Heat Dissipation Conditions Research Articles

A Net Shape Profile Extraction Approach for Exploring the Forming Appearance of Inclined Thick-Walled Structures by Wire Arc Additive Manufacturing

Wire arc additive manufacturing (WAAM) offers a viable solution for fabricating large-scale metallic parts, which contain various forms of inclined thick-walled structure. Due to the variety of heat dissipation conditions at different positions, the inclined thick-walled structure is a major challenge in fabrication that may produce collapses and defects. However, there is a lack of effective sensing method for acquiring the forming appearance of individual beads in the structure. This paper proposes a novel approach for extracting individual bead profiles during the WAAM process. The approach utilizes a structured-laser sensor to capture the morphology of the surface before and after deposition, thereby enabling an accurate acquisition of the bead profile by integrating the laser stripes. Utilizing the proposed approach, the research investigated the forming mechanism of beads in inclined thick-walled components that were fabricated by various deposition parameters. The width of the overlapping area at the overhanging feature decreased as the layer number increased, while the height of the same area increased. The height of the overlapping area in each layer increased with an increase in deposition current and decreased when the deposition speed was increased. These phenomena suggest that the heat input is a major factor that influences the formation of the overhanging feature. Both the deposition current and deposition velocity influence heat input, and thereby have an effect in enhancing the geometrical accuracy of an overhanging feature. The experimental results indicate that the proposed approach facilitates morphology change investigation, providing a sufficient reference for optimizing deposition parameters.

A risk assessment model of spontaneous combustion for sulfide ores using Bayesian network combined with grounded theory

Sulfide ores, collectively referred to as a class of minerals with extensive applications, are increasingly susceptible to spontaneous combustion incidents as the mining environment evolves. The spontaneous combustion of sulfide ores is a complex nonlinear process, and the mechanisms of which remain not fully understood. Consequently, it is challenging to delineate the accident trajectory through traditional accident causation models and subsequently construct a probabilistic model for spontaneous combustion risk. To address this issue, this paper proposed a risk assessment model based on grounded theory and Bayesian network. The advantage of this model is that it employs grounded theory to categorize and organize factors influencing the occurrence of accidents, thereby forming a clear accident trajectory and providing a framework and basis for constructing a probabilistic assessment model. Furthermore, the model presented in this paper introduces the D number theory and the Noisy-OR model to handle uncertainties in the risk assessment process and to establish more rational conditional probability tables. The findings suggest that environmental temperature, heat dissipation conditions, safety awareness, and safety skills are the most influential factors in spontaneous combustion incidents when considering a particular point in time. However, when considering the entire process of sulfide ore pile spontaneous combustion, the temperature of the ore pile is the most critical accident factor to monitor. Therefore, the key to suppressing the spontaneous combustion of sulfide ores lies in reducing environmental temperatures, enhancing heat dissipation, and elevating the safety awareness of relevant personnel.

Design of experimental section of a water tunnel for simulation of heat dissipation condition of seawater-activated battery

Abstract A water tunnel is a crucial experimental apparatus in hydrodynamic research, as the traditional water tunnel has drawbacks such as a small cross-sectional area of the test section and higher costs, which makes it difficult to meet the requirements of a water tunnel for simulating the heat dissipation conditions of the seawater-activated battery. This paper proposes a water tunnel specifically designed for simulating the heat dissipation conditions of seawater-activated batteries, and the water tunnel consists of an external cooling water circulation system and an internal electrolyte circulation system. The experimental section’s design determines the water tunnel’s size and key technical indexes. The temperature distribution contour maps of the experimental section were obtained using Ansys Fluent software simulation. The cooling effect was analyzed, and a cooling water flow rate of 10 m/s was selected. Pressure and velocity contour maps were obtained by simulating the experimental section of the water tunnel. The results show that when the cooling water velocity is 10 m/s, the pressure drop of the experimental section is approximately 1.76 atmospheres. The flow field is uniform and stable, and the heat dissipation power can reach 45.5 kW, meeting the technical requirements.

