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Effects of primary flow temperature on phase change characteristics in hydrogen recirculation ejector for PEM fuel cell system

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2024年 68卷 1133-1143页

作者： Han, Jiquan Chen, Yuhang Feng, Jianmei Wang, Lingzi Peng, Xueyuan Xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xian Jiaotong Univ XJTU Sch Energy & Power Engn 28 West Xianning Rd Xian 710049 Peoples R China

The hydrogen recirculation ejector, known for its low cost and simple structure, has garnered widespread attention in PEM fuel cell applications. As a fluid-driven passive component, the fluid dynamics inside the ejector play a pivotal role in determining its entrainment performance. This study explores the impact of the primary flow temperature on phase change characteristics based on the Euler-Lagrange model. Results indicate that at a primary flow temperature of -40 degrees C, the mass flow rate of droplets at the outlet reaches 285.2 mg/s, representing a condensation efficiency of 24.1%. Concurrently, condensation elevates the outlet temperature by 31.2 degrees C, resulting in an 8.8% reduction in the entrainment ratio. The mass flow rate of droplets decreases significantly as the primary flow temperature increases. As the temperature rises to 60 degrees C, homogeneous droplets vanish entirely. Simultaneously, foreign heterogeneous droplets evaporate by 42.0%, attributed to the negative subcooling degree at the diffuser and outlet pipe. This study emphasizes the significance of controlling the primary flow temperature for the hydrogen recirculation ejector.

关键词： Ejector Hydrogen recirculation PEM fuel cell Phase change Two-phase flow

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Tailoring surface wetting states for ultrafast solar-driven water evaporation

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ENERGY & ENVIRONMENTAL SCIENCE 2020年第7期13卷 2087-2095页

作者： Guo, Youhong Zhao, Xiao Zhao, Fei Jiao, Zihao Zhou, Xingyi Yu, Guihua Univ Texas Austin Mat Sci & Engn Program Austin TX 78712 USA Univ Texas Austin Dept Mech Engn Austin TX 78712 USA Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Solar-driven interfacial evaporation has significant potential to improve the energy utilization efficiency and provides a means for sustainable seawater desalination and water purification technologies. Although rational design of evaporative materials and surfaces is essential to the interfacial solar water vaporization process, tailoring the surface wettability states of solar evaporators to accelerate the vapor generation rate remains unexplored. Here we demonstrate hydrophilic hydrogel evaporators with hydrophobic island-shaped patches, capable of achieving a record evaporation rate of similar to 4.0 kg m(-2) h(-1) with 93% efficiency under 1 sun irradiation (1 kW m(-2)). This exceptional high rate results from both wetting regions, which function synergistically. The increased thickness of the water layer in the hydrophilic region leads to the rapid escape of water molecules, while relatively long contact lines promise considerable water evaporation from the hydrophobic region, further contributing to this process. Molecular dynamics simulations provide a consistent outcome on a molecular basis, in which an inhomogeneous surface wetting property could modulate the escape behavior of water molecules to speed the evaporation. Under natural sunlight, a 3D printed portable solar water purification jug using this hydrogel evaporator delivers purified water far above the EPA drinking water standards, highlighting its potential for water purification.

关键词： Evaporation

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Diagnosis method to identify diaphragm state of diaphragm compressors for hydrogen refueling stations based on dynamic oil pressure

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2024年第PartD期49卷 1043-1055页

作者： Ren, Shengdong Jia, Xiaohan Zhang, Jiatong Li, Xueying Zhang, Shengtao Peng, Xueyuan Xi An Jiao Tong Univ Sch Energy & Power Engn Xian Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Peoples R China Shandong Himile Mfg Co Ltd 1 Haomai Rd Weifang 261500 Peoples R China

