bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Hollow Microspheres LiNi0.5Mn1.5O4 Coated With Al2O3 and Characterization of the Electrochemical Capabilities
Authors: Li Shiyou , Liang Wenbiao , Xie Jing , Wei Yuan , Cui Xiaoling 
Published: December 2019

AbstractSpinel LiNi0.5Mn1.5O4 (LNMO) has become one of the most practical power lithium-ion battery cathode materials due to its advantages of three-dimensional Li+ diffusion channel, higher potential window (3.5–5V), high-energy density (∼660 Wh/kg), and high-power density. In this manuscript, a hollow spherical LNMO material with large size and high crystallinity is prepared by a modified coprecipitation method using ethyl alcohol as a peptizator. Subsequently, the prepared LNMO material is further modified by an Al2O3 coating to improve its cycle stability. Results show that the initial discharge-specific capacity of LNMO material with 1 wt% Al2O3 coating is 133.7 mAh g−1 at 0.2 C rate, and the capacity retention rate is 97.7% after 100 cycles. The effective increase in the cycle life of the battery can be attributed to the uniform and dense Al2O3 coating on the surface of the material.
Cathode Chemistries and Electrode Parameters Affecting the Fast Charging Performance of Li-Ion Batteries
Authors: Zhao Rui , Liu Jie , Ma Fai 
Published: December 2019

Abstract
Li-ion battery fast-charging technology plays an important role in popularizing electric vehicles (EV), which critically need a charging process that is as simple and quick as pumping fuel for conventional internal combustion engine vehicles. To ensure stable and safe fast charging of Li-ion battery, understanding the electrochemical and thermal behaviors of battery electrodes under high rate charges is crucial, since it provides insight into the limiting factors that restrict the battery from acquiring energy at high rates. In this work, charging simulations are performed on Li-ion batteries that use the LiCoO2 (LCO), LiMn2O4 (LMO), and LiFePO4 (LFP) as the cathodes. An electrochemical-thermal coupling model is first developed and experimentally validated on a 2.6Ah LCO based Li-ion battery and is then adjusted to study the LMO and LFP based batteries. LCO, LMO, and LFP based Li-ion batteries exhibited different thermal responses during charges due to their different entropy profiles, and results show that the entropy change of the LCO battery plays a positive role in alleviating its temperature rise during charges. Among the batteries, the LFP battery is difficult to be charged at high rates due to the charge transfer limitation caused by the low electrical conductivity of the LFP cathode, which, however, can be improved through doping or adding conductive additives. A parametric study is also performed by considering different electrode thicknesses and secondary particle sizes. It reveals that the concentration polarization at the electrode and particle levels can be weaken by using thin electrodes and small solid particles, respectively. These changes are helpful to mitigate the diffusion limitation and improve the performance of Li-ion batteries during high rate charges, but careful consideration should be taken when applying these changes since they can reduce the energy density of the batteries.
Theoretical Analysis for Combined Compact Evaporative Cooler Utilizing Nanostructured Surfaces
Authors: Ismael Laith , Ma Hongbin 
Published: December 2019

Abstract
A detailed mathematical model is modified that describes heat and mass transfer through Combined Compact Evaporative Cooler CCEC using mono-scale sintered particles coating. The model accounts for the effects of particles size, Reynold’s number, and channel spacing on system performance for certain operating conditions. In this study, a Kelvin-Clapeyron equation is utilized to obtain numerical data for an evaporating meniscus in the wet channels and compared to the plain surface. The results indicate that porous coatings enhanced evaporative heat and mass transfer in the wet channels significantly, compared to the plain wet channels walls, due to wicking water that covers entire heated surfaces.
Experimental Investigation of a Miniature Ejector Using Water As Working Fluid
Authors: Dong Jingming , Xia Yuxin , Ma Hongbin , Song He , Zhao Zhongxi , Liang Tao 
Published: December 2019

