandwich. Then, such electrical models are arranged in parallel to form a multilayer equivalent circuit to simulate electrical characteristics of a whole battery, through capturing the current and terminal voltage of each constituent cell sandwich. This modeling idea overcomes the entrenched disadvantage of heat generation models with lumped parameters, i.e., the unavailability of heat generation distribution inside a battery. Besides the current and terminal voltage, the temperature and state of charge dependent open-circuit voltage and entropy coefficient are incorporated into a Newman's heat generation model to estimate the heat generated in the calculation grid. The battery temperature distribution is eventually derived by solving the heat conduction equation with thermal conductivity as a function of the battery temperature. We leverage the developed electrothermal model to track the temperature evolution of an 18 650 Li-ion battery at different ambient temperatures and discharge rates, for the first time. Experimental results demonstrate that the electrothermal model can precisely emulate the battery thermal dynamics with an average error of 0.72 °C. Moreover, a comparative study shows that the proposed model outperforms common resistance-based thermal models that do not consider the heat generation distribution and the interdependence between the battery temperature and thermal conductivity.

Numerical investigations of effect of input process parameters on heat generation in friction stir welding

This article investigates the effect of input process parameters on the heat generation in friction stir welding (FSW) using numerical techniques. The computational fluid dynamics (CFD) based numerical modeling technique is used to predict the heat generation, temperature distributions with consideration of tool pin profile, tool rotation speed and welding speed. To investigate the effect input process parameters on heat generation and temperature distribution, four different tool pin profile are used namely cylindrical, conical, cylindrical-conical and stepped-conical pin profile. The geometric modeling and numerical simulation is carried out using ANSYS Fluent software. The peak temperature produced by tool pin profile is used to predict the effect of input process parameter on the heat generation. The simulation results show that the peak temperature value directly proportional to the tool rotation speed. The magnitude of peak temperature produced by stepped-conical pin profile tool is highest among the all tool pin profile peak temperature along the thickness. The effect of tool rotation speed on peak temperature is highly significant but welding speed effect on peak temperature is insignificant for all tool pin profile at particular tool rotation speed along the thickness of the work piece.

Transient Temperature Distributions on Lithium-Ion Polymer SLI Battery

Lithium-ion polymer batteries currently are the most popular vehicle onboard electric energy storage systems ranging from the 12 V/24 V starting, lighting, and ignition (SLI) battery to the high-voltage traction battery pack in hybrid and electric vehicles. The operating temperature has a significant impact on the performance, safety, and cycle lifetime of lithium-ion batteries. It is essential to quantify the heat generation and temperature distribution of a battery cell, module, and pack during different operating conditions. In this paper, the transient temperature distributions across a battery module consisting of four series-connected lithium-ion polymer battery cells are measured under various charging and discharging currents. A battery thermal model, correlated with the experimental data, is built in the module-level in the ANSYS/Fluent platform. This validated module thermal model is then extended to a pack thermal model which contains four parallel-connected modules. The temperature distributions on the battery pack model are simulated under 40 A, 60 A, and 80 A constant discharge currents. An air-cool thermal management system is integrated with the battery pack model to ensure the operating temperature and temperature gradient within the optimal range. This paper could provide thermal management design guideline for the lithium-ion polymer battery pack.

Experimentally Determined Material Parameters for Temperature Prediction of an Automobile Tire using Finite Element Analysis

The material parameters of an automotive truck tire were experimentally determined and validated for use in a thermal finite element analysis to determine the temperature distribution in the tire due to different operating conditions. Uni-axial tensile tests were performed on tire samples. The force displacement response of each was used to determine material properties by means of direct curve-fitting and iterative numerical procedures. Equivalent finite element simulation models were used to validate the properties. Hysteresis behaviour of the rubber regions were identified by dynamic mechanical analysis. Material definitions were incorporated into a finite element model to predict the steady-state heat generation and temperature distribution within a tire due to hysteresis. Experimental rolling tire temperature measurements were taken on a test bench. A comparison of the results with those obtained from the equivalent thermal models was used to validate the numerical models.