Investigation on the thermal characteristics of double-driven hydrostatic lead screw micro-feed system

The micro-feed system of the dual-drive hydrostatic lead screw (DDHLS) can overcome the accuracy limitations inherent in traditional hydrostatic lead screw through the process of differential synthesis, thereby achieving exceedingly low speeds and exceptional precision in feed operations. Nevertheless, due to the complex structural form of DDHLS, both heat generation and heat dissipation are different from conventional hydrostatic functional components. Therefore, for DDHLS micro-feed system, it is necessary to deeply investigate its thermal performance and evolution rules to improve its thermal stability. Based on the analysis of multi-field coupling, the accurate thermal model of the DDHLS micro-feed system is formulated. Taking into account the variable viscosity of the oil film and the heat dissipation conditions within the oil film region, the thermal behavior of DDHLS feed system is analyzed systematically. The accuracy of the thermal performance model of DDHLS feed system is verified by experiments. The findings indicate that the DDHLS micro-feed system has better thermal performance than the dual-axis differential feed system based on rolling components. Furthermore, optimizing the heat dissipation pathway of the DDHLS can significantly mitigate the thermal effects exerted by the hydrostatic nut assembly on the screw.

Thermal performance analysis of horseshoe crab shaped fin cold plate

Abstract As we all know, efficient, safe, and stable operation of lithium-ion batteries is the key to ensuring vehicle performance. This type of battery can create a good amount of heat during the driving process of a car. Poor heat dissipation conditions accumulate heat, causing the battery to generate more heat, which leads to a very bad impact. More seriously, it can generate thermal runaway, seriously affecting the safe driving of the car. Therefore, designing an efficient heat dissipation structure is crucial for the safe use of batteries. This article focuses on the thermal performance analysis. In terms of heat dissipation structure design and optimization, a biomimetic horseshoe crab fin cooling plate structure is proposed. Finite element models of the module and cooling plate are established using Solidworks software, and CFD simulation is completed. Six cooling schemes under the flow direction of two cooling media are compared and analyzed with traditional rectangular fin cooling plates. The results showed that the cooling plate with horseshoe crab-shaped fins had better heat transfer performance, and the highest temperature of the battery module was lower.

Enhancing thermal stability of Nd:GGG WGM microdisk lasers via silica integration

Abstract Whispering gallery mode (WGM) resonators, as an integral component of integrated photonics, have attracted considerable attention due to their high Q factor, small footprint, and small mode volume, making them widely applied as microlasers. In this work, Nd:GGG crystal was prepared into a Nd:GGG film with thickness of 1.8 μm through ion implantation-enhanced etching (IIEE) technique, and subsequently, the Nd:GGG film was partened by focused ion beam (FIB) technology to generate a microdisk with diameter of 20 μm. For high-power microcavity lasers, heat generation during laser operation was inevitable. We placed the microdisk on a silica holder and a silica wafer, respectively. The microdisk placed on the silica holder and silica wafer exhibited laser thresholds of 32 μW and 17 μW, respectively. Moreover, due to different heat dissipation conditions, the microdisk placed on the silica holder exhibited a mode shift of 0.13 nm/mW, while the microdisk placed on the silica wafer showed a more stable laser output state with a mode shift of 0.02626 nm/mW.

A two-dimensional semi-analytic thermal model for global temperature distribution predicting and hot spot monitoring in interior permanent magnet synchronous motor

