Analysis Of Thermal Characteristics Research Articles

Comparative analysis of thermal characteristics of higher fullerenes when heated in a nitrogen atmosphere

To study the behavior of higher fullerenes Cn (n = 84, 90, 94) under thermal exposure in a nitrogen medium, a thermodynamic modeling method is used, the main task of which is to determine the phase, chemical composition and parameters of the system under study. This method consists of analyzing the system using the TERRA program, which is a further development of the ASTRA program package. For Cn-N2 systems, a comparative study of ongoing chemical reactions was carried out. Intervals of thermal stability of the condensed phase for higher fullerenes are revealed. The periods of thermal destruction in the gas phase in the systems under consideration are determined.

Influence of Traction Motor Components on Thermal Characteristics of Traction Motor Bearings

The operating temperature and thermal stress play key roles in overall performance of a cylindrical roller bearing used in high-speed train traction motor. The cylindrical roller bearing studied in this paper is in the housing of the traction motor. Due to the heating of each component of the traction motor, a thermal environment is formed in the housing that changes the temperature and stress of the traction motor bearing. In this paper, a thermal-mechanical coupled model of bearing considering the stator, rotor, and shaft was established to study the temperature and thermal stress of traction motor bearing. Experiments were conducted on a service high-speed train to validate the proposed bearing thermal analysis model, meanwhile, the temperature of the measurement point was revised by the theory of heat transfer. The revised experiment results show that the established thermal-mechanical coupled model is reasonable and effective. The results show that the heating of the stator and rotor of the traction motor has a great influence on the temperature and stress of the cylindrical roller bearing of the traction motor. When the heating of the stator and rotor is considered, the temperature of inner ring near the traction motor is higher than that of far away from the traction motor, and the overall temperature of each component of the bearing also increases. As for the stress, when the traction motor stator and rotor is considered, the maximum stress increases by 66.9%. Therefore, the heating of the stator of the traction motor must be considered when the thermal characteristics analysis and reliability analysis are carried out on the cylindrical roller bearing.

Analysis of Thermal and Flow Characteristics in a Combined Cross-Flow and Jet-Flow Configuration with Flow-Guiding Fins

This study investigated the enhanced cooling of electronic components at high temperatures with cross-flow and jet-flow combinations. The cooling performance of four different model geometries (Models 1, 2, 3, and 4) of an electronic component was analysed by considering different jet-to-channel inlet velocity ratios (Vj/Vc) and ratios of the distance between the jet and impinging surface to jet diameter (H/D). The Vj/Vc and H/D ratios were varied in the 0–3 and 2–4 ranges, respectively, in the computational fluid dynamics analysis. The thermal and flow characteristics were revealed through a comparative result analysis, also considering results from the literature. The heat transfer improved, the Nusselt number increased, and the electronic surface temperature decreased with an increase in the Vj/Vc ratio. However, the Nusselt number decreased with an increase in the H/D ratio. Models 2 and 4 had higher heat transfer from the electronic component than the other models. A low H/D ratio and low Vj/Vc ratio yielded higher heat transfer in Model 3 than in Model 1.

Measurement of thermal properties of liquid analytes using microfluidic resonators via photothermal modulation

Understanding the thermal properties of fluids at the nanoscale with high spatial, temporal, and thermal resolution are on great demand in the fields of MEMS, drug development, biomedical devices, and analytical systems. Microfluidic channel-integrated cantilevers are considered as an established benchtop sensor platform for physical and thermal characterization of materials at the picogram amount of analytes. This paper reports analysis of thermal characteristics of liquid analytes using photothermal heating effect of the microfluidic cantilever. Using real-time tracking of frequency shift of microfluidic resonator, the thermal properties of liquid samples can be estimated whilst the liquid analytes in the cantilever are locally heated by laser-induced irradiation. The heating results in the expansion of the liquid inside the channel which induces thermal stress on the walls of the channel. This thermal stress contributes to the rise of the resonance frequency of the microfluidic resonator and, therefore, the frequency shift is linearly dependent on the volumetric coefficient expansion of the liquid. A threefold improved sensitivity is observed when the second order flexural vibration mode is analyzed compared to that of the fundamental resonance. This approach, which combines photothermal heating and the dynamic mode of operation, can serve as a platform for the development of a portable, lab on a chip device for the use of real time detection of thermomechanical properties of fluids at low cost.

