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SSRN 2022年

作者： Zeng, Pingchao Dou, Binlin Zhang, Hua Wang, Yadong Wu, Kai Zhao, Longfei Chen, Haisheng Xu, Yujie School of Energy and Power Engineering Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China

For highly efficient transformation and utilization of waste cooking oil, a new method for hydrogen production by indirect and auto-thermal chemical looping steam reforming (CLSR) of waste cooking oil (WCO) was developed in this work. In conventional and direct CLSR using WCO at a temperature of 650 °C, gas production, hydrogen selectivity, and fuel conversion were low due to the insufficient amount of reducing Ni and heating. Thus, the reactor temperature was increased to 750 °C to pyrolyze enough reducing gas to reduce OCs. Although 84% WCO conversion and 88% hydrogen selectivity were obtained, the OCs deactivated at the last 15 minutes due to the high-temperature sintering of the reduced Ni particles. On this basis, a new type of indirect CLSR with high-temperature steam-assisted pyrolysis of WCO in a two-stages fixed-bed reactor with high stability was developed, which fitted WCO feeding and avoided OCs sintering. The experimental results show that about 90% WCO conversion and about 89% hydrogen selectivity were obtained in indirect CLSR, and the highest hydrogen yield and selectivity were obtained under the conditions of upper pyrolysis temperature of 800 ℃ with a lower CLSR temperature of 600 ℃ and S/C=4.12. In addition, the effect of in-situ CO 2 capture on indirect CLSR achieves the feasibility of hydrogen production and minus carbon emissions. The multiple cycles experiments of indirect CLSR obtained about 90% hydrogen selectivity and fuel conversion, close to 0 CH 4 selectivity, and 24%~26% steam conversion. © 2022, The Authors. All rights reserved.

关键词： Hydrogen production

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The Enriched-Embedded Discrete Fracture Model (Nedfm) for Fluid flow in Fractured Porous Media

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SSRN 2023年

作者： Jiao, Kaituo Han, Dongxu Chen, Yujie Bai, Bofeng Yu, Bo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development Beijing Institute of Petrochemical Technology Beijing102617 China

The embedded discrete fracture model (EDFM) is widely adopted for fluid flow in fractured porous media, but it cannot be employed for blocking fractures due to the assumption of symmetric and linear pressure distribution around fractures. To improve it, this work presents a novel numerical framework named the enriched-embedded discrete fracture model (nEDFM). It is based on the non-conforming grid and discretized by the mass-conservative finite volume method. Attractively, the nEDFM applies to both conductive and blocking fractures, as well as isotropic and anisotropic matrix permeability, while maintaining a low computational cost. The local shape function, which introduces two enriched degrees of freedom for every fracture cell, is developed to model the discontinuities of pressure and its gradient on two sides of the fracture. Correspondingly, two equations for coupling the matrix and reduced fracture are supplemented to close the system and improve the accuracy of mass exchange between the matrix and fracture. The performance of nEDFM is compared with the classical EDFM and projection-based EDFM (pEDFM). The results show that the nEDFM outperforms the EDFM for conductive fractures and can obtain better pressure distribution inside blocking fractures than the pEDFM. For anisotropic matrix permeability with conductive or blocking fractures, the nEDFM can get solutions comparable to those obtained by the reference solution. Hence, the nEDFM is an accurate and flexible method for fluid flow simulation in fractured porous media. © 2023, The Authors. All rights reserved.

关键词： Fracture

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Study in steam-water two-phase flow heat transfer at high mass velocity of flow in vertical helical coiled tube

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2008年第3期29卷 423-428页

作者： Guo, Meng Zhao, Liang Mao, Yu-Fei Zhen, Fei-Qiang Zhang, Wen-Bin Guo, Lie-Jin Peng, Xiao-Feng State Key Lab. of Multiphase Flow in Power Engineering Xi'an 710049 China

Experiments were conducted to further understand the heat transfer in two-phase flow in vertical helically-coiled tubes. The experiments covered a wide range of pressure 8.0-15.0 MPa, mass flow rate 2500-4000 kg/(m2s), heat flux 200-800 kW/m2. The experimental segment is 2.335 meter long and made by φ14 × 2 mm steel tube. The diameter ratio D/d is 30.1. Through analyzing the influence of heat flux, mass velocity on average heat transfer coefficient, we acknowledge the activities of nucleate boiling and forced convection two mechanism on steam-water two-phase heat transfer in helical coils tubes at high mass flow rate. The average and local heat transfer coefficient correlations were obtained. At high mass flow rate conditions, the effect of heat transfer in the steam-water two-phase flow in helically coils is inclined to that of straight tube at same conditions and the results are compared.