A two-dimensional semi-analytical thermal model (SATM) is presented, aiming to quickly and accurately achieve global temperature distribution predicting and hot spot monitoring for interior permanent magnet synchronous motor (IPMSM). Thereby, it provides a reliable analysis tool for thermal behavior evaluation and prevents undesired consequences induced by excessive temperature rise, which is of great worth and significance in promoting the flourishing of IPMSM. SATM combines the analytical method, lumped parameter thermal network, and finite element analysis to obtain an analytical solution for thermal behavior through mathematical derivation by considering the complicated configuration, heat source distribution, heat dissipation condition, and material thermal dependence. Through SATM, it is possible to observe the global temperature distribution as well as the location and size of hot spots in each element. The temperature distribution gradient on the static is more pronounced than that on the dynamic; secondly, the area with the most severe heating is mainly found on the winding; furthermore, the hot spot on the winding is mainly located a little bit inside the center. Moreover, the thermal behavior of IPMSM at rated load is investigated by numerical analysis and experiments. A comprehensive comparison with SATM is done. The computational deviations between SATM and numerical analysis regarding the hot spot, minimum, and average temperatures on each element are all within 4.06 %. However, SATM consumes only 20.92 % of the time and 68.29 % of the storage of the numerical analysis. The measured data also fully prove the reliability and validity of the comparison. It is certain that SATM can well break through the limitation of the existing non-numerical technique to quickly and accurately achieve global temperature distribution predicting and hot spot monitoring of IPMSM. It provides researchers and engineers engaged in thermal behavior evaluation with good analysis means, design guidance, and optimization direction.

Microstructure evolution and mechanical properties of new Co-free maraging steel produced by wire arc additive manufacturing

In this work, P-MIG is used as additive process, a new low-cost Co-free maraging steel wire is used as raw material to additive manufacturing block component, and the microstructure and mechanical properties of the component is investigated. The microstructure of the component is composed of martensite and austenite, and the closer to the bottom, the more serious the elemental segregation and the more austenite content. From the top to the bottom the high-angle grain boundaries increase and the grain size decrease, the difference of the heat dissipation condition and the thermal cycle are the reasons for this phenomenon. The texture of austenite is mainly Cube texture, and the texture of martensite is Rotated Cube texture and Goss texture. The tensile strength of XD, YD, ZD three directions is 1172 ± 15 MPa, 1021 ± 7 MPa, 1139 ± 16 MPa, respectively, impact toughness is 64.7 ± 1.6 J/cm2, 51.1 ± 5.6 J/cm2, 51.4 ± 3.1 J/cm2, respectively, TRIP effect occurs in the process of tensile, the main mode of fracture in tensile and impact is toughness fracture. The microhardness decreases gradually from bottom to top, which is due to the short-lived aging strengthening by thermal cycle, the change of grain size and GND density. The results of the work reveal the successful application of the new low-cost Co-free maraging steel wire in WAAM and provide an important reference for the adjustment of additive process, subsequent heat treatment and the adjustment of wire composition.

Research on performance of new separated thermoelectric cooler at different pulse currents

This paper studies the performance of a novel split thermoelectric cooler under the different pulsed electrical currents. The investigation focuses on analyzing changes in the cold side temperature of thermoelectric cooler when subjected to different pulse forms. The three-dimensional heat transfer model established through COMSOL was used to investigate the new thermoelectric cooler. The study focused on analyzing the impacts of pulse amplitude, pulse period, pulse waveform, and heat dissipation conditions on the performance of split cooler. The results show that the cooling temperature of split component can be reduced by about 13 K at constant electrical current compared with the conventional component. The temperature of the separated component can be decreased by an additional 2–5 K through the application of pulsed current. The triangle pulse is the best choice for the split component under continuous pulse when the heat dissipation is insufficient. The split thermoelectric component can work more smoothly by using the slant drop triangle pulse compared with the optimized triangle pulse form. The performance of the split thermoelectric component is optimal under a square pulse when there is adequate heat dissipation.

