Thermal-electrical Model Research Articles

Vertical z-axis discontinuous carbon fibers for improved lightning strike performance of continuous fiber-reinforced polymer composites

Effective lightning strike protection for critical aerospace and wind applications requires high electrical conductivity to dissipate current efficiently. However, polymer matrix composites face a challenge due to their inherently insulating nature. While conventional carbon fiber-reinforced composites (CFRP) exhibit electrical conductivity in the planar direction, achieving through-thickness conductivity remains an ongoing challenge. In this work, we have undertaken the fabrication of CFRP interleaved with vertically oriented carbon fibers (Z-fiber) to impart higher electrical conductivity along the thickness direction. Two Z-fiber composite variations are prepared: Z-1 with a single layer of Z-fiber and Z-5 with five interleaved layers and compared with no Z-fiber layer (Z-0) composite. The composite panels were subjected to lab-scale lightning strike tests with a current magnitude of 100 kA. To emulate real-world service conditions, an aerospace-grade paint coating was applied to the composite laminates. Comparative analysis shows Z-1 reduces damage diameter to ∼22 mm compared to Z-0 (∼26 mm), while Z-5 exhibits the least damage (∼16.7 mm), confirmed by optical microscopy. Z-5 demonstrates nine times higher through-thickness electrical conductivity than Z-0, reducing electrical anisotropy substantially. Thermal-electric finite element damage modeling predicts surface damage within 6% of experimental values for both Z-0 and Z-5 composites. Flexural tests post-lightning reveal Z-5 retains 66% flexural strength and 86% modulus, significantly better than Z-0, which retains less than 40% for both properties. This study highlights the efficacy of Z-fiber composites in lightning strike protection, offering improved through-thickness conductivity and mechanical property retention.

Comparative study on the impact of different E-J relations on the performance of resistive superconducting fault current limiters under high and low impedance faults in cryo-electric aircraft

To achieve the goal of zero emission in aviation, it is critical to advance electric aircraft technologies, especially in short to medium range flights. Superconducting fault current limiters (SFCLs) have shown promising potential in electric aircraft system as a protection solution to limit the peak of fault current. Many research works focused on the SFCL performance under low impedance faults, where the fault current is much higher than the nominal current and the SFCL will transit to normal (metal) state quickly. However, there are limited reports on investigating the SFCL reacting to high impedance faults for electric aircraft system, where the SFCL does not abruptly transit to normal state. In this paper, we built an electric-thermal coupled model in MATLAB which simulates the behaviour of a resistive type SFCL both under low and high impedance faults. We investigated three mathematical relations of local electric field E and local current density J representing the transition from superconducting state to normal state, both under high and low impedance fault. The three mathematical relations are classic E-J power-law, modified E-J power-law and two- stage E-J power law. The electric-thermal model of the SFCL incorporating all these three types of mathematical relations, respectively, have been used to calculate the SFCL responses under high and low impedance faults, and compared with each other, as well as testing results. The limited fault current, voltage drop, resistance and temperature variations in the SFCL are observed and analysed. The results have shown that the proposed SFCL model is able to accurately characterise a resistive type SFCL under both high impedance and low impedance fault.

Energy optimization algorithms for multi-residential buildings: A model predictive control application

This study presents an optimization algorithm for Model Predictive Control (MPC) of the HVAC systems in multi-family residential buildings assessing the performance of four objective functions. Implemented in C++, using the free OR-Tools optimization library, the model is formulated a Mixed Integer-Linear Programming (MILP) problem. The study analyses the results of tests conducted on a 20-dwelling block in Switzerland across various weather and occupancy conditions, resulting in a parametric study of 64 cases.The models developed for the MPC are Grey-box type for the interconnected energy systems: the building, thermal storage tanks, a heat pump, the ventilation system and PV collectors, highlighting a radiant wall heating system integrated into the building facade. The tanks and the heat pump models were informed with manufacturer data, while for the building a R3C3 thermal-electrical equivalent model was developed, calibrated using TRNSYS simulations with a root mean square error of 1.7%.Findings demonstrate how the algorithm optimizes the operation according to the desired criteria, while ensuring indoor comfort with a 15-minute time resolution. The time execution of the majority of cases is under 3 min in a low-specs computer, affirming its practical viability for real-world implementation.