关键词： Heat exchangers

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Experimental Study on flow Patterns in Narrow Rectangular Channels

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SSRN 2022年

作者： Lv, Xindi Zhang, Dalin Song, Gongle Su, Guanghui Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China

Plate fuel elements are commonly used in compact nuclear reactors due to the advantages of high fuel consumption. In this paper, the two-phase flow pattern in the coolant channel of plate fuel elements, i.e. the rectangular narrow channel was studied. Visualization flow pattern experiments of upward steam-water two-phase flow in narrow rectangular channels, 745mm long and 67mm wide with gap widths of 1.3mm and 1.9mm, were investigated. The experiments were performed in the conditions of pressure ranging from 1 to 2MPa, mass flow rate ranging from 200 to 1500kg/(m2 ⋅s), inlet subcooling ranging from 20~100°C and tilt angle ranging from 0~ 45°. Three flow patterns, consisting of bubble flow, churn flow and annular flow, were obtained in a wide range of thermal parameters. flow patterns maps were plotted and the influences of pressure, mass flow rate, inlet subcooling, channel gap and tilt angle on the flow pattern transformation of narrow rectangular channel were studied. This study is of great significance for investigating the subsequent heat transfer process of two-phase flow in compact nuclear reactors. © 2022, The Authors. All rights reserved.

关键词： Two phase flow

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Comparison of Gelatinous and Calcined Magnesia Supported Ni or/And Co-Based Catalysts for Aqueous Bioglycerol Phase Reforming

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SSRN 2021年

作者： Liu, Dashuai Dou, Binlin Zhang, Hua Wu, Kai Zhao, Longfei Zeng, Pingchao Chen, Haisheng Xu, Yujie School of Energy and Power Engineering Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China

In this study, glycerol aqueous phase reforming was carried out in a batch reactor. The gases produced were H2, CO, CH4, and CO2 during the experiment. The catalysts used included Ni or/and Co catalysts supported by MgO. Meanwhile, two different MgO supporters were prepared by the sol-gel method and calcining method, and the active metal was added by an initial wet impregnation (IWI) method. The catalysts were characterized by BET, BJH, TEM, and XRD. In order to achieve the purpose of comparison, the activity of different types of catalysts was tested under similar conditions. It was found that the amount of hydrogen produced by the catalyst containing gelatinous MgO supporter is more than 1.5 times that of other catalysts, and the Ni-Co-MgO had the best catalytic effect among the same types of catalysts. The activity of the Ni-Co-MgO catalyst was tested under different temperatures, concentrations, and CaO conditions. We found that Ni-Co bimetallic catalyst supported on gelatinous MgO has the best highest gas production, while the catalyst containing calcined MgO support usually has a better hydrogen selectivity. Through the stability study of the Ni-Co-MgO catalyst, we found that the bimetallic catalyst supported by gelatinous MgO support has better catalytic stability. © 2021, The Authors. All rights reserved.

关键词： Sol-gel process

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Characteristics of Bubble Dynamic Behavior on the Surface of Photoelectrode Under the Influence of a Vertical Magnetic Field

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SSRN 2023年

作者： Feng, Yuyang Wang, Yechun Zhang, Bo Cao, Zhenshan Liu, Miaomiao Zhen, Canghao Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xinjin Weihua Institute of Clean Energy Research Nanhai District Guangdong Province Foshan City China

The magnetohydrodynamic (MHD) flow around the bubble induced by the Lorentz force owing to the applied magnetic field significantly affects the behavioral characteristics of the bubble on the electrode surface. However, the mechanism of the impact of a magnetic field perpendicular to the electrode on the dynamic behavior of bubbles remains unclear. In this study, the evolution law of a single oxygen bubble on the surface of a TiO2 photoelectrode under the influence of a vertical magnetic field with different magnetic induction intensities was investigated. The vertical magnetic field effectively promoted the rapid detachment of bubbles from the electrode surface, and greatly improved the gas evolution efficiency. The mass transfer was dominated by single-phase free convection during bubble evolution. Under the influence of the vertical magnetic field, the mass transfer coefficient near the electrode was enhanced, and the adverse effects of bubbles on mass transfer were counteracted when they entered the reaction-controlled growth phase. The further multiphysics simulation found that the MHD convection decreased the local supersaturation of reaction product oxygen molecules near the electrode, thereby reducing concentration overpotential and increasing the reaction rate. This study provides an experimental and theoretical basis for promoting the bubble detachment and the reaction rate on the gas evolving electrode surface during photoelectrochemical water splitting. © 2023, The Authors. All rights reserved.

