Thermal Module Research Articles

The research of a multi-stage roller type magnetorheological transmission device on temperature properties

Magnetorheological Transmission Device (MRTD) is a controllable power regulation device using magnetorheological fluid as the transmission medium. It has characteristics of fast response, a wide range of speed regulations, and a pollution-free environment. The traditional pairwise transmission structure has serious heat generation problems during operation, resulting in low transmission efficiency. Therefore, we innovatively propose a multi-stage roller type MRTD to improve the heat generation problem fundamentally. The steady-state and transient temperature fields of the multi-stage roller type MRTD are simulated using the thermal analysis module in ANSYS based on the temperature field formulation. The variations of internal temperature at different slip powers are obtained. The results show that the designed multi-stage roller type MRTD has a good suppression of temperature rise. This study can provide a new approach to improve the thermal performance of MRTD.

Design and analysis of cooling jacket developed for vacuum power tubes by multiphase cooling

The vacuum tubes are used extensively in electronic industries. The MW level of vacuum tube are used in RF amplifiers and microwave sources in different sectors like defence, nuclear energy, satellites and medical diagnostics. The first step in the indigenous development of MW level of vacuum tube is the design of its cooling jacket. The cooling jacket of vacuum tubes use hypervapotron (HV) fins which are known for providing efficient cooling in compact space. The key objectives of this paper are to finalize the jacket’s construction material, evaluate the cooling jacket’s heat transfer performance at the MW level of RF (radiofrequency) power, and forecast safe operating conditions for given conditions of high heat flux and water flow rates. In this design, the vacuum tubes’ external dimensions are taken into consideration when designing the cooling jacket. ETP copper (Electrolytic Tough Pitch copper) and copper-chromium-zirconium (CuCrZr) are likely materials for the jacket’s construction. For the aforementioned design of the cooling jacket, FEA (Finite Element Analysis) simulations using a steady-state thermal module and computational fluid dynamics (CFD) simulations using an ANSYS CFX module are described for flow rates of 15, 30, and 60 lpm (liters per minute) and the heat flux 1, 2, 4, and 6 MW m−2. The results of CFD and FEA simulations are found to be in close agreement. A small deviation in results is seen after the start of nucleate boiling. 30 and 60 lpm are desirable flow rates for high heat flux values greater than 2 MW m−2. CuCrZr is the ideal material for a cooling jacket’s construction as it has safe working temperature limit of 350 °C at high heat flux values. Also, 15 lpm flow rate should be avoided while using this cooling jacket at heat flux values greater than or equal to 6 MW m−2.

Machinability improvement of titanium alloys in ultra-precision machining with micro-structured surface

Titanium alloys get wider applications in different areas due to its excellent mechanical properties. However, poor thermal conductivity and low elastic module of titanium alloy induce high tool wear and make it being one of hard-to-machine materials; especially the segmented chip formation accelerates the diamond tool wear in ultra-precision machining (UPM) of precision parts. This study applies micro-structured surface to improve machinability of titanium alloys in UPM by reducing the chip segmentation induced cutting forces fluctuations. Finite element (FE) model is built to study chip formation mechanism and characterize geometries of segmented chips in orthogonal diamond cutting of Ti6Al4V alloy with the aims at the design of micro-structures array. Turning experiments are conducted to compare cutting force, surface roughness, and tool wear for diamond turning of Ti6Al4V alloy on smooth surface and micro-structured surface. The results show that the FE simulated saw chips agree well with the measured ones. Moreover, the micro-structured surface helps to decrease cutting force, reduce diamond tool wear, and improve surface quality for UPM of titanium alloy. Especially, the new method fabricates micro-grooves array on the machined surface in half-finishing process of UPM without the need of any material pre-processing and extra manufacturing equipment, which can also provide the guidance for efficient and sustainable UPM of titanium alloys parts with high surface quality.