Thermo-mechanical simulation using microstructure-based modeling of friction stir spot welded AA 6061-T6

An innovative analysis methodology integrated microstructure-based modeling and thermo-mechanical coupling simulation was developed to analyze processing thermal history and then attain simulated mechanical properties of FSSW joint with a higher accuracy. Such numerical evaluation model with measured geometry, hook defect as precast cracks and modified material properties as well as attached thermal residual stress was validated to mainly cover mechanical results produced by processing course. A series of thermal simulation settings which approached actual manufacturing conditions were applied, considering a moving heat source model coupled with Gauss surface and double ellipsoidal body, axial welding force, TCC varied with pressure at the steel-Al contact interface and preheating temperature field of the tool. So then the variations of heat generation, interfacial pressure, temperature field and residual stress distribution were numerically calculated. Finally, tensile fracture simulation of the established joint model was performed to test the simulated accuracy in mechanical performance using this method. The mechanical evolution mechanism to failure was also unveiled. Moreover, the cut-off temperature to achieve improved material properties in SZ and TMAZ was found to be about 375 degrees. The regulation mechanism of such solid phase welding was inferred to be the negative feedback of temperature by means of the decreasing yield stress with increasing temperature. The predicted thermal cycle, geometries of several metallurgical zones, fracture mode and load bearing characteristics were all in good agreement with the experimentally measured ones, validating the reliability of this proposed approach.

ON–OFF: a reactive routing algorithm for dynamic thermal management in 3D NoCs

Dynamic thermal management (DTM) techniques of three-dimensional (3D) Network-on-Chips (NoCs) are employed to rescue the chip from thermal difficulties. Reactive routing algorithms, which utilise router throttling technique as a popular DTM, disregard distribution of heat generation of routers resulting in more throttled routers as well as long packet delays in throttled processing elements. This study proposes a reactive routing algorithm for 3D NoCs to (i) dynamically detour packets from hot zones containing throttled routers and (ii) minimise the number of required router throttling in the network. The proposed routing algorithm defines two virtual networks to enhance the path diversity for packets in each layer of 3D NoCs. The selection of diverse paths distributes heat generation to alleviate the thermal variance. The proposed routing algorithm is analysed by turn model to achieve deadlock freedom. Access Noxim simulator is also used to evaluate the performance and the thermal behaviour of the proposed routing algorithm in the variety of conditions. Results show that the proposed routing algorithm improves temperature variance by 9-39% and reduces number of throttled routers by 16-86%, which is achieved at the cost of one extra virtual channel per each physical channel in the XY -plane.

Temperature distribution of T- joint friction stir welding

Friction stir welding is a reliable welding method; it can be employed to join different structural configurations. Joint types such as lap, butt and T have been successfully produced by this welding method. In this study, a trial has been made to numerically simulate the heat generation and temperature distribution during the welding process of a T-joint. The workpieces materials were hardened 5052 and tempered 7075 Al Alloys, each material was investigated separately. Different rotational and welding speeds were used, besides, the pin length was also varied to accommodate the investigation of the top plate thickness effect. A visco-plastic finite element model was adopted to investigate the effect of parameters ranges on the temperature distribution. The results showed that the temperature distribution of T-joint depends mainly on the material to be welded and rotational speed. Besides, increasing the pin length from 7 to 10 mm could significantly increase the resulted temperature by approximately 14%. Therefore, the thickness of the upper plates of the T-joint plays a significant role on the resulted process temperature.

A Review on Ohmic Heating Technology: Principle, Applications and Scope

Ohmic heating is a novel and alternating thermal processing technology wherein food materials are heated by passing electric current through materials. Ohmic heating has extreme potential for achieving rapid and uniform heating in foods, providing microbiologically safe and high quality foods. Ohmic heating presents a wide range of potential applications including pasteurization, sterilization, aseptic processing, cooking, thawing, blanching, evaporation, extraction, fermentation, and in the military field or long-duration space missions. This review discusses the brief history, basic principle, some process parameters, applicable food products, potential commercial applications and current industrial status of ohmic heating in food industry throughout the world. The review also highlights the scope and work done on ohmic heating in India. The corrosion problems in electrodes and heterogeneous heat generation rate and distribution are interesting area for further research. Ohmic heating is a good comparable with the other ideal technologies like microwave heating, radio-frequency heating and induction heating. More and intensive investigations are required to assess performance and to reduce the overall cost of ohmic heating for viability of commercial application of this technology also in developing countries like India.

The distribution of frictional heat generated between the contacting surfaces of the friction clutch system

The frictional heat generated during the initial engagement will influence negatively the performance and lifetime of the friction clutches, this heat generated will lead to appear excessive temperatures in the contact surfaces and subsequently accelerate the wear process in the contact area. The amount and distribution of the heat generated are depending on many variables such as the contact pressure, the coefficient of friction, sliding speed, etc. In this research paper, MATLAB program was built based on the analytical solutions which used to determine the distribution and amount of the total heat generation at the interface between the contacting parts of the friction clutch. Furthermore, the amount and distribution of the frictional heat generation on the contact area of each element of the friction clutch system (flywheel, clutch disc, and pressure plate) during the sliding stage was calculated. Finally, the program was introduced using MATLAB GUI (graphical user interfaces) to analyze the heat generated on the friction clutch surfaces. Different types of materials (thermal properties), sliding time, torque function and angular sliding speed function can be applied into the software to find the solution for a specific case of a single-plate friction clutch.

