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SSRN 2024年

作者： Zhang, Tianjiao Su, Mengyang Zhang, Hua Liu, Chuang Ouyang, Xinping School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China Key Laboratory of Thermo-Fluid Science and Engineering Ministry of Education Xi’an Jiaotong University Xi’an710049 China

Slit fin-and-tube heat exchangers are extensively utilized in industry, and optimizing the fin structure is conducive for improving energy efficiency and reducing energy losses. Therefore, a heat exchanger featuring trapezoidal slit fins was proposed in this study. To determine the structure of the slit fins, physical and mathematical models of the heat exchanger with a fin spacing Fp of 2.65 mm were established. We used a numerical simulation to investigate the structural parameters of the fin-and-tube heat exchanger, including the slit height Sh, slit width Sw, transverse tube spacing Pt, and longitudinal tube spacing Pl. Based on the simulation results, the effects of the four structural parameters on the comprehensive performance were evaluated. Additionally, the optimal parameter combination was determined through an orthogonal test, resulting in the following values: Sh = 1.47 mm, Sw = 4 mm, Pt = 42 mm, and Pl = 27.5 mm. This study provides significant theoretical and practical guidance. © 2024, The Authors. All rights reserved.

关键词： Energy dissipation

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Large eddy simulation on the wake characteristics of linearly stratified flow past a sphere

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Scientific Reports 2025年第1期15卷 1-13页

作者： Xia, Tianci Wei, Na Shi, Liuliu School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093 China Key Laboratory of Power Machinery and Engineering of Ministry of Education Shanghai Jiao Tong University Shanghai 200240 China

In this study, Large Eddy Simulation (LES) has been employed to examine the influence of the Froude number (Fr) on the linearly stratified wake and internal waves behind a sphere at a subcritical Reynolds number of Re = 3700. Six distinct sets of models with varying Fr (Fr = 0.05, 0.25, 0.5, 1, 2, ∞) have been chosen to establish density linear stratification through the use of a User Defined Function (UDF). The analysis focuses on the impact of stratification on wake characteristics, velocity distribution, and the structure of internal waves within stratified flow. It is evident that density stratification plays a pivotal role in shaping wake structure. Notably, in stratified flows, wakes exhibit unique characteristics including the generation of internal waves, suppression of vertical velocity, and the emergence of oscillating wake patterns. The study reveals that a decrease in the Froude number leads to heightened vertical suppression of the wake and increased anisotropy of the velocity distribution. Furthermore, as the Froude number ascends from 0.05 to 2, the wake undergoes a transition from quasi-two-dimensional vortex shedding to three-dimensional turbulence. © The Author(s) 2025.

关键词： Froude number Internal wave Linearly stratified flow Wake

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Study of flow Pattern Transition Criterion and heat transfer Characteristics in Vertical Rectangular Narrow Channel for Steam heating

SSRN

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SSRN 2023年

作者： Gu, Shengjie Tao, Leren Jin, Cheng Ju, Yiwei Zhao, Xiefei School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power and Engineering University of Shanghai for Science and Technology Shanghai200093 China

To clarify the heat transfer characteristics of flow boiling in a narrow vertical rectangular channel at each stage and optimise the performance of the heat exchanger, an experimental study of the flow pattern and local heat transfer characteristics in a narrow vertical rectangular channel of steam heating with dimensions of 1400 mm × 250 mm × 2.75 mm (l × w × s) was carried out using deionized water as the working medium. Based on the mechanical model and the empirical formulas of the researchers, the preliminary derivation of the flow pattern transition criterion in the vertical rectangular narrow channel for steam heating is obtained. The effects of inlet temperature, mass flux and heating power on the local heat transfer characteristics were analyzed in conjunction with the flow patterns, and based on the parametric analysis of the experimental data, a new flow boiling heat transfer correlation formula was obtained which applies to the experimental conditions in this paper. The results show that the increase in inlet temperature has a positive effect on the nucleate boiling section, while the degree of effect on the local heat transfer coefficient is minimal after entering the churn flow phases. The increase in mass flux decreases the local heat transfer coefficient in the nuclear state boiling stage and enhances the local heat transfer coefficient in the evaporation zone of liquid film flow. The peak of the local heat transfer coefficient shows a tendency to shift to the left as the heating power increases. The new heat transfer correlation equation can well predict the local heat transfer coefficient of flow boiling in a vertical rectangular narrow channel heated by steam in this experimental condition. © 2023, The Authors. All rights reserved.