Comprehensive analyses of solar thermal module with booster mirror integration for adaptation to various application scenarios

Integration of a booster mirror reflector enhances the performance of evacuated tube collector within a prescribed range of solar incidence angles and reject solar rays within others. Seasonal performance adjustment makes it possible to adapt to various scenarios with different seasonal application purposes, for example, only domestic hot water, only space heating, or both. In this study, a mathematical model describing the photo-thermal conversion of this solar module was developed and validated using experimental data. The dynamic contributions of the collector and mirror planes were decomposed, and the optimal combination configurations for adaptation to three different application scenarios in four representative Chinese cities were investigated through the rotation of both planes. The three scenarios were: Scenario 1, annual performance augmentation; Scenario 2, coldest month performance augmentation; and Scenario 3, winter performance augmentation and prevention of summer overheating. It was found that optimal performance was always achieved when the collector plane was perpendicular to the mirror plane in the three scenarios. Depending on the optimal configurations, in Scenario 1 the mirror reflector contributed 30–32% heat energy, in Scenario 2 the mirror reflector contributed 41–49% heat energy during the coldest months, and in Scenario 3 the mirror reflector contributed 40–47% heat energy during the entire heating season. The objective of this study was to develop a comprehensive tool to evaluate the photo-thermal performance of this solar module and determine optimal configurations for various application scenarios.

CGINet: Cross-modality grade interaction network for RGB-T crowd counting

Crowd counting is a fundamental and challenging task that requires rich information to generate a pixel-level crowd density map. Additionally, the development of thermal sensing and its applicability to computer vision has enabled the use of thermal information for crowd counting. Considering the complementary characteristics of RGB (red–green–blue) and thermal images in different feature encoding stages, we propose a cross-modality grade interaction network (CGINet) for RGB-T (RGB and thermal) crowd counting. We introduce an RGB cooperative enhancement module for thermal information to correctly extract low-level features from scenes containing objects with different scales. As RGB information is sensitive to lighting and occlusion while extracting high-level features, we propose a thermal information supplementary module to increase the RGB feature robustness. In addition, a novel multilayer decoding module fully integrates features at different levels, exploits the features of different layers, and predicts the crowd density map. Results from comprehensive experiments on the RGBT-CC benchmark demonstrate the effectiveness of the proposed CGINet for RGB-T crowd counting. In addition, CGINet achieves excellent results on the ShanghaiTechRGB dataset containing paired RGB images and depth maps. The experimental results highlight the advanced architecture and generalization ability of CGINet for multimodality crowd counting.

Energy, economic, and environmental evaluation of a solar-assisted heat pump integrated with photovoltaic thermal modules using low-GWP refrigerants

Solar-assisted heat pumps integrated with photovoltaic thermal modules (PVT-HPs) have been extensively studied owing to their superior heating performance. However, the investigation of PVT-HPs using low global warming potential (GWP) refrigerants to replace R134a is required to comply with environmental regulations. This study aimed to investigate the substitutability of R1234yf, R1234ze(E), and R152a in PVT-HPs based on energy, economic, and environmental analyses. The heating performance of heat pumps using these low-GWP refrigerants was measured. Furthermore, transient simulations were performed using transient system simulation software to determine the annual performance of the PVT-HPs using low-GWP refrigerants. Based on the simulation results, the levelized cost of energy (LCOE) and Specific Life Cycle Climate Performance (SLCCP) were evaluated. R152a was the most economical refrigerant, showing a 50% reduction in LCOE compared to R134a because of its lower electricity purchase cost and higher sale cost. Furthermore, the SLCCPs of PVT-HPs using R1234yf, R1234ze(E), and R152a decreased by 16.8%, 17.5%, and 20.8%, respectively, compared to those using R134a. Accordingly, the refrigerant substitutability index of R152a was the highest at 1.431, owing to its superior economic and environmental performance. In conclusion, only R152a was deemed appropriate for replacing R134a in PVT-HPs.