Experimental and numerical simulation studies of electrical resistance of cementitious materials under varying temperature history

Many in-service concrete structures are normally exposed to varying temperature condition. The time-dependent and non-uniform temperature distribution in concrete structures could affect the accurate assessment of their electrical properties. Therefore, the influences of temperature change over time and the spatial variation in temperature on the measured electrical resistance of cementitious materials are still in need of investigation. The coupled thermal-electrical responses of two types of cementitious materials under varying temperature history were investigated by a series of thermal and electrical tests in this study. Then a coupled thermal-electrical finite element (FE) model was developed to simulate the coupled thermal-electrical responses. The results show that the input direct current has a minor effect on the measured electrical resistance by embedded four-probe method and the specimen temperature when it is no greater than 3 mA. The relationship between the measured temperature at 10-mm depth of the specimen and the apparent resistance is well captured by a linear equation. The coupled thermal-electrical finite element model can predict well the developments of specimen temperature and apparent electrical resistance under varying temperature history. The FE results reveal that the non-uniform temperature variation results in the redistribution of electrical current within the tested specimen. However, electrical field between the two inner electrodes is always uniform when the embedded four-probe method is used, which is not affected by the non-uniform temperature variation.

Modeling and research on high-frequency AC heating system for lithium-ion battery based on bidirectional buck-boost topology

Lithium-ion battery (LIB) performance decreases in cold climates, preheating is necessary to improve the output power and life decay of low-temperature LIB. At present, a variety of internal alternative current (AC) heating methods are used to achieve fast and temperature-consistent heating. However, existing AC heating devices are constrained by the problems of changing the battery structure, and also need for an additional power supply to power the battery, which have effect on the battery life. Meanwhile, the conventional model is not suitable for AC preheating simulation, especially at high frequencies. Under above scenarios, a high-frequency AC heating method using a bidirectional boost converter is designed and a high-frequency thermoelectric model based on lithium-ion transmission is developed. In the paper, the proposed high-frequency AC heating structure and thermal-electrical coupling model are verified by experimental results to test the validity of different AC heating frequencies, which solves the lack of comprehensive theoretical and experimental verification in the field of high-frequency AC heating. The experimental results show that increasing the AC heating frequency at the same current multiplicity can significantly increase the heating rate. An optimal frequency is acquired, the optimal heating rate can reach 4.65 K/min at 800 Hz without affecting the service life of the battery. The high-frequency AC heating method provides a new solution framework for the LIB performance enhancement in cold climates.

Impact of surrounding tissue-type and peri-electrode gap in stereoelectroencephalography guided (SEEG) radiofrequency thermocoagulation (RF-TC): a computational study

Purpose To use computational modeling to provide a complete and logical description of the electrical and thermal behavior during stereoelectroencephalography-guided (SEEG) radiofrequency thermo­coagulation (RF-TC). Methods A coupled electrical-thermal model was used to obtain the temperature distributions in the tissue during RF-TC. The computer model was first validated by an ex vivo model based on liver fragments and later used to study the impact of three different factors on the coagulation zone size: 1) the difference in the tissue surrounding the electrode (gray/white matter), 2) the presence of a peri-electrode gap occupied by cerebrospinal fluid (CSF), and 3) the energy setting used (power-duration). Results The model built for the experimental validation was able to predict both the evolution of impedance and the short diameter of the coagulation zone (error < 0.01 mm) reasonably well but overestimated the long diameter by 2 − 3 mm. After adapting the model to clinical conditions, the simulation showed that: 1) Impedance roll-off limited the coagulation size but involved overheating (around 100 °C); 2) The type of tissue around the contacts (gray vs. white matter) had a moderate impact on the coagulation size (maximum difference 0.84 mm), and 3) the peri-electrode gap considerably altered the temperature distributions, avoided overheating, although the diameter of the coagulation zone was not very different from the no-gap case (<0.2 mm). Conclusions This study showed that computer modeling, especially subject- and scenario-specific modeling, can be used to estimate in advance the electrical and thermal performance of the RF-TC in brain tissue.