Abstract
This paper presents an experimental investigation of a miniature ejector using water as the working fluid. The investigated ejector cooling system can be used to keep the temperature of an electric chip below ambient temperature. The authors tested the effects of working conditions, the nozzle exit position (NXP), and the area ratio on the ejector’s performance. Experimental results show that the miniature ejector works well in the high-temperature evaporator (HTE) under temperatures ranging from 55 °C to 70 °C and can achieve a 0.66 coefficient of performance (COP). With the increase of the NXP, the COP decreased, while the critical condensing pressure first increased and then decreased. As the area ratio of the miniature ejector increased, the COP increased, and the critical condensing pressure decreased.
A Novel Thermal Solution for Electronics: Alumina Flat-Plate Oscillating Heat Pipe
Authors: Tian Bohan , Ma Hongbin , Deming Yang , Xu Jiujun , Wang Zhiyong , Zhao Nannan 
Published: December 2019

Abstract
The heat flux in electronics requires the thermal management of printed circuit boards (PCBs) using two-phase cooling methods. In this study, an integrated ceramic heat transfer device, the alumina flat-plate oscillating heat pipe, is developed. The device was fabricated by pressing and sintering procedures, and the inner serpentine channels were simultaneously formed during sintering without brazing or separated caps. This novel manufacturing process simplifies the fabrication of the macrochannels inside ceramic devices and provides a new method for fabricating ceramic two-phase cooling devices. This paper presents an analysis of the internal channel’s formation mechanism and illustrates the major factors of densification. Micro-computed tomography (Micro-CT) scanning was adopted to assess the macrostructure, and SEM was used to characterize the microstructure of the alumina OHP. Water was charged inside the device as the working fluid. The effects of the power input, orientation, operating temperature and filling ratio on the heat transfer performance were investigated. The experimental results show that the alumina OHP has a high heat transport capability. When the OHP structure is embedded inside the alumina and charged with water, the thermal resistance can be reduced by 97%.
Three-Dimensional Simulation of Bubble Behavior and Mass Transfer for CO2 Absorption in Nanoabsorbents
Authors: Li Lirong , Kang Yong Tae 
Published: December 2019

Abstract
CO2 absorption performance in gas-liquid system is affected by nanoparticles. The enhancement mechanisms involved have been extensively paid attention. The CO2 gas bubble behaviors and the characteristics of the nanoparticle motion have been clarified in the present study. The equivalent substitution method is used to regard the liquid with nanoparticles as a continuous term with changed physical properties, that is, nanofluid. Therefore, the volume-of-fluid (VOF) method is employed to well predict the gas bubble behaviors and mass transfer coefficient in nanofluid. It is found that the mass transfer coefficient in the gas-liquid system for CO2 absorption can be significantly enhanced by Al2O3 nanoparticles. With the increase of nanoparticles volume concentration, the surface renewal frequency increases dramatically. The discrete-particle-method (DPM) is adopted to track the motion of nanoparticles. In this way, the deformation of the bubbles and the motion of the nanoparticle are well captured. It is concluded that the enhanced mass transfer coefficient in gas-liquid-nanoparticle system is not only related to the Brownian motion of the particles, but also related to the nanoparticle deduced turbulence in the liquid field.
Theoretical Analysis of Evaporation Heat Transfer in the Thin-Film Region of Nanofluids
Authors: Zhao Nannan , Lin Huan , Su Fengmin , Fu Benwei , Ma Hongbin , Tian Bohan 
Published: December 2019

Abstract
A significantly higher heat transfer coefficient can be achieved through thin-film evaporation. Nanofluids also have significant enhancements in heat transfer. In the current investigation, based on the principle of conservation of momentum and the Young-Laplace equation, considering the effects of bulk flow and nanofluids concentration variation, a mathematical model of evaporative heat transfer of nanofluids is established. The different performances of different concentrations of nanofluids in the thin film evaporation heat transfer process are discussed. The results show that with the change of nanofluids concentration, the surface tension, dynamic viscosity, thermal conductivity and density will be changed, and surface tension plays an important role in the thin film evaporation heat transfer process. That will lead to a significant effect on the thin-film profile, interface temperature, heat flux in the thin-film region of the nanofluids.
Near-Field Radiative Heat Transfer Between Mie Resonance-Based Metamaterials Made of Coated Nonmagnetic Particles
Authors: Lu Lu , Song Jinlin , Zhou Kun , Cheng Qiang 
Published: December 2019