Numerical analysis of hydrodynamic and thermal characteristics of three inside channel configurations of a plate and shell heat exchanger (PSHE)

The Plate and Shell Heat Exchanger (PSHE) is a variation of the Plate Heat Exchanger (PHE) with a more compact and robust geometry. This paper presents the analysis of the flow in the inner channel formed by a pair of plates of a PSHE employing computational fluid dynamics to determine the hydrodynamic and thermal characteristics for three Chevron angle configurations, 15° × 15° (High/High-HH), 45° × 45° (Low/Low-LL) and 15° × 45° (High/Low-HL). The ANSYS CFX software was employed with the application of the Standard k-ε and the SST (Shear-Stress-Transport) turbulence models for comparison. Experimental pressure drop data and flow streamlines were used to validate the numerical model and to analyze simplifications in the geometric model. Pressure drop, friction factor, and Nusselt number were evaluated for the three geometries studied. A local analysis of the parameters that describe the channels was also performed in this study.

Effects of different tobacco materials on the release characteristics of aroma components

In order to reveal the release characteristics of different tobacco materials, the characteristics of tobacco materials and the release characteristics of smoke were analyzed. This paper studied 17 kinds of tobacco materials, the thermogravimetric analyzer was used to study the thermogravimetric characteristics of the tobacco materials, meanwhile the gas chromatography was used to analysis original aroma composition characteristics of the raw tobacco material, the smoke released from the pyrolysis of tobacco in a fixed bed reactor was also studied. The results showed: ① The elemental composition of different kinds of tobacco materials was similar, but there were significant differences in the volatile content (aroma components), among which the aroma components of tobacco stem were the highest. ②Different categories of tobacco raw materials have different properties of the aroma components. Among them, the nicotine content of roasted tobacco was higher, spice tobacco and tobacco stems mainly contain acid and ketone aroma components. However, burley tobacco and cigar tobacco are distinguished from other types of tobacco by the presence of aromatic substances such as new phytodiene.③ Through the analysis of thermal release characteristics of aroma components of different tobacco raw materials, it was found that the yield of aroma components was positively correlated with the volatile content of tobacco materials. The results of this study clarified the effects of different tobacco raw materials on the release characteristics of aroma components and provided theoretical guidance for the subsequent compound utilization of tobacco.

Effects of different tobacco materials on the release characteristics of aroma components

In order to reveal the release characteristics of different tobacco materials, the characteristics of tobacco materials and the release characteristics of smoke were analyzed. This paper studied 17 kinds of tobacco materials, the thermogravimetric analyzer was used to study the thermogravimetric characteristics of the tobacco materials, meanwhile the gas chromatography was used to analysis original aroma composition characteristics of the raw tobacco material, the smoke released from the pyrolysis of tobacco in a fixed bed reactor was also studied. The results showed: ① The elemental composition of different kinds of tobacco materials was similar, but there were significant differences in the volatile content (aroma components), among which the aroma components of tobacco stem were the highest. ②Different categories of tobacco raw materials have different properties of the aroma components. Among them, the nicotine content of roasted tobacco was higher, spice tobacco and tobacco stems mainly contain acid and ketone aroma components. However, burley tobacco and cigar tobacco are distinguished from other types of tobacco by the presence of aromatic substances such as new phytodiene.③ Through the analysis of thermal release characteristics of aroma components of different tobacco raw materials, it was found that the yield of aroma components was positively correlated with the volatile content of tobacco materials. The results of this study clarified the effects of different tobacco raw materials on the release characteristics of aroma components and provided theoretical guidance for the subsequent compound utilization of tobacco.

Thermal Coupling Simulation of Electro-Hydrostatic Actuator Subjected to Critical Temperature Conditions

Electro-hydrostatic actuators (EHAs) are emerging transmission techniques originated from aerospace industry and being introduced to various application fields, such as ships, robots, construction machines, and machine tools. Despite the advantages of high efficiency, easy maintenance, electrified power, etc., EHAs are usually self-contained integrated devices, resulting in low heat dissipation ability. Therefore, thermal coupling models are necessary for the evaluation of each design option during the EHA development. In this paper, a thermal coupling model was established for EHA thermal characteristic analysis during the detail design stage. The disciplines of electrics, mechanics, system level hydraulics, losses, and control are implemented by lumped parameter modeling while the disciplines of thermodynamics and fluid dynamics are simulated by computational fluid dynamics (CFD). Subsequently, a simulation analysis focusing on the critical temperature conditions was conducted, and the dynamic thermal and power responses were achieved. The simulation results are applicable to gain confidence for EHA detail design work as well as proved the functions of the proposed model as a practical development tool.