Comprehensive comparison and applicable range of separating and coupling numerical models of thermoelectric generation device for waste heat recovery

There are two different numerical modelling approaches of thermoelectric generation (TEG) device: separating model that is one-way coupling from CFD model to thermal-electric model and coupling model that is two-way coupling between CFD model and thermal-electric model. With the change of application conditions, the TEG device is subjected extensive changes of fluid parameters. To determine the applicable fluid range of sharing two models of TEG device, a comprehensive comparison between two models is conducted in this study. The results indicated that for the coupling numerical model, the Peltier heat has a negative effect on the temperature difference and output performance of thermoelectric module compared with the prediction results of separating numerical model. Therefore, an output error is induced between the prediction results of separating and coupling numerical models. This error can be decreased by increasing fluid mass flow rate and decreasing fluid temperature. Consequently, the applicable fluid ranges of sharing two models are divided by setting the different error bounds. It is suggested that the separating numerical model is given priority to reduce the calculation complexity when the fluid range of practical application is within a small error bound.

On the Existence of a Nonextendable Solution of the Cauchy problem for a $$(1+1)$$-Dimensional Thermal-Electrical Model

On the Existence of a Nonextendable Solution of the Cauchy problem for a $$(1+1)$$-Dimensional Thermal-Electrical Model

Editor's Note for article entitled “An online temperature estimation for cylindrical lithium-ion batteries based on simplified distribution electrical-thermal model”

Editor's Note for article entitled “An online temperature estimation for cylindrical lithium-ion batteries based on simplified distribution electrical-thermal model”

Thermal-electric modelling and multi-state joint parameter identification of lithium-ion batteries

This paper proposes a model for the characterization of thermal-electric properties of lithium-ion batteries. The model achieves high accuracy estimation of the temperature and voltage-current characteristics of the battery considering thermal electric coupling. A second-order equivalent circuit model and a lumped-parameters thermal model are developed to capture the electric and temperature characteristics of the cell separately. A polynomial product equation is proposed to capture the relationship between battery temperature and state of charge for the purpose of describing the interactions of thermal and electric parameters during the charging/discharging processes. Experimental data of an NCR18650B lithium-ion battery cell are gathered in laboratory tests and used for parameter estimation of the model built in the paper. Compared with the existing thermal-electric coupling models that rely on a look-up table, the model proposed achieves better accuracy in terms of temperature and voltage-current characteristics estimation.

On the blow-up of the solution of a $$(1+1)$$-dimensional thermal–electrical model

On the blow-up of the solution of a $$(1+1)$$-dimensional thermal–electrical model

On the blow-up of the solution of a $(1+1)$-dimensional thermal-electrical model

Рассматривается тепло-электрическая $(1+1)$-мерная модель нагрева полупроводника в электрическом поле. Для соответствующей начально-краевой задачи доказано существование непродолжаемого во времени классического решения и получены достаточные условия разрушения решения за конечное время.

