Temperature Rise Characteristics Research Articles

Temperature Rise Characteristics Research of Integrated Electric Drive System for Vehicles

Temperature Rise Characteristics Research of Integrated Electric Drive System for Vehicles

Characterization of hydrogen refueling temperature rise of the on-board hydrogen system under different failure modes

Fuel cell vehicles (FCVs) have the advantages of pollution-free, and excellent fuel economy. However, rapid hydrogen filling will cause the temperature inside the hydrogen cylinder to rise rapidly. The failure of some components of the on-board hydrogen system (OBHS) will increase the accident rate of FCVs during rapid refueling. Valves and pipelines are ignored during the hydrogen filling mode establishment, thereinto the automatic tank valve and hydrogen dispenser are prone to failure due to loose parts, sensor failure, and other problems. In this paper, a two-dimensional (2D) planar computational fluid dynamics (CFD) model is established to simulate and analyze three kinds of failures, such as hydrogen filling blockage, excessive hydrogen filling, and excessive hydrogen flow, to study the temperature rise characteristics of the OBHS. The results show that the failures of excessive hydrogen filling and excessive hydrogen flow are more likely to cause the final temperature of the hydrogen cylinders to exceed 358 K. The maximum temperature of the OBHS caused by excessive hydrogen flow rate is 5.7 % (21 K) and 0.8 % (3 K) higher than hydrogen filling blockage and excessive hydrogen filling, respectively. This indicates that, contrary to what other studies have not found, the hydrogen filling flow has a greater impact on the temperature rise of the hydrogen cylinder than the hydrogen filling pressure and inlet pipe diameter.

Research on multi-physical field analysis and assessment technique of virtual connection defects in cluster cable joints based on digital twin technology

As the “blood vessels” and “nerves” of the power grid, cables are important carriers for transmitting electric energy, and their failures will affect the safe and stable operation of the power grid. In this paper, a digital twin model of thermal characteristics is constructed for 10 kV YJV×400 cluster cable and its joint model. Based on the multi-physical field coupling analysis method, the fluid field, temperature field and current-carrying capacity of the cluster cable are analyzed. The temperature rise and airflow distribution characteristics of the joint and its external insulation when the defect of joint false connection occurs are analyzed. Based on the fuzzy analytic hierarchy process (FAHP), weights are assigned to the locations of multiple measurement points of the cable external insulation, and the temperature distribution of each measurement point is combined with the digital twin technology to calculate the hot spot temperature of the cable, so as to assess the defects of the joints of the cables. The digital twin platform is used for real-time monitoring of cable status and assessment of defects. The temperature rise experiments of cables under different carrying capacity and joint defects show that this method can accurately and efficiently calculate hot spot temperatures and assess defects of joints in cluster cables.

Temperature Field Characterization of Iron Tailings Based on Microwave Maintenance Technology.

Microwave maintenance technology, as a new development trend, can realize the environmentally noninvasive and rapid repair of asphalt pavement and gradually replace traditional maintenance methods. Iron tailings were used as a self-healing material in this study to investigate the temperature response matching of microwave maintenance technology. Firstly, the physical properties and the mechanism of iron tailings were elaborated through macroscopic physical index testing and microscopic X-ray diffraction (XRD) analysis. Secondly, the applicability of aggregates to microwave heating was demonstrated by analyzing the temperature rise characteristics of the granules using infrared imaging. Then, the temperature field variation rules of the iron tailing asphalt mixture were summarized by microwave heating Marshall specimens. Finally, the road performance was assessed by conducting high-temperature dynamic stability, low-temperature tensile, water immersion Marshall, and freeze-thaw splitting tests. The experimental results showed that the iron tailings can be used as an aggregate for high-grade asphalt pavement and as the preferred aggregate for microwave maintenance technology. The iron tailings temperature field was radial from the inside out to provide different temperature response states for different pavement diseases, so the asphalt was dissolved and precipitated in a short time. The particle size of iron tailings was inversely proportional to the wave-absorbing heating rate, and the heating efficiency of the small particle size (0-4.75 mm) was the highest. The specimens doped with 4.75-13.2 mm iron tailings showed the best heating performance and road performance, with the average surface temperature of the specimens reaching 126.0 °C within 2 min. In summary, according to different disease types and construction needs, iron tailings can be used as an aggregate for asphalt pavement, providing an appropriate temperature field and improving the efficiency of the microwave maintenance of asphalt pavements.