Experimental Analysis of Mechanical and Thermal Characteristics of Luffa/Epoxy Polymer Composite under the Influence of Nanosilica

In the current work, the experimentations have been accomplished to assess the impact of diffusing nanosilica particles in epoxy matrix on the mechanical and thermal performance of the luffa fibre reinforced epoxy composite material. The matrix and fibre composition are fixed as 80 : 20 throughout the study, and the nanosilica is disbanded in diversified volume fractions of 0%, 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%, respectively, while preparing luffa/epoxy/nanosilica (LES) composite samples. The mechanical characteristics, such as tensile, flexural, and impact behaviour of the composite, and the thermal properties, namely, thermal stability and thermal conductivity, are examined for the LES samples. The experiments are accomplished as per the ASTM standards. The results revealed that the assimilation of nanosilica particles in epoxy has improved the mechanical and thermal characteristics of the composite significantly. The tensile, flexural, and impact strength of the composite have been amended by 157.58%, 66.9%, and 16.5% with 1.5% addition of nanosilica in epoxy. Similarly, thermal conductivity of the composite is improved by 47.53% with the dispersion of 2.5% nanosilica in epoxy matrix. In addition, the thermal stability of the LES composite samples is substantially improved while disbanding nanosilica in epoxy matrix. However, the better results are reported for the LES composites containing 1.5% nanosilica content, compared to the next higher volume fractions of nanosilica content in epoxy matrix.

Optimization and Control for Solid Oxide Fuel Cell System Hybrid DC Microgrids From the Perspective of High Efficiency, Thermal Safety, and Transient Response

Managing the power transients with both high efficiency and thermal management constraints is a difficult task in the solid oxide fuel cell (SOFC) hybrid direct-current (DC) microgrids. This article proposed a SOFC-based DC microgrid, which consists of the SOFC stand-alone system, DC microgrid network, and DC/DC boost converter, along with the associated DC/DC load. The control and optimization strategy of the SOFC-based DC microgrids has been designed, including the thermal and electrical characteristics analysis. First, the voltage and current regulator based on the proportional–integral (PI) is designed, which can maintain the voltage stability of the proposed SOFC system. In addition, the optimal regulator based on the optimal operating points (OOPs) is designed, which can realize high efficiency and steady-state thermal safety of the proposed SOFC system. Finally, the main performance, including the SOFC stack electrical characteristics verification, SOFC stand-alone system electrical and thermal response, load-tracking characteristics, and system efficiency is observed and discussed in the proposed control and optimization strategy. Experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed optimization and control strategy.

Maximizing Self-Supervision From Thermal Image for Effective Self-Supervised Learning of Depth and Ego-Motion

Recently, self-supervised learning of depth and ego-motion from thermal images shows strong robustness and reliability under challenging scenarios. However, the inherent thermal image properties such as weak contrast, blurry edges, and noise hinder to generate effective self-supervision from thermal images. Therefore, most research relies on additional self-supervision sources such as well-lit RGB images, generative models, and Lidar information. In this letter, we conduct an in-depth analysis of thermal image characteristics that degenerates self-supervision from thermal images. Based on the analysis, we propose an effective thermal image mapping method that significantly increases image information, such as overall structure, contrast, and details, while preserving temporal consistency. The proposed method shows outperformed depth and pose results than previous state-of-the-art networks without leveraging additional RGB guidance.

A comprehensive analysis and experimental investigation for the thermal management of cell-to-pack battery system

Driving range has become one of the primary issues restricting the electric vehicle development, which requires more battery energy to be filled in the pack volume. However, it is challenging to continuously to enhance the specific energy of battery. Compact pack structure can further enhance the specific energy of the pack, such as the cell-to-pack (CTP) design. Compared with the traditional design structure, the CTP battery system omitted the small module components, which directly increased the volume energy density by 15%-20%, making an essential breakthrough in pack specific energy. The thermal performance of the CTP battery pack gradually emerged in applications. Thermal performance analysis for the CTP battery system has become a critical factor restricting the large-scale application. This paper carries out the primary work is for the digital twin modeling of the CTP battery system. An accurate thermal model of cells and the battery pack with a liquid plate structure is established based on measuring the heating characteristics and thermo-physical parameters. After calibration, the thermal model can not only predict the temperature response of CTP system under fast charging and cooling conditions, but also further guide the development of other battery systems. The calculation error of the CTP thermal model is controlled within ± 15% under various operations compared with the experimental results. The proposed thermal model synchronizes with the battery pack test, significantly enhances the efficiency of battery system design, providing guidance for the thermal characteristics analysis, design, and optimization of CTP pack thermal management systems.