SIMULATION OF FLOW AND HEAT EXCHANGE IN A HEAT ACCUMULATOR TANK

The article deals with the research of thermal energy storage tanks. It is proposed to use a «thermal core» to minimize the effects of thermal stratification and high thermal inertia. The thermal core consists of a binary tube placed along the central axis of the tank, filled with a paraffin mixture with a melting point of 45 to 65oC and a density of 0,880 to 0,915g/cm3 at 15oC. In the study the Fluent software package was used to model the temperature distribution in the tank under free convection conditions, the data was then converted to the Transient Thermal module of the ANSYS software package for further calculations of the unsteady temperature distribution in the thermal core. The study showed that a 1400-liter thermal energy storage device, heated for 1 hour by a heat-transfer fluid at 115oC, cools down to 50oC in 4 hours. The research also revealed the need to improve the tank design based on the analysis of the hydrodynamic structure of the flow in the tank, as evidenced by the trajectory distribution of free convective flows. The authors concluded that the use of a heat core, regardless of the type of paraffin used to form it, helps to reduce temperature stratification by height in the tank and that the type of paraffin used has no significant effect on the overall cooling of the tank. However, using ceresin as a core filler results in a slightly higher average tank temperature. Based on the results of the study, the time of complete cooling of the tank was determined by the non-uniform temperature field of all elements of the tank.

Thermal Effusivity Tester (TET)—A New Device to Determine Thermal Effusivity of Textiles

Thermal effusivity tester (TET) is a new device to measure the thermal conductivity and the thermal effusivity (heat dissipation) of textiles under a defined compression, developed at the R&D department of Lenzing AG (Austria). The device performance was tested by comparing its results with results from commercially available devices Alambeta, TCi Thermal Conductivity Analyzer and Kawabata KES-f thermal module. The fabrics tested were typical knit and weave constructions made of different fiber types, including cotton, wood-based cellulosics and polyester. For most of the fabrics, thermal effusivity results show wide agreement among TET, Alambeta and TCi, and strong positive correlation (r > 0.82) with heat flow (Qmax) as obtained from KES. Deviations were observed for some thicker and more resilient fabrics, most probably caused by the differences in the pressure applied by the devices on the fabric surface. The results show that TET offers a reliable and experimentally flexible approach to assessing thermal effusivity on textile structures and emphasizing the role of the dimensional change induced by the measurement conditions on the measured thermal effusivity and conductivity.

A Review of Sensor Applications in Electric Vehicle Thermal Management Systems

With the rapid development of the automotive industry, the application of sensors is of great importance in maintaining the reliability of electric vehicles and ensuring the safe operation of electric vehicles. Faced with the increasing data of thermal management system condition monitoring, sensor detection is widely used in the monitoring of electric vehicle thermal management system. In recent years, a large number of related studies and contributions to the literature have been published. Although a number of reviews have summarized this, these reviews lack an overview of the issues and methods raised in these studies. This paper reviews recent sensor applications for electric vehicle thermal management systems. Currently, battery internal sensors, battery external sensors and related multi-sensor fusion, traditional motor sensors, positionless motor sensors, and component-level sensors of air conditioning systems are the main application sensors in the field of thermal management systems. This article introduces the basic principles of each type of sensor, reviews the relevant applications of various thermal management modules, and summarizes the usage characteristics of each type of sensor. The main problems faced by the existing research on the application of thermal management system-based sensors, such as the detection accuracy of traditional sensors and the detection stability of advanced sensors, are summarized, and the solutions proposed by the existing research are also summarized. Finally, some future research directions, trends, and hotspots are outlined. It is hoped that this review can help readers to understand the problems and existing solutions for thermal-management-system-based sensor applications, and to conduct related research more effectively.

Моделирование теплоэлектрических процессов в силовых модулях на MOSFET-транзисторах

The paper represents thermal model of power MOSFET module based on a transistors mounted on copper-ceramic DBC (Direct Bond Copper) plate. The analysis of thermal processes in the module caused by pulse heating of particular transistors was performed by the finite elements method using COMSOL Multiphysics. The model performs estimation of the temperature field on the DBC plate and transistors overheat temperature. The modeling results was compared to the experiment – thermal impedance matrix measured by the modulation method using the heating power modulated by the harmonic law. Analysis of the data obtained allows to conclude that the calculated and experimental values of the dies overheating temperature are in good agreement with each other and confirms the correctness of the developed thermal power module model

Parameter prediction optimization of data center’s heat dissipation system using machine learning algorithms