Analysis and experimental research of transient temperature rise characteristics of high-speed cylindrical roller bearing

In this paper, on one hand, the time-varying characteristics of the heat source and thermal boundary conditions of the high-speed spindle system were analyzed considering the thermal-structural coupling effect. And a transient bearing temperature field prediction method combining the thermal network method and finite element method was proposed. Furthermore, the relationships between time step, calculation efficiency and calculation results were analyzed. On the other hand, a online real-time monitoring system of the transient temperature of the cylindrical roller bearing inner ring for maximum speed of 13,000 r/min was designed and implemented using fibre optic sensing technology. Comparing with the conventional static thermal analysis results, it is verified that the simulation method proposed in this paper has higher accuracy. This paper provides a new approach for analysing and testing the thermal characteristics of high-speed spindle system.

Research on temperature rise characteristics and hot spot temperature inversion method of oil-immersed transformer based on coupling of magnetic-fluid-thermal field

The hot spot temperature is an important factor affecting the operation state and insulation life of oil-immersed transformer. It is of great value to carry out multi-physical field coupling simulation research on magnetic-fluid-thermal field of oil-immersed transformer and accurately calculate and predict the hot spot temperature of transformer for transformer service life evaluation. In this paper, the oil immersed transformer is taken as the research object, and five characteristic parameters of the hysteresis model are obtained by using PSO optimization algorithm according to the experimental magnetic characteristics data of the core material and the classical J-A hysteresis model, A 3D simulation model of magnetic-fluid-thermal field is established based on the electrical and structural parameters of the oil-immersed transformer. Combined with the magnetic characteristics of the core material, the thermal field and the surrounding fluid distribution of the transformer core and winding are obtained by two-way coupling method. On this basis, in order to accurately reflect the correlation between the hot spot temperature of the transformer winding and the temperature of the oil tank wall, the selection position of the characteristic temperature point of the transformer tank wall is determined by streamline analysis method, and the hot spot temperature of the oil-immersed transformer is retrieved by support vector machine method. The results show that the prediction accuracy of the hot spot temperature reaches 0.998, and the inversion method has a high enough accuracy. It provides theoretical basis and technical support for real-time monitoring of hot spot temperature in oil-immersed transformer windings.

Enhancement of ductility of cold-deformed 316L stainless steel by electric pulse treatment

In this study, we performed electric pulse treatment (EPT) on the cold-deformed 316L stainless steel. The effects of EPT on the temperature rise characteristics, tensile properties and microstructure of cold-deformed 316L SS were investigated. The results show that changes in current density have a significant effect on the surface temperature and tensile properties. Compared with the UT samples, at a current density of 44 A/mm2, the elongation after fracture reached a peak of 39.8% (the enhancement rate is 14.4%), while the ultimate tensile strength of all the EPTed samples shows no significant change. Interestingly, although the sample experienced an increase in temperature during the EPT process, the phase composition and grain structure remained unchanged significantly. This implies that the improvement in the ductility of the samples may be attributed to the reduction of micropores. The present research provides new light to the enhancement of ductility of cold-deformed 316L stainless steel.