Thermal runaway evolution of a 280 Ah lithium-ion battery with LiFePO4 as the cathode for different heat transfer modes constructed by mechanical abuse

Lithium iron phosphate batteries have been increasingly utilized in recent years because their higher safety performance can improve the increasing trend of recurring thermal runaway accidents. However, the safety performance and mechanism of high-capacity lithium iron phosphate batteries under internal short-circuit challenges remain to be explored. This work analyzes the thermal runaway evolution of high-capacity LiFePO4 batteries under different internal heat transfer modes, which are controlled by different penetration modes. Two penetration cases involving complete penetration and incomplete penetration were detected during the test, and two modes were performed incorporating nails that either remained or were removed after penetration to comprehensively reveal the thermal runaway mechanism. A theoretical model of microcircuits and internal heat conduction is also established. The results indicated three thermal runaway evolution processes for high-capacity batteries, which corresponded to the experimental results of thermal equilibrium, single thermal runaway, and two thermal runaway events. The difference in heat distribution in the three phenomena is determined based on the microstructure and material structure near the pinhole. By controlling the heat dissipation conditions, the time interval between two thermal runaway events can be delayed from 558 to 1417 s, accompanied by a decrease in the concentration of in-situ gas production during the second thermal runaway event.

Application of CNTs – Al2O3/H2O on a Hybrid Nanofluid in Two-Dimensional Unsteady Flow in a Stretching Sheet: Darcy-Forchheimer Model

The fame of carbon nanotube nanoparticles for improving the thermophysical characteristics of fluid molecules has grown recently (Nanoparticles of Carbon nanotubes have attained the fame to enhance the thermophysical properties of fluid molecules). The main objective of this article is to investigate the boundary layer flow of a hybrid nanofluid composed of multi-wall carbon nanotubes (MWCNTs) and single-wall carbon nanotubes (SWCNTs) in combination with alumina and water through a stretching sheet while considering the effects of the magnetic field, thermal radiation, heat dissipation, and slip conditions. Additionally, comparisons and studies of the effects of MWCNTs and SWCNTs nanoparticles on the boundary layer are conducted. The dimensionless similarity transformation is used by the bvp4c algorithm in the MATLAB solver to calculate the numerical solutions of the dimensionless ordinary differential equations. Graphs and tables are used to show the associated model’s physical parameters. In addition, the hybrid nanofluid’s flow pattern is generally slowed down by the magnetic, porosity, and inertia coefficient factors. The rate of heat transfer was boosted by using a larger volume fraction of MWCNTs and SWCNTs.

Neural network and physical enable one sensor to estimate the temperature for all cells in the battery pack

The performance of lithium-ion batteries (LIBs) is sensitive to the operating temperature, and the design and operation of battery thermal management systems reply on accurate information of LIBs' temperature. This study proposes a data-driven model based on neural network (NN) for estimating the temperature profile of a LIB module. Only one temperature measurement is needed for the battery module, which can assure a low cost. The method has been tested for battery modules consisting of prismatic and cylindrical batteries. In general, a good accuracy can be observed that the root mean square error (RMSE) of esitmated temperatures is less than 0.8 °C regardless of the different operating conditions, ambient temperatures, and heat dissipation conditions.

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.

Thermal modeling of high-power satellite power cable and analysis of bundling thermal effect

With the increase of satellite power, the current-carrying and heat dissipation of power cable is increasing significantly and the thermal safety problem becomes prominent. Therefore, the need for accurate modeling and fine design of power cable becomes increasingly urgent. In this paper, the thermal analysis modeling method for high-power cable bundle is proposed based on ground test data, and the heat transfer parameters at the installation and bundling points are obtained. At the same time, the thermal effect of cable bundling is quantitatively analyzed by simulating the splitting and binding power cable bundle. The result indicates that enhancing the radiation heat transfer between cables and the surrounding environment is the most effective means to improve the heat dissipation condition of cable bundles. The thermal model of high-power satellite power cable proposed in this paper can be used as an important basis for the prediction of on-orbit temperature and fine laying design of the power cable.