Investigation on lithium-ion battery electrochemical and thermal characteristic based on electrochemical-thermal coupled model

A lithium-ion battery consists of numerous electrochemical cell units, and is treated as an assembly of one dimensional (1D) cell unit connected in parallel. The electrochemical and thermal characteristics of 1D cell unit have a great influence on battery performance. The thermal behavior and the dynamic evolution of electrochemical reaction in the cell are simulated. At lower discharge rate, reversible heat dominates the heat generation, but the proportion of irreversible heat gradually increases with the discharge rate. Non-uniform distribution of heat generation and electrochemical reaction rate in the cell increase with the discharge rate. Temperature has little effect on average heat generation rate and mainly influences the distribution uniformity of electrochemical reaction rate and heat generation in the cell. The temperature distribution in a battery is researched based on multi-cell 1D model. It is found that temperature in the battery presents a parabolic distribution in the laminated direction and the temperature gradient significantly increases with the cells number, which is mainly induced from the lower heat conductivity in the laminated direction. The bulk temperature will be decreased and safety of battery will be improved with the increase of cooling strength, but the temperature difference within the battery will be significant increased simultaneously. The number of cell can’t exceed 80 for a monomer battery with this electrode thickness and an active battery thermal management system (such as forced air cooling and liquid cooling system) is also indispensable to keep the temperature difference and surface temperature in the reasonable range at 5C discharge rate. At the same time, the thickness of the battery need to be chosen based on the application.

Coupled Electro-Thermo-Mechanical Simulation for Multiple Pellet Fabrication Using Spark Plasma Sintering

A coordinated experimental and computational analysis was undertaken to investigate the temperature field, heat generation, and stress distribution within a spark plasma sintering (SPS) tooling-specimen system during single- and multipellet fabrication of uranium dioxide (UO2) fuel pellets. Different SPS tool assembly configurations consisting of spacers, punches, pellets, and a die with single or multiple cavities were analyzed using ANSYS finite element (FE) software with coupled electro-thermo-mechanical modeling approach. For single-pellet manufacture, the importance of the die dimensions in relation to punch length and their influence on temperature distribution in the pellet were analyzed. The analysis was then extended to propose methods for reducing the overall power consumption of the SPS fabrication process by optimizing the dimensions and configurations of tooling for simultaneous sintering of multiple pellets in each processing cycle. For double-pellet manufacture, the effect of the center punch length (that separates the two pellets) on the temperature distribution in the pellets was investigated. Finally, for the multiple pellet fabrication, the optimum spacing between the pellets as well as the distance between the die cavities and the outer surface of the die wall were determined. A good agreement between the experimental data on the die surface temperature and FE model results was obtained. The current analysis may be utilized for further optimization of advanced tooling concepts to control temperature distribution and obtain uniform microstructure in fuel pellets in large-scale manufacturing using SPS process.

Broadband infrared absorbers with stacked double chromium ring resonators

A broadband absorber in the infrared wavelength range from 1 μm up to 5 μm is designed and demonstrated with stacked double chromium ring resonators on a reflective chromium mirror. The near-perfect broadband absorption is realized by combining the multilayer impedance match in the short wavelength range and the double plasmonic resonances in the long wavelength range, which is illustrated with an equivalent circuit model for the impedance analysis. The broadband absorber is proved to be angle-insensitive and polarization-independent due to the geometrical symmetry. The thermal analysis for heat generation and temperature distributions inside the absorber structure is also investigated.

Steady state and transient analytical modeling of non-uniform convective cooling of a microprocessor chip due to jet impingement

Heat removal from microprocessor chips with multiple regions of dynamic heat generation remains a critical technological challenge. Excessive temperature rise is undesirable for performance as well as reliability. Jet impingement cooling has been widely investigated as a potential thermal management technique due to the capability of localized cooling and of dynamically following the heat generation distribution. A jet offers large local convective heat transfer coefficient, for which theoretical models and correlations have been proposed for a variety of scenarios. However, not much work exists on using this information to determine the resulting temperature distribution. This paper addresses this need by developing analytical steady state and transient heat transfer models that account for the spatial variation in convective heat transfer coefficient and for spatially non-uniform heat flux. The solution is derived in the form of an infinite series, the coefficients of which are determined by solving a set of algebraic equations. Temperature rise predicted by the models are found to be in excellent agreement with finite-element simulations, while offering faster computation time and easier integration with design and performance optimization tools used in microelectronics. The analytical model is used for predicting temperature rise in a variety of scenarios to examine interesting optimization problems such as the cooling of multiple hotspots with a single jet, determining the optimal location of a jet, etc. Results presented here may facilitate improved thermal design and real-time performance optimization of microprocessor chips.