Thermal Response Characteristics of Concrete-Filled Steel Tube Columns with Flame Encapsulation Thickness

In order to elucidate the influence of flame encapsulation thickness on the thermal response characteristics of concrete-filled steel tube columns in a fire environment, a study was conducted focusing on the primary control mechanism of heat radiation power from fire——the thickness of fire encapsulation. The thermal resistance effect at the interface between the steel tube and concrete, as well as the temperature rise characteristics of the flame, were comprehensively considered. A calculation method was established for the thermal response characteristics of concrete-filled steel tube columns under different flame encapsulation thickness conditions, providing support for the simulation of thermal response and temperature rise prediction of concrete-filled steel tube columns in fires. The results indicate that the flame emissivity and radiant heat power increase with the increase of flame encapsulation thickness. As the flame encapsulation thickness gradually increases, the growth trend of flame radiant power slows down. When the flame encapsulation thickness L < 1 m, the temperature rise rate of the concrete-filled steel tube column is significant. When the flame encapsulation thickness L ≥ 1 m, the temperature rise rate of the concrete-filled steel tube column tends towards a constant value.

STUDY ON VIBRATION AND TEMPERATURE RISE CHARACTERISTICS OF FULL CERAMIC BALL BEARINGS UNDER HIGH-TEMPERATURE CONDITIONS

In order to study the vibration and temperature rise characteristics of full ceramic ball bearings under high-temperature conditions, the bearing vibration test of a simulated high-temperature environment was conducted in this paper. The vibration and temperature rise properties of full ceramic ball bearings were measured under high-temperature variable working conditions in this experiment. The results demonstrate that the temperature rise and vibration acceleration of full ceramic ball bearings increase with the cavity temperature increasing from 50°C under a single load. The vibration and temperature rise increased with an increase in rotational speed. Due to the mechanical characteristics of a silicon nitride material, the change of temperature rise of a full ceramic ball bearing is relatively small. When temperature and speed were stable or only very low, full ceramic ball bearings operated stably. The results of the experiment can serve as a guide for the operational state of full ceramic ball bearings in high-temperature environments.

Study on the temperature rise characteristics of aging lithium-ion batteries under different cooling methods

Lithium-ion batteries have been widely used in electric vehicles and electrochemical energy storage power stations. With the increase of service time, the single cells in the battery module will age to varying degrees, resulting in inhomogeneous heat generation and even safety accidents. Considering that there is currently limited research on the cooling effect of battery cooling technology on aging batteries, this article adopts a new non-destructive method to study the uneven aging characteristics and the temperature rise characteristics under different cooling conditions of different cells in small aging lithium-ion battery modules. The results show that the irreversible heat generation power of cell 1, cell 2 and cell 3 during 1 C discharge is 1.23 W, 1.33 W and 1.15 W, respectively, showing different degrees of aging. However, the maximum temperature rise under natural heat dissipation conditions has the same change trend and the average temperature rise on the surface of three cells at the end of discharge is about 20 °C. The temperature rise at the edge of cell 2 and cell 1 with more serious aging is higher, while the temperature rise at the center of cell 3 with the smallest aging degree is higher. The temperature distribution at different positions on the surface of the three cells was slightly different. The maximum temperature difference at different positions on the surface of cell 2 (2.3 °C) was greater than that of cell 1 (1.5 °C) and cell 3 (1.6 °C). Then, a simple OCV test method and SEM characterization technique were used to analyze the aging characteristics of the electrode position corresponding to the external temperature monitoring position of cell 2, and the relationship between temperature distribution and aging characteristics was established. The cooling and uniform temperature ability of thermal pad, semiconductor cooling and liquid cooling plate/semiconductor composite cooling are improved in turn. Among them, the liquid cooling plate/semiconductor composite cooling is an efficient temperature control strategy which can make the temperature of cell 3 basically stable at 23 ° C during 1C discharge by reasonably regulating the cooling power, and the maximum surface temperature difference is maintained at 0.4 ° C. It is suggested that when the large cell is put into use, it should be equipped with an independent sub-regional precise temperature control system that can adjust the cooling power in real time according to the heat production rate of the battery, so as to improve the safety and promote the development of sustainable energy.