Design and performance analysis of hot side heat sink of thermoelectric cooler device based on simulation and experiment

AbstractAs for improving the heat diversion capacity of the hot side heat sink of the thermoelectric cooler (TEC), thereby improving the operational performance of the TEC, this study designed a type of double‐embedded flat heat pipe (EFHP) finned heat sink and compared with a standard aluminum (Al) heat sink. In experimental studies, TEC under two heat sinks were placed under different operating currents for heat transfer analysis and performance comparison. The experimental results demonstrated that the EFHP heat sink had better heat diversion ability, effectively improving the operational performance of TEC. When the TEC was input with a current of 6A, the thermal resistance of the double EFHP finned heat sink decreased by 19% compared to the Al heat sink; cooling capacity and coefficient of performance increased by 8.3% and 9.46%, respectively. Further, TEC's cold and hot surface temperatures decreased by 10.83% and 10.2%, respectively, and the heat uniformity of the heat sink improved. In addition, the CFD software Icepak was used to analyze the effects of double flat heat pipe spacing and length on the heat sink and TEC and the performance of two heat sinks and TEC under different heat dissipation conditions and obtained good agreement. This study can provide further guidance and assistance in designing the TEC cooling system.

Influence of Bioactive Glass Addition on TC4 Laser Cladding Coatings: Microstructure and Electrochemical Properties

There is a growing interest in enhancing the bioactivity of TC4-based metallic biomaterials, which are known for their excellent biocompatibility. Bioactive glass (BG) has been recognized for its high potential in promoting bioactivity, particularly in osteo tissue engineering. This study focuses on investigating the influence of BG addition on the microstructure and electrochemical properties of TC4 coatings. The TC4/BG composite coatings were fabricated through laser cladding, and their microstructure was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical properties of the coatings were assessed through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in three different solutions. The results revealed that the incorporation of BG had a significant impact on the microstructure of the TC4 coatings, leading to the formation of a well-defined interface between the TC4 matrix and the BG aggregates. The distribution of BG aggregates within the TC4 matrix coating was found to be random and unrelated to the specific regions of the coating. The metallographic microstructure variations were attributed to different heat dissipation conditions during the laser cladding process. Furthermore, the electrochemical corrosion behavior of TC4/BG composite coatings reveals that they exhibit stability similar to that of passive films and good resistance against media corrosion compared to TC4, while also showing enhanced corrosion resistance in 3.5 wt% NaCl and Dulbecco’s modified Eagle medium (DMEM) solutions, indicating their potential for biomedical applications; however, the corrosion resistance decreases gradually in all solutions, potentially due to the elevated Cl− concentration. Further research can explore bioactivity enhancement of TC4/BG composite coatings and investigate the long-term stability and biological response of these coatings in diverse physiological environments.

An investigation on thermal runaway behaviours of lithium-ion battery with Li(Ni0.6Co0.2Mn0.2)O2 cathode induced by overcharge under different heat dissipation conditions

Lithium-ion batteries (LIBs) are widely used, but there are few studies on their behaviour under different heat dissipation conditions. This paper comparatively investigates the electro-thermal behaviour of LIBs in air, quasi-adiabatic, and adiabatic environments during thermal runaway caused by overcharging. Our study reveals the internal mechanism of overcharging that leads to battery degradation. We find that the battery is more prone to thermal runaway under deteriorating heat dissipation conditions or with an increase in charging rate, but the state of charge (SOC) at the time of thermal runaway is not necessarily correlated with it. Regardless of the conditions, the battery develops a voltage plateau, and the temperature rises during this phase due to the decomposition reaction of the solid electrolyte interface (SEI) film or the electrolyte's reaction with the intercalated lithium. Inconsistent airflow and temperature can affect the battery's temperature and voltage during overcharging. Increased impedance, cathode destruction-including an increase in particle distance, dissolution and deposition of transition metals on the anode, and lithium precipitation on the anode's surface are significant reasons for the battery's degradation due to overcharge. These observations play a crucial role in the storage, transportation and use of LIBs in different environments.