Frequent diaphragm rupture of diaphragm compressors is a severe issue in hydrogen refueling stations, generally occurring when the diaphragm collides violently with the oil plate. The oil pressure exhibits distinct properties in different working conditions, due to the oilgas cooperative working characteristics of diaphragm compressors. This paper proposes a diagnosis method to identify the state of the diaphragm, separating the maximum and minimum oil pressures from the complex working parameters as characteristic signals. Especially, this method can forewarn the collision. The precise reason for the failure can also be identified combined with the overflowed oil flow. Several common fault types were reproduced and evaluated to verify this method's reliability. Experimental results confirmed that this method could accurately identify the diaphragm states, and can issue a collision warning 25 min in advance for a 45 MPa diaphragm compressor even in accelerated tests. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Hydrogen refueling station Diaphragm compressor Diagnosis method Dynamic oil pressure

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Experimental study on thermal performance of a loop heat pipe with a bypass line

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2020年 147卷 1页

作者： Liu, Lei Yang, Xiaoping Yuan, Bo Ji, Xinyu Wei, Jinjia Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Shaanxi Peoples R China Tan Jiaotong Univ Shaanxi Key Lab Energy Chem Proc Intensificat Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The loop heat pipe with both flat evaporator and boiling pool (NLHP) has much higher maximum heat flux than conventional loop heat pipe (LHP). However, the serious temperature overshoot and the startup time difference between the evaporator and boiling pool have become a bottleneck of the NLHP. In this study, a loop heat pipe with a bypass line (BLHP) is proposed to improve the startup characteristics of the NLHP. The effects of the bypass line, time difference, boiling pool heat load and evaporator heat load on the thermal performance of the BLHP are experimentally investigated. The results indicate that the bypass line, which is installed between the condenser outlet and the first vapor line, accelerates the return of working fluid and reduces the adverse effect of the heat leakage. The temperature overshoot is virtually eliminated and the BLHP can operate stably at various evaporator and boiling pool heat loads under a broad range of time differences. Furthermore, the BLHP reduces the heating wall temperature by 3.9-8.1 degrees C and thermal resistance by more than 10% under various heat loads compared with the NLHP. While maintaining the heating wall temperature within 85 degrees C, the maximum heat flux is 39.3 ***(-2), which is much higher than most conventional LHPs using methanol as working fluid. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Electronics cooling Loop heat pipe Temperature overshoot Startup characteristics Bypass line

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Prediction of dryout-type CHF for rod bundle in natural circulation loop under motion condition

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NUCLEAR engineering AND TECHNOLOGY 2020年第4期52卷 721-733页

作者： Huang, Siyang Tian, Wenxi Wang, Xiaoyang Chen, Ronghua Yue, Nina Xi, Mengmeng Su, G. H. Qiu, Suizheng Xi An Jiao Tong Univ Sch Nucl Sci & Technol Shaanxi Key Lab Adv Nucl Energy & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Nucl Power Inst China CNNC Key Lab Nucl Reactor Thermal Hydraul Technol Chengdu 610213 Peoples R China Wuhan Second Ship Design & Res Inst Wuhan 430205 Peoples R China

In nuclear engineering, the occurrence of critical heat flux (CHF) is complicated for rod bundle, and it is much more difficult to predict the CHF when it is in natural circulation under motion condition. In this paper, the dryout-type CHF is investigated for the rod bundle in a natural circulation loop under rolling motion condition based on the coupled analysis of subchannel method, a one-dimensional system analysis method and a CHF mechanism model, namely the three-fluid model for annular flow. In order to consider the rolling effect of the natural circulation loop, the subchannel model is connected to the one-dimensional system code at the inlet and outlet of the rod bundle. The subchannel analysis provides the local thermal hydraulic parameters as input for the CHF mechanism model to calculate the occurrence of CHF. The rolling motion is modeled by additional motion forces in the momentum equation. First, the calculation methods of the natural circulation and CHF are validated by a published natural circulation experiment data and a CHF empirical correlation, respectively. Then, the CHF of the rod bundle in a natural circulation loop under both the stationary and rolling motion condition is predicted and analyzed. According to the calculation results, CHF under stationary condition is smaller than that under rolling motion condition. Besides, the CHF decreases with the increase of the rolling period and angular acceleration amplitude within the range of inlet subcooling and mass flux adopted in the current research. This paper can provide useful information for the prediction of CHF in natural circulation under motion condition, which is important for the nuclear reactor design improvement and safety analysis. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC.