Abstract
Near-field radiative heat transfer between Mie resonance-based metamaterials composed of SiC/d-Si (silicon carbide and doped silicon) core/shell particles immersed in aligned nematic liquid crystals are numerically investigated. The metamaterials composed of core/shell particles exhibit superior performances of enhanced heat transfer and obvious modulation effect when compared to that without shell. The underlying mechanism can be explained that the excitation of Fröhlich mode and epsilon-near-zero (ENZ) resonances both contribute to the total heat flux. Modulation of near-field radiative heat transfer can be realized with the host material of aligned nematic liquid crystals. The largest modulation ratio could be achieved as high as 0.45 for metamaterials composed of core/shell SiC/d-Si particles, and the corresponding heat flux is higher than other similar materials such as LiTaO3/GaSb and Ge/LiTaO3. While with the same volume filling fraction, the modulation ratio of that composed of SiC particles is only 0.2. We show that the core/shell nanoparticles dispersed liquid crystals (NDLCs) have a great potential in enhancing the near-field radiative heat transfer in both the p and s polarizations with the radii of 0.65 μm, and Mie-metamaterials are shown for the first time to modulate heat flux within sub-milliseconds.
Numerical Investigation of Flow Boiling in a Manifold Microchannel Heat Sink With Conjugate Heat Transfer
Authors: Sun Zhichuan , Luo Yang , Li Junye , Li Wei , Zhang Jingzhi , Zhang Zhengjiang , Wu Jie 
Published: December 2019

Abstract
The manifold microchannel heat sink receives an increasing number of attention lately due to its high heat flux dissipation. Numerical investigation of boiling phenomena in manifold microchannel (MMC) heat sinks remains a challenge due to the complexity of fluid route and the limitation of numerical accuracy. In this study, a computational fluid dynamics (CFD) approach including subcooled two-phase flow boiling process and conjugate heat transfer effect is performed using a MMC unit cell model. Different from steady-state single phase prediction in MMC heat sink, this type of modeling allows for the transient simulation for two-phase interface evolution during the boiling process. A validation case is conducted to validate the heat transfer phenomenon among three phases. Besides, this model is used for the assessment of the manifold dimensions in terms of inlet and outlet widths at the mass flux of 1300 kg/m2·s. With different ratios of inlet-to-outlet area, the thermal resistances remain nearly stable.
Molecular Dynamics Study on Effect of Interface Between Silicon and Silicon Carbide Crystals on Phonon Heat Conduction on Nanoscale
Authors: Nie Xianhua , Zhao Li , Deng Shuai , Zhang Yue , Du Zhenyu 
Published: December 2019

Abstract
Both silicon (Si) and silicon carbide (SiC) are promising materials used in nano-electro-mechanical system (NEMS), however, the understanding on its phonon heat conduction is rare, which restrict the performance improvement of NEMS. Moreover, the effects of the interface between crystals, which could significantly impact the phonon transport, on heat conduction are not sufficient in the existing publication pool. In this paper, two systems, Si/Si and Si/SiC, are simulated at different temperatures and temperature differences using molecular dynamics simulation and the results were analyzed.
The temperature of Si inside Si/SiC system was set at 280K, and the temperatures of SiC were set as a certain absolute value based on temperature difference setting. Meanwhile, 6 groups of temperature difference are applied as simulated conditions. In addition, simulated results from Si/Si system are also applied in comparative analysis as a reference group. The results suggested that the existence of the interface of Si/SiC system would reduce the capability of heat conduction compared to the heat conduction of Si/Si and reverse temperature differences are discovered. When the average temperature is higher than 280K, the heat conduction rate of Si/SiC system is higher than that of Si/Si system initially and as the temperature differences between crystals increases to 60.90K, the heat conduction rate of Si/Si system is higher than that of Si/SiC system. Similar conclusion can also be obtained when the average temperature is lower than 280K. This work provides an open opportunity to study the effect of interface on phonon heat conduction between crystals at typical temperature differences and average temperatures.
An Electromechanical Model for Electrowetting
Authors: Huang Deng , Qian Fang , Zhang Wenyao , Zhao Cunlu , Li Wenbo , Wang Qiuwang 
Published: December 2019