An Accurate Electro-Thermal Coupling Model of a GaAs HBT Device under Floating Heat Source Disturbances.

Taking into consideration the inaccurate temperature predictions in traditional thermal models of power devices, we undertook a study on the temperature rise characteristics of heterojunction bipolar transistors (HBTs) with a two-dimensional cross-sectional structure including a sub-collector region. We developed a current-adjusted polynomial electro-thermal coupling model based on investigating floating heat sources. This model was developed using precise simulation data acquired from SILVACO (Santa Clara, CA, USA). Additionally, we utilized COMSOL software (version 5.6) to simulate the temperature distribution within parallel power cells, examining further impacts resulting from thermal coupling. The research findings indicate that the rise in current induces modifications in the local carrier concentration, thereby prompting variations in the local electric field, including changes in the heat source's peak location and intensity. The device's peak temperature exhibits a non-linear trend regulated by the current, revealing an error margin of less than 1.5% in the proposed current-corrected model. At higher current levels, the drift of the heat source leads to an increase in the heat dissipation path and reduces the coupling strength between parallel devices. Experiments were performed on 64 GaAs (gallium arsenide) HBT-based power cells using a QFI infrared imaging system. Compared to the traditional temperature calculation model, the proposed model increased the accuracy by 6.84%, allowing for more precise predictions of transistor peak temperatures in high-power applications.

Radiative transfer model and validation for infrared management optical properties of porous polymer materials incorporating impacts of micro-voids

In order to characterize the infrared (IR) radiation absorption and/or emission performances of functional porous polymers which claim to have healthcare functions due to IR excitation and emission by processing technologies, a radiative transfer model was constructed based on the principle of IR radiation, the Beer–Lambert law, the Fresnel’s formula and Planck’s law. The theoretical analysis was conducted for the IR management optical properties of the porous sheet polymer materials, including IR reflection, transmission, absorption and emission behaviours during the dynamic process of IR radiation. A modeling method for characterization and revealing of IR management optical properties and optical and thermal transfer behaviours of the reflection and transmission was then investigated from the structural parameters and the temperature rise characteristics of the porous sheet polymer materials during the dynamic IR radiation process. The model was validated by comparing the predicted values from the radiative transfer model with the measured values from the test results of the validation experiments of eight typical porous sheet polymers in an experimental setup. The model was modified by consideration of the influences of two types of micro-voids defects represented by the porosity of micro structure and the thickness compression ratio. The micro-voids defects factors were added to the structural parameters, and therefore the model was improved and the maximum prediction errors of the transmission and reflection surfaces were mostly less than 10%. The radiative transfer model provides the theoretical fundamentals for the evaluation and guidance of IR management optical performances for new products design, development, fabrication and processing in industrial application of functional porous polymers.

Study on temperature rise characteristics of DC charging cable for electric vehicles

In order to accurately calculate the relationship between the loading current and temperature rise of DC charging cable of electric vehicles, this article establishes the equivalent thermal circuit model of DC charging cable of electric vehicle based on the thermal circuit model analysis method, and refers to the principle of adaptive filtering, proposes a method to derive the thermal circuit model parameters of DC charging cable of electric vehicle from the actual temperature rise data, and designs a comparison experiments to verify the accuracy of the thermal circuit model of DC charging cable obtained by this method. The experimental results show that the calculation temperature rise and actual temperature rise error of the EV charging cable thermal circuit model obtained by deriving from the actual temperature rise data in this article is small, which verifies that the EV DC charging cable thermal circuit model obtained by this method has a certain accuracy in analyzing the temperature rise of this type of cable.