关键词： Dryout CHF Natural circulation Motion condition

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UNCERTAINTY AND SENSITIVITY ANALYSIS OF PHEBUS FPT-1 EXPERIMENT BASED ON SEVERE ACCIDENT ANALYSIS CODE ISAA 31

UNCERTAINTY AND SENSITIVITY ANALYSIS OF PHEBUS FPT-1 EXPERIM...

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31st International Conference on Nuclear engineering (ICONE) - 24/7 Clean Nuclear Energy - Solution for Global Warming

作者： Yang, Hao Zhang, Bin Li, Jishen Gao, Pengcheng Zhang, Zhiran Miao, Fan Xi An Jiao Tong Univ Sch Nucl Sci & Technol Xian Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China

ISBN: (纸本)9780791888315

Since the Three Mile Island nuclear accident, international research on severe accidents has advanced through a combination of experimental studies and numerical simulations. The intricate physical processes and chemical phenomena involved in severe reactor accidents have led to a heavy reliance on empirical parameters in existing severe accident analysis programs, generating significant uncertainties. As a result, there is growing interest in applying systematic analysis programs combined with uncertainty quantification methods to evaluate potential severe accident consequences, a topic receiving considerable attention among researchers in severe accident analysis. In 2019, Europe initiated the MUSA project, an international collaboration focusing on severe accident management and uncertainty. The project centers on a series of severe accident uncertainty analysis studies based on the Phebus FPT1 experiment. This serves as a valuable tool for assessing severe accident analysis code effectiveness in simulating severe reactor accident progression and offers an opportunity to analyze and enhance code physical models. Previous numerical analysis studies using the integrated severe accident analysis program ISAA for the FPT experiment revealed the necessity for significant estimations, particularly in core degradation and source term release. This underscores the importance of conducting uncertainty and sensitivity studies on parameters affecting numerical simulation results using advanced uncertainty analysis methods. In this study, we employed a self-developed uncertainty analysis tool to conduct random sampling analysis based on Latin hypercube sampling for various uncertainty parameters, including experimental modeling data and code model parameters. Utilizing the Wilks theory, the study conducted uncertainty quantification studies on the thermalhydraulic results and hydrogen production in the FPT1 experiment. Data comparison shows the current oxidation model of ISA

关键词： Severe Accident ISAA Phebus FPT1 Wilks' formula Uncertainty analysis Sensitivity analysis

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A numerical investigation on dynamics of ferrofluid droplet in nonuniform magnetic field

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NUMERICAL HEAT TRANSFER PART A-APPLICATIONS 2019年第10期75卷 690-707页

作者： Ling, Kong Guo, Kai-Kai Zhang, Shuai Tao, Wen-Quan Xi An Jiao Tong Univ Key Lab Thermofluid Sci & Engn MOE 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China Xian ShuFeng Technol Informat Ltd Xian Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

This article presents a 3D numerical investigation on ferrofluid droplet motion in magnetic field using VOSET. A nonuniform magnetic field mimicking the one produced by an electric wire loop was generated in a finite computational domain. A validation problem on droplet deformation in uniform magnetic field was first studied, and it gives consistent aspect ratios with reported experiments. The simulation revealed an entire process of the ferrofluid droplet movement, and the influences by the intensity of the magnetic field was investigated and analyzed. Finally, a set of simulations were conducted for net magnetic force on spherical droplet, and the achieved data led to a correlation, which gives accurate prediction in the magnitude of the magnetic force and can be applied to droplet with a certain degree of deformation.