Analysis of Thermal Characteristics of MEMS Sensors for Measuring the Rolling Period of Maritime Autonomous Surface Ships

Recently, with the emergence of maritime autonomous surface ships (MASS), ensuring seaworthiness has increased with the operation of MASS. Ship stability is important for safety, and technical methods for controlling a ship’s motion are required to evaluate the stability. A ship’s rolling period is estimated using microelectromechanical systems (MEMS) sensors to measure the ship’s metacentric height. However, weather changes (e.g., temperature) are drastic due to various marine environments in the sea. Hence, it is necessary to analyze MEMS sensors’ thermal characteristics for applying them to MASS. This study aims to analyze the thermal characteristics of a siX-axis MEMS sensor for its application in MASS. The experiments analyzed measurement errors and noise at six steps in the range of 25–75 °C in which the MEMS sensor can be operated. The experimental results showed that the gyroscope’s thermal error and MEMS sensor’s noise level were much larger than those of the accelerometer and the respective thermal error values along the Z-axis of the accelerometer and gyroscope were the most stable compared to those along the other axes. The findings can be applied to a measurement method of the stability of MASS employing MEMS sensors in navigation equipment.

A comparative study on harmonic analysis and thermal performance of different types of lamps for residential building

This paper investigates the analysis and study of power quality, harmonics and thermal characteristics of halogen lamps, compact fluorescent lamps (CFLs) and light emitting diode lamps (LEDs). As nonlinear loads, CFLs and LEDs produce highly distorted currents compared to halogen lamps. The harmonic absorptions of each individual tested lamp are analyzed. Then, measurements with different groups of LEDs are conducted to investigate the effects of diversity factors. Although LEDs produce considerable amount of harmonics, it is concluded that amount of harmonics can be reduced by combining various types of LEDs. In addition, it could be observed that as the number of lamps increases, the diversity factor decreases. Finally, the thermal characteristics of lamps are compared in this paper. Results show that LEDs produce less heat compared to halogen lamps and CFLs.

Surface Heat Flow, Deep Formation Temperature, and Lithospheric Thickness of the Different Tectonic Units in Tarim Basin, Western China

Abstract Herein, the new collected well-testing temperature as well as continuous steady-state temperature logs were achieved for the analysis of deep thermal structural characteristics and current thermal states of various tectonic units in Tarim Basin. Generally, geothermal gradient fluctuates in 14.6-31.1°C/km, the heat flow ranges between 31.6 and 59.2 mW/m2 with the average heat flow of 43.2 mW/m2, and these values are typical of low heat flow background in Precambrian craton basins. Furthermore, estimated formation temperature spatial distributions at 6~8 km depth are the same and are mainly under the control of basement structural pattern. At 6000 m depth, temperature is 99-188°C, which become 126-242°C and 113-215°C at 7000 m and 8000 m depths, respectively. These findings confirmed that heat flow in Tarim Basin was relatively low with similar geothermal regimes to other Precambrian craton basins around the globe. In addition, 1D theoretical crustal thermal structures in Tarim Basin were established based on the solution of the equation of steady-state heat conduction. The findings revealed that “thermal” lithosphere maximum thickness in Tarim Basin is witnessed in Manjiaer sag. Tazhong uplift thermal state differs from those of Tabei uplift and Manjiaer sag. Tazhong mantle heat flow is 23.9 mW/m2, which accounts for 48.8% of surface heat flow. Hotter thermal states of Tazhong uplift generated temperatures as high as ∼690°C in Moho. Tarim Basin heat flow distribution reveals that crustal heat flow plays a more significant role in surface heat flow and possesses typical “hot crust and cold mantle” model thermal structure properties.

Analysis of Thermal Characteristics and Electrical Signal Using a Damaged Multi-outlet

Recently, the use of multi-outlets has been increasing owing to the increased use of electrical appliances in households. The majority of users do not replace multi-outlets for several months or even years after purchase. Moreover, with the intention to save energy and prevent fire, users frequently unplug electrical appliances from multi-outlets, which may cause structural defects. Owing to a poor connection between the multi-outlet and plug, there is a risk of generating local heat, which may lead to fire. Therefore, in this study, a damaged multi-outlet with structural defects owing to long-term use is secured through repeated tests, and the risk of fire is determined based on its thermal characteristics and electrical current generated during use. It was confirmed that the temperature of the main switch was higher than that of the plug connection, and the damaged multi-outlet temperature was up to 2.4-fold higher than normal.