In this study, an optimization control method based on knowledge and operational data was investigated for a centralized water-cooling heat dissipation system in a data center. First, a numerical model describing the heat transfer and thermodynamic processes of the heat dissipation system was established, and five thermal characteristic parameters were extracted to identify the system. The thermal characteristic parameters, used as inputs to the model, were identified in real time using the mechanism formula from the operational data. Subsequently, the operational data of the heat dissipation system in a real data center were used to validate the numerical model. The model accuracy was within 15 %. The water flow rate of the actual system was optimized, showing that the average PUE of four typical cases under the optimized conditions were 1.12, 1.25, 1.13 and 1.3, respectively, with an improving rate between 4.3 % and 12.4 %. Next, considering the reasonable value ranges of the five thermal characteristic parameters and four direct input parameters, 62,208 groups of working conditions were designed, and the optimized water flow rate and the corresponding COP and PUE for each working condition were obtained using the numerical model. Finally, a prediction model that combined the heat transfer mechanisms was established based on an optimized dataset. Machine learning algorithms were applied to establish neural networks between the nine inputs and three optimized operating parameters. Based on the prediction model and thermal characteristic parameter identification module, software was developed to suggest optimized water flow rates and predict the PUE and COP in real time from the operational data.

Study on effective front region thickness of PCM in thermal energy storage using a novel semi-theoretical model

Thermal energy storage in mobile applications, particularly battery of electric vehicles, is currently gaining a lot of importance. In this paper, a semi-theoretical time-dependent mathematical model of the phase change in a double shell thermal energy storage module has been developed where the inner tube is a heat exchange surface. An effective front region thickness for the melting and solidification process has been studied. The proposed model is calibrated based on our experimental data. The purpose of such a model is to enable the optimization of the geometry of the energy storage modules in terms of the PCM to the TES container mass ratio and enhancement of phase change rate. In addition, results obtained for a single tube can be used in the bundle of tubes in shell and tube TES design. The results have shown that for the larger diameter of the module (smaller difference between the working tube and shell diameter) the optimal working time is around 2000 s.

Infrared image enhancement algorithm based on improved wavelet threshold function and weighted guided filtering

Aiming at the problems such as the poor visual effect of infrared thermal imaging under low illumination conditions, an enhanced infrared image recognition method based on wavelet decomposition is proposed for this paper. First, according to wavelet decomposition, the infrared image is divided into a low-frequency sub-band (LFS) and high-frequency sub-band (HFS) in each orientation, and HFS in each orientation is denoised using a modified wavelet threshold function to strengthen the denoising effect of the infrared image; Second, the multi-scale Retinex (MSR) algorithm based on weighted guided filtering (WGIF) is used to evaluate the component of illumination in the basic layer of the LFS, and the WGIF-segmented detail layer images are fused with the MSR processed ones to effectively highlight the texture details of the LFS; Finally, the LFS and the HFS are wavelets reconstructed (WR) to obtain the infrared enhanced images. This paper applies the algorithm to a low-resolution (resolution 32x32 pixels) infrared thermal imaging module, and the results of combining subjective and objective evaluation indexes show that the overall property index of the algorithm in this paper is superior to other contrasting algorithms and can effectively improve the infrared image quality.

Modeling and analysis of thermal photovoltaic energy generator using COMSOL multiphysics

Because of to their versatile energy choice alternatives, immovable elements, and opportunity for effective energy generation, thermophotovoltaic techniques have a vast range of achievable applications. For illustration, these devices could help us to offer convenient energy. Nevertheless, first enhance the performance of thermo-photovoltaic cell unit devices along with decrease system costs and system temperatures. To achieve such objectives, we use simulation to evaluate and improve their thermo-photovoltaic cell unit models. This research regarded as the different alternatives of enhancing system operation via successful deal with the operating circumstances. It examined solutions of the system formation for much better system performance and energy output and at bare minimum quantity working expenses. The number of mirrors and photovoltaic devices for employ in the construction had been set at eight as traditional for the procedure. A novel energy technique was constructed and was used to reproduce the energy effectiveness of the thermal photo voltaic modules. The boundaries situations utilized for the materials involved were defined and the appropriate physics utilized in the analysis of various operating circumstances that affected the system effectiveness. It is possible to reduce the costs of PV systems by using small area PV cells, which require some special mirrors to focus radiation onto photocells. Based on COMSOL Multiphysics (version 5.5) as a commercial FEM package, this paper develops a basic thermo-photovoltaic cell unit model. A variety of options examined for optimizing the operation of the system by controlling operating conditions effectively. For a two-dimensional system, it was demonstrated the correct physics to apply when studying various operating conditions which affected system performance.