Abstract
We present an electromechanical model for analysis of electrowetting by considering the balance between an electric force and a surface tension force acting on the contact line of three phases, namely the droplet (D) phase the substrate (S) phase and the ambiance (A) phase. We show that the electric force acting on the three-phase contact line generally is contributed by the Maxwell stresses at the ambiance-substrate (A-S) interface, the droplet-substrate (D-S) interface, and the droplet-ambiance (D-A) interface. It was identified that the change of contact angle in electrowetting is essentially a consequence of the modification of the electric force on the contact line. For a classical electrowetting configuration, we show that the electric force on the contact line is mainly due to the Maxwell stresses at the D-A interface. Then we examine comprehensively how the electric force on the contact line varies with the permittivity difference between A and S phases, the contact angle and size. It was found that our model agrees excellently with the classical Yong-Lippmann (Y-L) model when the permittivities of A and S phases are equal, while the difference between the two increases as the permittivity difference between A and S phases increases. The electric force increases with the increase of the contact angle for a given droplet size. Our model approaches the Y-L model with the increasing droplet size. The findings are complementary to the classical Y-L model and provide new insights into the electrowetting.
Thermal Property Enhancement of Liquid Metal Used As Thermal Interface Material by Mixing Magnetic Particles
Authors: Ma Xianfeng , Li Gen , Zheng Xuelin , Wang Xiaozhong , Wang Zhongcheng , Ji Yulong 
Published: December 2019

Abstract
The usage of low melting temperature alloys (LMAs) as thermal interface materials (TIMs) has attracted more and more attention for their high thermal conductivity. However, the wettability between liquid metal and ordinary metal surface was poor, which results in high thermal interface resistance. The thermal and physical properties of LMAs can be modified by adding nano or micro particles. In this study, the room temperature liquid metal (gallium, indium and tin eutectic) was used as TIM and its properties were modified by mixing magnetic nickel particles. Further, the effects of magnetic field application on the thermal performance of modified LMAs were evaluated by steady state method with specially designed sample holder. Results showed that the thermal conductivity of liquid metal mixed with nickel particle increased from 27.33 W/(m · K) to 33.33 W/(m · K) with the application of magnetic field.
Numerical and Experimental Investigation of Boiling Heat Transfer for Subcooled Water Flowing in a Small-Diameter Tube
Authors: Shibahara Makoto , Liu Qiusheng , Hata Koichi , Fukuda Katsuya 
Published: December 2019

Abstract
Numerical simulation of boiling heat transfer for subcooled water flowing in a small-diameter tube was conducted using the commercial computational fluid dynamics (CFD) code, PHOENICS ver. 2013. A small-diameter tube (d = 1.0–2.0 mm) was modeled in the simulation. A uniform heat flux with an exponential function was given at the inner tube wall as the boundary conditions. The inner wall boundary condition was set to a non-slip. The inlet temperature ranged from 302 to 312 K. The flow velocities of d = 1.0 mm and d = 2.0 mm are 9.29 m/s and 2.34 m/s, respectively. The transient analysis was carried out from the non-boiling region since the heat flux increased with time in the author’s experiments. The governing equations including the energy equation were discretized using the finite volume method in the PHOENICS code. The SIMPLE method was applied for the numerical simulation. For modeling boiling phenomena in the tube, the Eulerian-Eulerian two-fluid model was adopted using the interphase slip algorithm of PHOENICS code. In the experiment, a platinum tube was used as the experimental tube (d = 1.0–2.0 mm) to conduct joule heating by direct current. The distilled and deionized water was pressured by the pressurizer. The heat generation rate of the tube was controlled with the exponential function to obtain the transient heat transfer characteristics from the non-boiling region. The surface superheat increased as the heat flux increased in the experiment. The numerical simulation predicted the experimental data well. When the heat flux of the experiment was reached to the CHF point, the predicted value of heat transfer coefficient was approximately 3.5 % lower than that of the experiment.
Non-Newtonian Droplet Generation in a Flow-Focusing Microchannel
Authors: Xue C. D. , Sun Z. P. , Li Y. J. , Qin K. R. 
Published: December 2019