Design of the water-cooling structure for the 100 kA DC mechanical switch in the CRAFT quench protection system

The DC mechanical switch is connected in series with the superconducting magnet in the quench protection system. As the main switch that carries the magnet current for a long time, the temperature of its conductive unit, especially the contact part, inevitably increases significantly during operation. It is necessary to design a water-cooled structure to control the temperature rise. This article introduces the structural design of the conductive unit of the DC mechanical switch for the Comprehensive Research Facility for Fusion Technology quench protection system and uses a combination of theoretical calculation, thermal-electrical coupling simulation, and Fluent simulation to analyze the thermal stability characteristics at a current level of 100 kA. By comparing and studying the temperature rise characteristics of switches under different cooling paths, diameters of water-cooling pipe, and water flow rates, a design basis is provided for determining a 15 mm diameter “∏” shaped cooling water path structure for the mechanical switch. The DC mechanical switch water-cooled structure designed in this article is expected to effectively control the temperature rise level of the contact.

Fire Characteristics of Lithium-ion Battery According to the State of Charge in an Accelerating Rate Calorimeter

Recently, the interest in ecofriendly energy as an alternative to fossil fuels, which cause climate change and sea level rise, has increased. To achieve the efficient utilization of ecofriendly energy, such as a renewable energy, considerable effort has been made to use energy storage systems (ESSs) and smart grid systems. However, many safety problems, such as battery fires caused by the increase in the use of secondary batteries, significantly limit their application scope. In this study, to investigate the fire characteristics of lithium ion batteries (LIBs), the characteristics of the spontaneous exothermic reaction and thermal runaway phenomenon that occur at each temperature of an LIB battery were investigated using an accelerating rate calorimeter. The batteries used in the experiments were standard 18650 cylindrical batteries with a capacity of 2600 mAh, and they were tested at three different state-of-charge (SOC) levels: 0%, 50%, and 100%. The type of heat generated by each experimental condition was classified into four stages, and the existence and temperature rise characteristics of each stage were investigated according to the SOC. Although thermal runaway occurred at both 50% and 100% SOC, the reaction at 50% SOC did not escalate into violent explosions like the reaction observed at 100% charging. Furthermore, the activation energies for the thermal runaway observed in the experiments conducted at 50% and 100% SOC are presented.

Judgment method of the dynamic threshold value of motor protection at a dynamic load rate

To address the shortcomings of traditional motor thermal protection, which uses the motor’s temperature or temperature rise threshold operating at full load as the basis for the judgment method, a dynamic threshold judgment method based on a study of the motor’s temperature rise characteristics under a dynamic load rate is proposed. Taking a forced air-cooled, three-phase asynchronous motor with 11 kW power as the research object, a 2D/3D motor model under steady-state conditions is established. The loss distribution of asynchronous motors at different load rates is obtained through electromagnetic field simulation calculations. The finite element method is used to simulate and calculate the motor’s temperature field. Taking ambient temperature and load factors into account, the study takes place from the perspective of motor temperature rise in order to acquire the law governing the change in motor temperature increase under various working circumstances. A method of converting the temperature and warming between the motor’s stator, winding, and rotor is proposed. A dynamic threshold judgment system for accurate warning of overheating problems in motors under any load rate is set up so that the thermal protection of motors can accurately be judged under variable load conditions, which offers a crucial theoretical foundation for the design of intelligent motor temperature rise prediction systems. It contributes to a methodological underpinning for the diagnosis and early warning of thermal health in smart motor systems.

Modeling, heat dissipation design, and force tracking control for temperature-dependent hysteresis of magnetorheological damper

The temperature-dependence (T-dependence) characteristics of magnetorheological fluids (MRFs) cause the damping force of magnetorheological dampers (MRDs) to change with temperature. The rapid temperature rise can lead to performance degradation or even failure of MRFs, reduced damping force of MRDs, and decline in control performance. In this paper, numerical simulations and predictions of the temperature rise characteristics of the MRD are performed and heat sinks are designed and optimized. The experimental results verify the efficiency of the simulations and predictions, and the heat sinks can significantly reduce the rate of temperature increase and improve the ability of the damper to operate for long hours. In order to accurately compensate for T-dependence characteristics of the MRD, a T-dependence hysteresis model and a model-based feedforward force tracking control method with disturbance observation of the MRD are proposed and validated by experiments. The experimental results indicate that the proposed T-dependence model has better prediction accuracy than the general hysteresis model, and the feedforward control method achieves good force tracking performance even without expensive force sensors.