关键词： flow patterns

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Sensitively detection of ascorbic acid in orange samples with ionic liquid functionalized carbon dots and lanthanide complexes

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DYES AND PIGMENTS 2024年 227卷

作者： Li, Ying Xia, Ji-Ji Lu, Jia-Zhen Wang, Zi-Long Wang, Mi-Tang Univ Shanghai Sci & Technol Sch Mat & Chem Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

In the food industry, ascorbic acid (AA) is widely used as an antioxidant. However, the concentration of AA is influenced by various factors, including temperature, time, and pH value during food preparation and storage, leading to its instability in content. This makes the accurate detection of AA content particularly important. Precise determination of AA content in food and pharmaceuticals is crucial for ensuring the adequate intake of essential vitamins and maintaining good health. Herein, we have developed a successful preparation method of an imidazole-based ionic liquid functionalized CDs hybrids APM-CDs. A novel photo functional hybrid probe Eu3+@APM-CDs was obtained via an ion-exchange reaction between APM-CDs and lanthanide complex Eu (DPA)3. The obtained hybrid probe was extensively characterized in detail. What's more, the results show that the fluorescent intensity of Eu3+@APM-CDs has a good linear response to AA concentrations in the range of 25-500 mu M (R-2 = 0.99), with a detection limit of 80 nM. The fluorescence probe demonstrates good selectivity and sensitivity toward AA and has the potential for significant application in AA detection by simplifying procedures and reducing interference from impurities.

关键词： Lanthanide probe Ionic liquid C-dots Fluorescence sensor Ascorbic acid

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Optimization study on airfoil aerodynamic performance with local indentation treatment based on drainage characteristics of dolphin fluke

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JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY 2024年第4期16卷

作者： Huang, Shengxian Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Natl Key Lab Sci & Technol Aerodynam Design & Res Xian 710072 Peoples R China

Enhancing the aerodynamic performance of airfoils is the key to optimizing the energy harvesting efficiency of rotating machinery such as wind turbines. Motivated by the bowl-shaped outline of the dolphin's fluke during the propulsion process, this paper proposes a local indentation method that generates a concave region on the pressure surface of the airfoil. The NACA 0018 airfoil is selected as the reference airfoil, and two types of treatments are applied near the trailing edge point: rigid deformation and flexible deformation. Based on the grid quantity independence and experimental results validation, the results demonstrate that compared with the original airfoil, the local indentation method can modify the pressure distribution of the indentation section itself and optimize the airfoil's overall aerodynamic performance. The lift coefficient of the whole airfoil increases gradually with the rise in the indentation depth and reaches a stable value eventually. Quantitative results reveal that when the indentation depth D = 0.020c, the lift coefficient of the whole airfoil can increase by up to 26.27%;when the indentation depth D = 0.010c, the airfoil's lift-to-drag ratio reaches the maximum, which is 16.39% higher than that of the original airfoil. When replacing the rigid indentation section with a flexible medium, the fluid flowing over the pressure surface interacts with the flexible medium. The method of local indentation proposed in this paper can provide valuable reference for optimizing the aerodynamic profile of airfoils and improving the energy harvesting efficiency of wind turbines.

关键词： Airfoils

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Depth from Defocus Technique for High Number Densities and Non-spherical Particles

arXiv

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arXiv 2024年

作者： Xu, Rixin Huang, Zuojie Gong, Wenchao Zhou, Wu Tropea, Cameron School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer for Power Engineering University of Shanghai for Science and Technology Shanghai China Institute for Fluid Mechanics and Aerodynamics Technical University of Darmstadt Darmstadt Germany

The Depth from Defocus (DFD) imaging technique for measuring the size and number concentration of particles in a dispersed two-phase flow has up to now been restricted to relatively sparse particle densities and to identifying only spherical particles. The present study examines two advancements to the technique, widening its range of application significantly. The first advancement introduces an image processing procedure which can identify and size particle images which are overlapping. This increases the tolerable number concentration of particles which can be identified and processed within the measurement volume. The second advancement explores the possibility of determining the size and position of non-spherical particles within an observation volume. Both advancements build on recent theoretical work, utilizing not only the gray level of the blurred, out-of-focus images, but also the gradient of the gray level normal to the nominal particle or particle ensemble contour. This gray-level gradient is used to estimate the width of the blur kernel, which is assumed to remain Gaussian. These enhancements are experimentally validated using a dedicated apparatus in which particles of known size, shape and degree of overlapping images can be systematically varied. This experimental setup provides benchmark data to quantify the accuracy and limitations of the processing algorithms. © 2024, CC BY.