关键词： Efficiency

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RECENT ADVANCES OF SURFACE WETTABILITY EFFECT ON flow BOILING HEAT TRANSFER PERFORMANCE

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Frontiers in Heat and Mass Transfer 2021年 17卷

作者： Cao, Shuang Yang, Hui Zhao, Luxing Wang, Tao Xie, Jian School of Energy and Power Engineering Zhengzhou University of Light Industry Zhengzhou450002 China Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University Beijing102206 China

flow boiling heat transfer is an effective way to fulfill the energy transfer. The wettability of boiling surface influences the liquid spreading ability and the growth, departure, and release frequency of bubbles, which determines the heat transfer performance. According to the wettability and combination forms, boiling surface are classified into weak wetting surface, strong wetting surface, and heterogeneous wetting surface. Fabricating by physical, chemical method or coating the original surface with a layer of low surface energy, the weak wetting surface has more effective activation point and nucleation center density to improve heat transfer performance at low heat flux. The strong wetting surface always formed by physical or chemical treatment to enhance the rapid rewetting of the wall surface. It has a smaller bubble separation diameter, higher separation frequency and higher CHF. The heterogeneous wetting surface, having the synthetic effects of the strong and weak surface wettabilities, is a hot issue of recent study. But its composition and heat transfer enhancement mechanism are very complicated which need to study thoroughly. Furthermore, the intelligent wetting surface, having the dynamics wettability function, is also briefly analyzed in this paper. Despite the advances in this aspect, the boiling surfaces can be further optimized by fabricate effective wettability to achieve a strong stability, high heat transfer performance and realize the synergistic effect of flow pattern and heat transfer. © 2021, Global Digital Central. All rights reserved.

关键词： Wetting

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Thermionic Conversion Performance Analysis of the Single-Cell Thermionic Fuel Element Based on Froba-Thermion Code

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SSRN 2022年

作者： Lu, Kailin Yao, Hao He, Yanan Wu, Yingwei Zhang, Jing Liao, Haoyu Su, Guanghui H. Qiu, Suizheng School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China

The thermionic conversion performance of the single-cell thermionic fuel element (TFE) is influenced by fuel mass transfer and other parameters. With the consideration of current flow and heat transfer, the thermionic conversion model and the modified heat transfer model were implemented in FROBA-THERMION. Afterward, both implemented models were verified by comparing with experiments or KATET calculation results. Further, a steady-state performance simulation of the single-cell TFE was carried out. The results indicate that the thermionic conversion efficiency will be decreased due to the emitter temperature flattening caused by fuel mass transfer. In addition, the influence of several key parameters on thermionic conversion efficiency and measures to improve the thermionic conversion efficiency were analyzed. © 2022, The Authors. All rights reserved.

关键词： Mass transfer

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Experimental Study of an Aluminum Based Three-Dimensional Thermosyphon Heat Sink with Microscale Enhancement Structure

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SSRN 2024年

作者： Yang, Xiaoping Bu, Shichao Jiang, Zhuye Zhou, Yao Sun, Zhen Zhang, Yonghai Wei, Jinjia School of Chemical Engineering and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Mobile Network and Mobile Multimedia Technology ZTE Corporation Hillsides China

Heat dissipation is a significant factor limiting the advancement of electronics. Currently, air cooling remains the most widely used method for heat dissipation due to the advantages of low-cost and easy-maintenance. However, the traditional air-cooling method based on all-solid heat sink fails to meet the fast development in thermal power of electronics because its limitation in area expansion by only solid fins. In this study, an aluminum based three-dimensional thermosyphon (3D-TS) coupling boiling-condensation heat transfer and forced air cooling is proposed to overcome the limitation of conventional air cooling methods. Meanwhile, micro pin-fins structure is used to enhance the boiling heat transfer as well as the performance of the 3D-TS. Using the environmentally friendly refrigerant R1233zd(E) as working fluid, the performance of the 3D-TS is experimentally studied and analyzed under different air volume flow rates. The results show that the total thermal resistance decreases firstly and then increases with the heating power, which is mainly dominated by the boiling mode on the substrate. Moreover, the micro pin-fins greatly enhances the boiling heat transfer on the substrate of the 3D-TS, which enables the 3D-TS to reach a minimum thermal resistance of 0.075 K/W and a maximum thermal dissipating power of 650 W with the temperature of the heating source below 85 °C. The 3D-TS proposed in this work is able to meet the cooling requirements of most high-performance chips. This paper provides valuable reference and guidance for the design and optimization of the phase-change devices. © 2024, The Authors. All rights reserved.

关键词： Aluminum

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Numerical investigation on transport characteristic of air breathing direct methanol fuel cell

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Huagong Xuebao/CIESC Journal 2011年第SUPPL. 1期62卷 66-71页

作者： Miao, Zheng Zou, Jinqiang He, Yaling Liu, Zeng State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 Shaanxi China

A two-dimensional two-phase non-isothermal mass transport model is developed in this paper for the air breathing direct methanol fuel cell(DMFC). The self-made computer code is used to simulate the heat and mass transport characteristic which is coupled with electro-chemical reactions. The effects of temperature of the inlet methanol solution, temperature of the air, and the feeding concentration of methanol on the performance of the fuel cell are investigated. The numerical results show that the cell performance can be enhanced at a higher temperature of the inlet methanol solution and the air. Cell performance at the higher cell current densities can be improved with a higher feeding concentration of methanol. © All Rights Reserved.

关键词： Heat transfer

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