Abstract
The emergence of microfluidic droplets offers new opportunities to advance biomedical engineering, food production, and energy storage applications. These applications always involve complex fluids exhibiting obvious non-Newtonian behavior. Droplet generation has been extensively addressed, while the complete understanding of droplet generation in non-Newtonian fluid system is still nascent. Here, we present the study of non-Newtonian droplet generation in a flow-focusing microchannel. Polyethylene oxide aqueous solutions are used as the dispersed phase, while olive oil serves as the continuous phase to induce the generation. The molecular weight of polymer is constant while the concentrations are varied from dilute to semi-dilute regimes that are rarely explored in existing studies. The main features of non-Newtonian droplet generation are first identified, after which the concentration-dependent dripping to jetting transitions are clarified. The effects of shear thinning and elasticity on droplet generation are then separately investigated. We finally propose a scaling relation to predict the primary droplet size with the satellite droplets neglected. These results can not only extend the fundamental theory of droplet microfluidics but also facilitate the practical applications.
Numerical Study on the Mechanism of Heat Transfer Enhancement in Fe3O4 Nanoferrofluids With Magnetic Field
Authors: Wang Chenfei , Gao Dongdong , Bai Minli , Wang Peng , Li Yubai 
Published: December 2019

Abstract
Nanofluids is reported to significantly enhance heat transfer but with little cost of pressure loss. To further the enhancement of heat transfer using Fe3O4 nanofluids, a magnetic field is employed to control the trajectory of Fe3O4 nanoparticles. A numerical study is conducted with commercial soft ANSYS FLUENT and the simulations are done with a two-phase flow approach named Euler-Lagrange. By comparing heat transfer of laminar flow in a horizontal tube with magnetic field or not, various volume fraction (0.5%/2%) and Reynolds numbers (Re = 200–1000) are considered. Results show that magnetic field contributes an average 4% promotion in convective heat transfer coefficients compared with the condition of no magnet. The mechanism of the enhancement of heat transfer with magnetic field is explored based on the analysis of velocity field. Fe3O4 Nanoparticles move up and down under the magnetic force, and convective heat transfer is enhanced because of the disturbance of the Fe3O4 nanoparticles. Slip flow between the base fluid and nanoparticles also contributes to the enhancement of heat transfer.
Laser Ablation of Crystalline Material With and Without Water on Material Surface
Authors: Yao Wenlong , Yan Li , Qi Yunshu , Mei Ning 
Published: December 2019

Abstract
The phase and morphological changes of crystalline material during laser internal ablation with and without water on the material surface are studied using molecular dynamics simulations. The atomic image of the material morphology was obtained by recording the velocity and position variation of atoms. Temperature distribution contour of the crystalline material along the ablation process are charted by statistical physics method. Furthermore, density variation and phase variation contour of water are also charted. The results suggest that: First, during the ablation process of crystalline materials, energy transfer occurs between water and crystalline materials. Supercritical water is formed first, which restrains the sputtering of crystalline materials due to phase explosion and puts off the sputtering. Then the physical state of water changes from liquid to gaseous. Second, with water on the surface, the cavity shape is different from that without water, the width of upper part of cavity is decreased. Third, the volume of the cavity is affected by the thickness of the water layer.
Energy Harvesting Performance of Vertically Staggered Rectangle-Through-Holes Cantilevered in Piezoelectric Vibration Energy Harvester
Authors: Gao Shan , Ao Hongrui , Jiang Hongyuan 
Published: December 2019

Abstract
Piezoelectric vibration energy harvesting technology has attracted significant attention for its applications in integrated circuits, microelectronic devices and wireless sensors due to high power density, easy integration, simple configuration and other outstanding features. Among piezoelectric vibration energy harvesting structures, cantilevered beam is one of the simplest and most commonly used structures. In this work, a vertically staggered rectangle-through-holes (VS-RTH) cantilevered model of mesoscale piezoelectric energy harvester is proposed, which focuses on the multi-directional vibration collection and low resonant frequency. To verify the output performances of the device, this paper employs basic materials and fabrication methods with mathematical modeling. The simulations are conducted through finite element methods to discuss the properties of VS-RTH energy harvester on resonant frequency and output characteristics. Besides, an energy storage circuit with high power collection rate is adopted as collection system. This harvester is beneficial to the further application of devices working with continuous vibrations and low power requirements.