Multi-objective optimization strategy for multipolar magnesium electrolysis cell based on thermal-electric model

In the operation of industrial multipolar magnesium electrolysis cell, cell voltage and current density are important indicators of the production performance of the cell, while thermal balance is a key factor for normal operation. This paper utilizes the finite element method to establish a three-dimensional full cell thermal-electric model, studying the thermal field distribution and current density distribution in a 165kA multipolar magnesium electrolysis cell. Based on the heat balance of the multipolar cell, the influence of structural parameters on current intensity, average current density at the anode surface and resistance voltage is assessed. Dimensionless analysis yielded optimization criteria, and the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was employed for multi-objective optimization problems. When stringent optimization is executed, significant performance improvements can be achieved in terms of the electrolysis cell's resistance voltage and current density. Moreover, under the optimization criteria, the relative error of the 265kA multipolar magnesium electrolysis cell model is less than 1 %. The results indicate that the workflow combining the finite element method with multi-objective optimization algorithms can be applied to the optimization and scale-up design of high-current multipolar magnesium electrolysis cell.

Integrated Model for Comprehensive Performance Investigation of Solar Concentrated Photovoltaic‐Thermal System Embedded with Microchannel Heat Sinks

Concentrated photovoltaic (CPV) is a well‐established renewable energy technology. A significant challenge in CPV systems is their low efficiency, majorly due to localized heating yielded from concentration, often requiring the use of cooling systems. The accurate performance analysis and cooling system design for CPV systems require a multiphysics model. Herein, an integrated optical–thermal–electrical model is proposed for the performance evaluation of CPV systems incorporated with different configurations of microchannel heat sinks. The heat sink configuration includes 116 parallel and counter microchannels (Configuration A and B), a single wide microchannel (Configuration C), and single wide minichannel (Configuration D) heat sinks. This study involves 3D Monte‐Carlo ray tracing, finite volume method, and cell‐based electrical modeling. The results indicate that the flux profile over the absorber is highly nonuniform in nature. Furthermore, the CPV system with a Configuration C heat sink achieves a better uniformity in temperature, providing an optimized thermal performance of 64.63%. Moreover, the integrated model considers the impact of PV cell current mismatch that becomes prominent at increasing incidence angles. A maximum deviation of 6.9% in electrical power is obtained while comparing predicted numerical results against experimental results available in literature.

The driving characteristics of bidirectional SMA wire actuators - Theoretical modeling and experimental testing

Bidirectional shape memory alloy (SMA) wire actuators play a critical role in driving applications thanks to their characteristics in memory shaping and good overall performance. SMA wire actuators were often studied at a single load type, and there is no comprehensive comparison investigation of different SMA wire actuators in the literature. In this paper, the driving characteristics of four available types of SMA wire actuators, namely, dead-load, biased spring, differential type, and biased superelastic SMA wire actuators are modelled mathematically and then tested in laboratory settings. The characteristics of SMA wire actuators are quantitatively measured and then compared under a range of application scenarios. The output displacement and thermal-electric models of NiTi SMA wires are derived based on the Brinson constitutive model with stress effects in consideration. A customized SMA wire actuator test device is developed to evaluate the theocratical models and benchmark testing four types of SMA wires and their driving characteristics, including structure, design, displacement, response and recovery time, energy efficiency and hysteresis properties. The SMA wire phase transformation characteristics of the four actuators are tested under different activation currents, and then quantitatively compared. In conclusion, this paper adds theoretical and experimental significance to the literature on SMA wire actuators. The reference value on the phase transformation characteristics of SMA wires can be used to guide SMA application in industrial designs and enable theoretical studies in complementary research areas.

Electrical-thermal modeling and electrical design optimization of fuses in a nickel bus-plate for a Li-ion battery pack

This paper presents a two-dimensional thermal-electrical coupled steady-state physics-based finite-element model developed to analyze Nickel 201 (Ni201) bus-plates for a novel 134P battery pack design, where a 1.4C current was applied per cell. Two modeling approaches were used: one with an out-of-plane current density boundary condition inserted in the charge conservation equation and a second one with a constant voltage boundary condition calculated at each battery tab. Both positive and negative-bus plate designs were analyzed. Electric resistance measurements were used to validate the model and the two modeling approaches. This study demonstrated that a nickel bus plate design can be optimized, without the addition of extra material or substantive geometry changes, by clocking the fuses and weld tab connections towards the direction of the closest terminal connection point. The resulting geometry, mimicking a sunflower formation, can reduce the internal resistance of the bus plate by at least 15 %, regardless of the modeling approach used.