Analytical investigation of solar parabolic trough receiver with multiple twisted tapes using exergy and energy analysis

Exergy analysis is an important thermodynamic approach to studying the system's actual output, considering all losses. The present study is an analytical approach to calculating the thermal and exergetic efficiencies of the parabolic trough receiver using MATLAB R2018a simulation software. These efficiencies are evaluated considering temperature rise characteristics and parametric design factors. The influence of the solar air heater's thermal and exergy analysis-based mathematical model on all design parameters is examined. The receiver tube has multiple twisted tape inserts with three varying parameters, i.e., twist ratio (y/w) = 3 to 5, perforation ratio (dp/w) = 0.05 to 0.25, and winglet ratio (d/w) = 0.1 to 0.3. The twisted tape with y/w, dp/w, and d/w having values 3, 0.1, and 0.05 perform better regarding energy and exergy with values 84.27% and 4.28%, respectively. This thorough examination can prove to be highly effective and advantageous in generating the design model for the specified twisted tape parameter value without requiring extensive investment in actual experimentation while also furnishing an evaluation of the performance of the solar air heater design.

Effect of low-temperature pre-oxidation on the self-heating of coal

In order to investigate the effect of low-temperature pre-oxidation on the self-heating of coal, research was made on the temperature rise characteristics of coal samples with different pre-oxidation temperatures, duration and numbers. Besides, in situ FTIR and ESR experiments were also carried out to study changes in active groups and free radicals of raw and pre-oxidized coal. Results show that the pre-oxidation in the 30–60 °C temperature range markedly reduces the oxidation activity of coal and inhibits the oxidation reaction. TTR (total temperature rise) of the pre-oxidized coal is inversely proportional to pre-oxidation temperature, duration and number. The hydroxyl and aliphatic hydrocarbons continue to decrease in content during the oxidation reaction. The C-O group and carbonyl group, as the main oxidation products, show an increasing trend. The trend of group content in the pre-oxidized coal samples is significantly smaller than that of the raw coal, indicating the activity of active groups is weakened. The variation in Ng for coal samples decreases eventually after pre-oxidation, suggesting that initial oxidation makes the coal molecular structure more stable. This study helps to understand further the effect of low-temperature pre-oxidation on the self-heating of coal and provides a theoretical basis to use the pre-oxidation method to prevent coal spontaneous combustion.

Type of the study: Original research article relationship between temperature rise characteristics and the emission of carbon oxides during the spontaneous combustion latency of coal

The emission of carbon oxides during the spontaneous combustion latency of coal poses a severe challenge to the ecological and geological environmental protection of mining areas. Owing to the insidious nature of latency, the oxidative characteristics during this stage have rarely been studied. This study investigated the relationship between temperature rise characteristics and the emission of carbon oxides under different coal samples, initial temperatures, and particle sizes. The results indicated that the formation of carbon oxides correlated with the temperature rise characteristics during latency. Time-dependent carbon oxide formation followed an exponential function y=aexp(xb)+c. The metamorphic degree and initial temperature of the coal had a significant impact on the CO2/CO ratio and the particle size was independent of the ratio. In addition, in-situ Fourier transform infrared reflection experiments on four coal samples revealed that the hydroxyl, aliphatic hydrocarbon methyl, and methylene groups are key active groups in carbon oxide formation during latency, providing the original heat source for coal oxidation. The carbonyl and carboxyl groups acted as reactants and products and their content varied irregularly during oxidation. These results improve the understanding of CO and CO2 emissions from coal oxidation during spontaneous combustion latency and will aid early prevention of coal spontaneous combustion.