Energy and stress analysis of a hybrid photovoltaic thermal module

Photovoltaic (PV) solar panel systems are widely used for meeting domestic electricity requirements because of their simple and cost-effective operation. It is well known that the electrical efficiency of PV panels is abruptly disturbed by cell temperature which depends upon several factors, including ambient temperature. In this study, the increased electrical efficiency of a PV module has been demonstrated by integrating a water storage tank at the backside of the PV module turning the simple PV module into hybrid Photovoltaic Thermal (PVT) module. The water tank acts as the reservoir and provides water flow at the backside of the PV module and the temperature difference between water and cell causes the heat exchange between the back surface of the PV panel and water, resulting in the lowering of the PV module cell temperature. This hybrid design has resulted in a 19% increment in the electrical efficiency of the PV panel. The system is designed to store hot water at 40 °C. In addition, a PVT thermal efficiency of 36.5% is also achieved which can be used to meet hot water domestic applications. The structural analysis of the system design through ANSYS® is also carried out to determine the effects of water pressure on the tank and it has been found that the design is safe and secure.

Actively-exploring thermography-enabled autonomous robotic system for detecting and registering HVAC thermal leaks

The inefficiency, labor-intensity, and possibility of automation of the current practice of HVAC system inspections, which heavily relies on human inspectors, are being questioned. This paper describes a lightweight and reproducible robotic system dubbed AcTEA-bot, that automatically detects and locates thermal leaks in ceiling environments while self-navigating. AcTEA-bot is designed and built upon three modules, including an active visual SLAM module, a thermal leak detection module, and a thermal leak registration module. To evaluate the effectiveness of AcTEA-bot, a true-to-scale ceiling environment containing five thermal leaks is built, and 30 experiments are conducted where AcTEA-bot starts with different poses and conducts the inspection task. Results demonstrate that thermal leaks of multiple types in ceiling environments can be accurately detected and located.

Effect of mechanical vibration on phase change material based thermal management system for a cylindrical lithium-ion battery at high ambient temperature and high discharge rate

The performance and safety of lithium-ion batteries (LIB) in electric vehicles (EV) depend strongly on the operating temperature, so an effective battery thermal management system (BTMS) is essential. Battery thermal management (BTM) technology based on phase change material (PCM) is currently considered to be one of the most promising approaches. Electric vehicles are inevitably affected by vibration during operation, and many studies have shown that mechanical vibration can enhance natural convection heat transfer. The effect of mechanical vibration on the PCM-based battery thermal management module of a single cylindrical lithium-ion battery at high ambient temperature and high discharge rate is studied by numerical simulation for the first time in this paper. N-octadecane is selected as the PCM application in the cylindrical battery's periphery. The results show that: (1) mechanical vibration enhances the heat transfer of natural convection to limit the excessive temperature rise and improve temperature uniformity of the lithium-ion battery, and when the PCM is 12 mm, the mechanical vibration has the most significant impact on the PCM-based BTMS (2) when the vibration frequency is 10 Hz, the cooling effect of the battery thermal management module is the best, which is 28.05% lower than when there is no vibration. when the vibration frequency is 50 Hz, the temperature uniformity of the battery is the best, with a maximum temperature difference of 3.86 K. (3) when the vibration amplitude is 100 mm, the maximum temperature difference of the battery is 1.89 K, and the maximum temperature decreases by 27.74%. This study provides a new perspective for the thermal management system of lithium-ion batteries for electric vehicles.