Thermal Characteristic Analysis of Sodium in Diluted Oxygen via Thermogravimetric Approach

As the main reactor type of the fourth-generation nuclear power systems, sodium-cooled fast reactors are now designed and built worldwide. A sodium pool cooling circulation process is indispensable in a sodium-cooled fast reactor. However, the sodium pool fire design is the basis of accidents in sodium-cooled fast reactors. The fire hazard caused by the sodium–oxygen reaction and fast reactor safety have attracted extensive attention. Dry powder is widely used as an effective fire-extinguishing agent to control sodium fire. The sodium will burn in an oxygen-depleted atmosphere when using dry powder to cover fire. In this study, the change law of thermogravimetry of melted sodium is studied by thermogravimetric analysis (TGA) and the apparent activation energy (Ea) is obtained, which has a linear relationship with the oxygen concentration. The results can provide a reference for improving the engineering design standards of sodium fire suppression systems and can also be incorporated into simulation software to improve the accuracy of fire suppression simulations.

ANA LYSIS OF THE FLOW AND THERMAL FIELDS IN BOBTAIL ROOFS HEATED FROM THE BASE WALL

Analysis of airflow and thermal characteristics of attics of bobtail-shaped pitched roofs heated through a horizontally suspended ceiling is numerically carried out in this study. Pitch angles of 14o, 18o, 30o, and 45o within the standard pitch roof range are selected. The configuration falls within Rayleigh number 3.19 x 105  Ra  2.04 x 107. A finite-volume CFD code was used to solve the mass, momentum, and energy conservation equations governing the problem. The results obtained indicate a strong influence on the shape and angle of the roof. At lower roof pitches, the flow field is characterized by multiple counter-rotating vortices asymmetrically arranged within the enclosures. Eight cells in the 14o enclosure were reduced to five in the 45o roof pitch. The size and rotating strength of a vortex increase from the left corner to the middle of the enclosures. At higher pitch angles, the vertical wall obstructed the flow leading to a number of distorted cells. The maximum velocity within the aerodynamic boundary layer along the base wall occurs at Y=0.02 with the values U=0.013 and U=0.028 in the 14o and 45o enclosures respectively. The thermal field portrays a convection system of rising hot plumes from the base wall and descending cold jets from the inclined walls; all enclosed by thin boundary layers along the walls. Graphical plots of velocity and temperature variations along some cross-sections within the enclosures enable the prediction of some important heat and flow parameters.

Experimental investigation of different-shaped microwave-heated potatoes: thermal and quality characteristics analysis for food preservation.

Food materials are consumed for nutritional purposes in the form of fruits, vegetables, plants, and meat. These contain proteins, carbohydrates, and other useful nutritional compounds and these processed foods are a rich source of nutrition. The demand and supply of hygienic food for a particular population is possible only by food preservation. It can be done by various methods such as drying, freezing, chilling, chemical preservation, and pasteurization. Drying is a method of food preservation and it can be done by solar drying, microwave heating, vacuum drying, and some other methods. Microwave heating is a fast-drying method. It utilizes electrical energy to generate heat energy. The domestic microwave oven is not harmful but a commercial-level oven may be little bit harmful, when operated on high frequency. Potato is used as a sample material with different shapes such as slab, cylindrical, and spherical. The microwave oven has been operated at four different microwave powers such as 100W, 300W, 600W, and 800W. Slab-shaped (30°C), cylindrical-shaped (31.5°C), and spherical-shaped (30.5°C) food materials achieved maximum temperatures of 83.9°C, 110.6°C, and 146.1°C respectively. The temperature variations and drying characteristics of the food samples have been monitored. An oven has achieved maximum drying efficiency of 25.65% with a slab-shaped sample. For the detection of the cracks and chemical compositions in the food samples, SEM with EDS analysis has been performed. Economic analysis of microwave oven has also been done and payback period has been found as 3.27years.

Analysis of Flow and Thermal Characteristics in a Rectangular Chamber with a Hollow Cylinder Under a Horizontal Turbulent Buoyant Jet

Analysis of Flow and Thermal Characteristics in a Rectangular Chamber with a Hollow Cylinder Under a Horizontal Turbulent Buoyant Jet