Transformer hot spot temperature estimation through adaptive neuro fuzzy inference system approach

Transformer performance and efficiency can be enhanced by effectively address the properties of its insulation system. The power transformer insulation system weakens as a result of operational thermal stresses brought on by dynamic loading and shifting environmental patterns. Winding hot spot temperature is a crucial metric that must be maintained below the prescribed limit while power transformers are operating so as to maintained power system reliability. This is due to the fact that, among other variables, the time-dependent aging effect of insulation depends on transitions in hot spot temperatures. Due to the non‐linear nature of the conventional mathematical models used to determine these temperatures, and complexity of thermal phenomena, investigations still need to be exercised to fully understand the variables that associate with hot spot temperature computation with minimum error. This paper explores the possibilities of enhancing top oil and hot spot temperature estimation accuracy through the use of an adaptive neuro-fuzzy inference (ANFIS) technique. The paper presents an adaptive neuro fuzzy model to approximate the hot spot temperature of a mineral oil-filled power transformer based on loading, and established top oil temperature. Initially, a sub-ANFIS top oil temperature estimation model based on loading and ambient temperature as inputs is established. Using a hybrid optimization technique, the ANFIS membership functions were fine-tuned throughout the training process to reduce the difference between the actual and anticipated outcomes. The correctness and reliability of the created adaptive neural fuzzy model have been verified using real-world field data from a 60/90MVA, 132 kV power transformers under dynamic operating regimes. The ANFIS model results were validated against field measured values and literature-based electrical-thermal analogous models, establishing a precise input-output correlation. The developed ANFIS model achieves the highest coefficient of determination for both TOT and HST (0.98 and 0.96) and the lowest mean square error (7.8 and 10.3) among the compared thermal models. Correct determination of HST can help asset managers in thermal analysis trending of the in-service transformers, helping them to make proper loading recommendations for safeguarding the asset.

Electrical-Thermal Coupling Modeling of SiC MOSFETs Based on Field-Circuit Coupling and Its Application in Junction Temperature Calculation during Surges

Electrical-Thermal Coupling Modeling of SiC MOSFETs Based on Field-Circuit Coupling and Its Application in Junction Temperature Calculation during Surges

A Review of Cooling Technologies in Lithium-Ion Power Battery Thermal Management Systems for New Energy Vehicles

The power battery is an important component of new energy vehicles, and thermal safety is the key issue in its development. During charging and discharging, how to enhance the rapid and uniform heat dissipation of power batteries has become a hotspot. This paper briefly introduces the heat generation mechanism and models, and emphatically summarizes the main principle, research focuses, and development trends of cooling technologies in the thermal management of power batteries in new energy vehicles in the past few years. Currently, the commonly used models for battery heat generation are the electrochemical-thermal model and the electrical-thermal model. Scholars have conducted more research based on multidimensional electrochemical-thermal/electrical-thermal models because taking the actual characteristics of the battery into account can provide a more comprehensive and systematic description. Among various cooling technologies, the air-cooling system boasts the most economical manufacturing costs and a compact, reliable structure. The heat transfer coefficient of the liquid-cooling system is very high, while the temperature remains uniform in the PCMs cooling system during the material phase transition process. Against the background of increasing energy density in future batteries, immersion liquid phase change cooling technology has great development prospects, but it needs to overcome limitations such as high cost and heavy weight. Therefore, the current lithium-ion battery thermal management technology that combines multiple cooling systems is the main development direction. Suitable cooling methods can be selected and combined based on the advantages and disadvantages of different cooling technologies to meet the thermal management needs of different users.

On the Blow-Up of the Solution of a Nonlinear System of Equations of a Thermal-Electrical Model

On the Blow-Up of the Solution of a Nonlinear System of Equations of a Thermal-Electrical Model