Milling machinability analysis of GW63K rare-earth magnesium alloys based on the concept of clean cutting

GW63K rare-earth magnesium (Mg-RE) alloys have been widely used in various advanced industries for their excellent mechanical properties. However, the machinability of GW63K alloys under clean cutting conditions still needs to be better understood. The novelty of this paper lies in addressing the influences of varying cutting parameters on the milling responses of GW63K Mg-RE alloys as well as the underlying mechanisms. A full-factorial design of experiments was conducted under dry cutting and minimum quantity lubrication (MQL) conditions. A three-tooth milling cutter with a diameter of 12 mm was used during the investigation. The critical milling outputs involving cutting forces, machining temperatures, and surface quality attributes were carefully analyzed. The results indicate that the cutting force highly depends on the feed per tooth, and the cutting temperature is raised with the increased cutting speed and feed per tooth. The MQL is found capable of reducing the milling temperature by 10.8 °C on average compared with dry cutting. The MQL shows benefits in improving the cutting performances of tools and surface quality of Mg-RE alloys by reducing the tool-workpiece friction coefficient and enhancing the heat dissipation conditions of the chip contact surface. In addition, lower feed per tooth and higher cutting speeds under MQL conditions are suggested for the milling of Mg-RE alloys while ensuring processing efficiency.

Experimental research and optimization of a thermoelectric generator excited by pulsed combustion mode under limited heat dissipation for combined heat and power supply

In this paper, a scheme of pulse combustion mode with pulse input of gas is proposed to solve the problems of low output electrical performance and energy conversion efficiency of combustion-based thermoelectric systems under limited heat dissipation conditions, which is based on experiments. The characteristics of the thermoelectric system show that pulse combustion mode can increase the instantaneous temperature difference, so as to achieve the excitation effect on the output power. The relationships among output power, system efficiency, excitation intensity and pulse input parameters, and the geometry of thermoelectric modules are obtained. The influence of pulse input parameters on the excitation intensity is interactive, and top dead center of pulse inlet power is the parameter that has the greatest influence on the performance. Compared to the constant combustion mode, the pulse combustion mode can increase the output power by up to 28.3%. A maximum output power of 7.15 W with air-cooled heat dissipation and a maximum system efficiency of 3.26% were experimentally obtained, which is a 30% increase in efficiency over current air-cooled heat dissipation thermoelectric systems. Therefore, this paper can provide solutions for more practical power supply, provide effective and feasible guidance for the study of thermoelectric systems, and provide useful insights into the electrical properties of thermoelectric systems.

Thermal Runaway Behaviors and Kinetics of NCM Lithium-Ion Batteries at Different Heat Dissipation Conditions

The lithium-ion battery (LIB) thermal runaway is triggered by the exothermic reactions between electrode materials and other active substances such as electrolytes. In this study, the effects of ambient temperature and heat transfer coefficient on the thermal responses and chemical kinetic features of LiNi1/3Co1/3/Mn1/3O2/graphite battery thermal runaway at high-temperature abuse conditions are investigated using a validated 2D axisymmetric model. With varied heat transfer coefficients of the LIB, the corresponding runaway, critical, and safety operation zones at different ambient temperatures are quantitatively distinguished. The results reveal that, with increased heat transfer coefficient, the critical ambient temperature, T c, triggering thermal runaway increases. However, T c almost remains 430 K when the heat transfer coefficient is higher than 25 W/(m2K). Additionally, based on the thermal response of LIB, the ambient heat absorption stage, ambient heat dissipation stage, and dramatic heat release stage in thermal runaway are defined. It is found that a higher heat transfer coefficient efficiently causes a shorter ambient heat absorption stage, which is the primary reason for the reduced delay time for the thermal runaway. Further, kinetic analysis is conducted at different heat exchange conditions, and the correlation between LIB thermal responses and the heat release of side reactions in different operation zones is clarified. Specifically, the reactions between the electrolyte and negative/positive electrodes are the most exothermic and most influential of all side reactions, and their influence on the maximum temperatures and runaway delay times is promoted with an elevated heat transfer coefficient.