Field studies of a thermoelectric system for thermal action on the anterior segment of the human eyeball

Objective. The aim of the study is to develop the design of a thermoelectric system (TPS) for thermal action on the anterior segment of the human eyeball, as well as to conduct its field studies.Method. The study is based on the methods of thermodynamic analysis, natural and computational modeling of processes and life support facilities.Result. The design of TPP for thermal impact on the anterior segment of the human eyeball is presented. Its fullscale studies were carried out in accordance with the existing methods of thermophysical measurements. Curves of changes in the temperature of the surface of the gelatin model of the human eyeball over time during cooling and heating were obtained for the supply currents of the thermoelectric module (TEM) included in the TPP, equal to 2.5 A, 3 A, 3.5 A, A and 1 A, 1 .2 A, 1.4 A, as well as changes in the temperature of the object of influence over time when changing the cooling mode to heating and vice versa. To assess the possibilities of heat removal from the hot junctions of TEMs in the system, data were obtained on the change in their temperature over time during the cooling effect for various values of the module supply current.Conclusion. It has been established that standard modules produced by domestic firms can be used as TEMs in the system. The duration of entering the TPP mode is about 230 s. The refore, it seems appropriate to bring the TPP to the operating mode before the actual procedures are carried out. It has been established that the duration of TPP switching from cooling to heating mode and vice versa is 230 s, which requires further optimization of the design and operating modes of the device through the use of more advanced types of TEMs and the use of forced operation of thermal modules in the transient mode.

Метод определения коэффициента эффективной теплопроводности пористого материала на основе минимальной поверхности типа Schoen’s I-WP(R)

Currently, to develop the materials with predictable properties at the macrostructural level, triply periodic minimum surfaces (TPMS) are used. The production of materials with an ordered structure of TPMS has become available due to the active development of additive technologies. Such materials have high strength-weight ratio, which is important in many structural problems. The study of the thermophysical properties of materials is necessary for the further design of various types of thermal insulation, heat exchangers, etc. In this regard, the study of the thermophysical properties of materials with an ordered structure based on TPMS is a topical issue. The paper proposes to study the thermophysical properties of materials with an ordered structure of Schoen’s I-WP(R) TPMS. Using the ANSYS software package (Steady-State Thermal module), numerical simulation of the heat transfer process in the material under study is carried out. The study is carried out for a material common in additive technologies, that is PETG plastic. The article presents the results of a study of the thermophysical properties of a material with an ordered macrostructure based on Schoen’s I-WP(R) triply periodic minimal energy surfaces. Based on the simulation results, graphical and analytical dependences of the heat flux density and effective thermal conductivity of the material are obtained. The results of the heat flux density are obtained in different directions with variable geometric parameters of the structure (the thickness of the cell wall and the length of the edge of the cube in which the cell is inscribed). Using the ANSYS software package, numerical simulation of the heat transfer process in the material under study is performed. The calculation results show a linear dependence of the effective thermal conductivity of the homogenized material on the wall thickness of the unit cell. It is shown that the intensity of heat transfer depends not only on the wall thickness and unit cell size, but also on the direction of the heat flux. The obtained results of the study can be used to create materials with predictable thermal conductivity by changing the dimensions (cell wall thickness and cube edge length) and high strength-weight ratio. The production of the material is possible with the help of additive technologies.

State of Charge and State of Health Estimation of Lithium-Ion Battery Packs With Inconsistent Internal Parameters Using Dual Extended Kalman Filter

Abstract The internal battery parameters of the lithium-ion battery energy storage system may be inconsistent due to different aging degrees during the operation, and the thermal effect can also threaten the safety of the system. In this paper, based on the second-order resistor–capacitor equivalent circuit model and the dual extended Kalman filter (DEKF) algorithm, an electrical simulation model of a LIB pack with inconsistent parameters considering the thermal effect is established, in which state of charge (SOC) and state of health (SOH) are estimated using DEKF, while the temperature is calculated by a thermal module. The simulation results show that the DEKF algorithm has a good effect on battery state and parameter estimation, with the root-mean-square error of voltage is lower than 0.01 V and SOC mean absolute error (MAE) is below 1.50%, while SOH error is 3.37%. In addition, the thermal module can provide an accurate estimation of the inconsistent temperature rise of the battery pack, and the MAE between the model-calculated temperature and the experiment is no more than 6.60%. The results provide the basic data for the scale-up of the electrothermal co-simulation model of the LIB energy storage system.