关键词： Deformation

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Implicit-explicit finite-difference lattice boltzmann method for compressible flows

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INTERNATIONAL JOURNAL OF MODERN PHYSICS C 2007年第12期18卷 1961-1983页

作者： Wang, Y. He, Y. L. Zhao, T. S. Tang, G. H. Tao, W. Q. Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Xian 710049 Shaanxi Peoples R China Hong Kong Univ Sci & Technol Dept Mech Engn Hong Kong Hong Kong Peoples R China

We propose an implicit-explicit finite-difference lattice Boltzmann method for compressible flows in this work. The implicit-explicit Runge Kutta scheme, which solves the relaxation term of the discrete velocity Boltzmann equation implicitly and other terms explicitly, is adopted for the time discretization. Owing to the characteristic of the collision invariants in the lattice Boltzmann method, the implicitness can be completely eliminated, and thus no iteration is needed in practice. In this fashion, problems (no matter stiff or not) can be integrated quickly with large Courant Friedriche-Lewy numbers. As a result, with our implicit-explicit finite-difference scheme the computational convergence rate can be significantly improved compared with previous finite-difference and standard lattice Boltzmann methods. Numerical simulations of the Riemann problem, Taylor vortex flow, Couette flow, and oscillatory compressible flows with shock waves show that our implicit-explicit finite-difference lattice Boltzmann method is accurate and efficient. In addition, it is demonstrated that with the proposed scheme non-uniform meshes can also be implemented with ease.

关键词： lattice Boltzmann method implicit-explicit finite-difference compressible flows.

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A study on the dynamic characteristics of the secondary loop in nuclear power plant

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NUCLEAR engineering AND TECHNOLOGY 2021年第5期53卷 1436-1445页

作者： Zhang, J. Yin, S. S. Chen, L. Ma, Y. C. Wang, M. J. Fu, H. Wu, Y. W. Tian, W. X. Qiu, S. Z. Su, G. H. Xi An Jiao Tong Univ Shaanxi Key Lab Adv Nucl Energy & Technol Xian 710049 Peoples R China Xi An Jiao Tong Univ Dept Nucl Sci & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Nucl Power Inst China Sci & Technol Reactor Syst Design Technol Lab Chengdu Peoples R China

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure. (c) 2020 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).

关键词： Dynamic characteristics The secondary loop Turbine Condenser

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Experimental and Numerical Investigation on the Transient Vascular Thermal Response to Multi-Pulse Nd:YAG Laser

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LASERS IN SURGERY AND MEDICINE 2017年第9期49卷 852-865页

作者： Li, Dong Li, Ruohui Jia, Hao Chen, Bin Wu, Wenjuan Ying, Zhaoxia Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Med Sch Dept Dermatol Laser Treatment Ctr Xian 710049 Shaanxi Peoples R China

Background and Objective: Port wine stains (PWS) are congenital vascular malformations that progressively darken and thicken with age. Laser therapy is currently the most effective way in clinical practice for PWS. A 1,064 nm Nd:YAG laser in the near-infrared band can achieve a deeper treatment depth compared to the current widely adopted pulsed dye laser. However, because of its relatively weak absorption by blood, single-pulse Nd: YAG laser requires high energy density to cause effective vessel damage, but may inflict undesirable burning to surrounding collagen. Multi-pulse laser has great potential in clinical treatment because it needs less energy density for each pulse. This paper presented an experimental and theoretical study of the transient thermal effects of low-energy multi-pulse Nd: YAG laser on blood vessels. Study Design/Materials and Methods: In vivo experiments were performed on dorsal skin chamber. By using a high speed camera (up to 2,000 fps), the complete and dynamic thermal response of blood vessels during laser irradiation and between pulse intervals was obtained. In vitro experiment in capillary tubes and Numerical simulations by two-scale heat transfer model were also conducted to further explore the in vivo experimental findings. Results: The complete and dynamic response of blood vessels were obtained, including vessel dilation, thrombus formation, partial vessel constriction, thread-like constriction, cavitation and bubbles, and hemorrhage. Thread-like constriction is the desirable treatment end point, which will only occur after thrombus completely occludes the vessel lumen. Cavitation can cause hemorrhage when thrombus fails to occlude the vessel lumen. In vitro experiment found that vessel constriction was due to the constriction of thrombus induced by laser irradiation. Theoretical investigation revealed that the mechanism for the effective reduction of energy density by multi-pulse Nd: YAG laser was due to enhanced light absorption of

关键词： port wine stains multi-pulse Nd:YAG laser dorsal skin chamber transient thermal effects

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