关键词： Spheres

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Exploration of the Responsiveness of the Atomization Field in a Centrifugal Nozzle to Variations in Inlet Pressure

SSRN

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SSRN 2023年

作者： Xu, Wen Yang, Jianwen Yang, Bin Wang, Ying Shanghai Key Laboratory of Multiphase Flow and Heat Transfer of Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Xi’an Aerospace Propulsion Institute Xi’an710100 China

As the crucial atomization unit in the propellant supply system for liquid rocket engines, the centrifugal nozzle's atomization performance is of paramount importance. However, due to flow oscillations within the propellant supply system, the resulting spray from nozzle atomization tends to oscillate, adversely impacting fuel atomization efficiency. This paper employs a VOF-to-DPM multiphase flow model to simulate the nozzle's atomization field under different inlet pressures, which is subsequently compared with experimental results. Next, the UDF is used to introduce pressure pulsation sources with varying frequency sizes at the nozzle inlet, from which the following conclusions are drawn: (1) The numerical simulation-derived atomization angle of the nozzle under different inlet pressures slightly deviates below the experimental value, but consistently maintains a similar trend, with errors not exceeding 5%;(2) Under constant inlet pressure, the nozzle's atomization field exhibits a stable, smooth, hollow cone liquid film formation, and particle droplets produced by liquid film atomization coalesce at the hollow cone's lower end;(3) When pressure pulsations with diverse frequencies and magnitudes are loaded at the nozzle inlet, the atomization field undergoes varying degrees of oscillation. When f = 100 Hz, the hollow cone liquid film disappears completely after undergoing initial formation during a pulsation cycle, and the atomized particles' number experiences the most significant change relative to constant inlet pressure. When f = 400 Hz, the broken droplets gradually reform the hollow cone liquid film within a pulsation period and maintain its form but undergo subsequent breaking. When f = 800 Hz, there is no apparent alteration in the shape of the hollow cone liquid film or total particle count during a pulsation cycle. However, the liquid film's surface appears uneven, showing wavy water marks. © 2023, The Authors. All rights reserved.

关键词： Atomization

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Novel Matching Strategy for the Coupling of heat Flux in Furnace Side and CO_(2)Temperature in Tube Side to Control the Cooling Wall Temperatures

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Journal of Thermal Science 2021年第4期30卷 1251-1267页

作者： LIU Chao MIAO Zheng XU Jinliang XU Zeyu LI Mingjia Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijing 102206China Key Laboratory of Power Station Energy Transfer Conversion and System North China Electric Power UniversityMinistry of EducationBeijing 102206China Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy&Power EngineeringXi’an Jiaotong UniversityXi’an 710049China

Required by the supercritical carbon dioxide(s CO_(2))coal-fired power cycle,s CO_(2)entering a boiler has a high temperature and can cause overheating of *** eliminate the pressure drop penalty effect,the s CO_(2)boiler consists of several modules,each having different heat flux received from the furnace side(q)and different CO_(2)temperature in the cooling wall tube(T_f).We aim to search for the best matching strategy coupling furnace side and tube side to obtain the lowest temperature of *** theoretically analyzing the wall temperature influenced by q,T_f and a comprehensive thermal resistance C,two matching methods are introduced:the heat flux-temperature matching(HTM)which matches higher q with lower T_f,and the heat flux-heat flux matching(HHM)that matches higher q with higher allowable-heat-flux at the temperature limit of *** is a conventional method but HHM is newly proposed *** show that,if C is identical for different modules,the two methods coincide;otherwise,HHM is *** a s CO_(2)boiler driving 1000 MWe power plant,smaller cooling wall temperatures are obtained by HHM than *** on HHM,the mid-partition wall,heat transfer enhancement,and downward flow are comprehensively used,decreasing the wall temperature significantly.

关键词： sCO_(2)power cycle sCO_(2)modular boiler cooling wall temperature allowable heat flux matching strategy

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Fiber optic probe sensor for supercritical fluid heat transfer measurement 2

Fiber optic probe sensor for supercritical fluid heat transf...

引用

2nd International Conference on Sensors and Information Technology, ICSI 2022

作者： Cheng, Yiwei He, Xiaotian Xu, Jinliang Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University 2 Beinong Road Changping District Beijing China

ISBN: (纸本)9781510654860

To improve the efficiency of power generation systems, the boiling-like phenomenon in supercritical fluid heat transfer has attracted much attention. However, traditional tapered fiber optic probes are not suitable for supercritical fluid two-phase-like distribution detection. In this paper, a fiber optic probe sensor with a flat end face that can continuously measure the refractive index and density of fluids is developed and tested using water, CO2, and ethanol. The average relative error of density measurement is less than 0.1 %. Applied to a supercritical fluid pool heat transfer experimental system, the probe's signal coincided with the visualization phenomenon very well. The frequency of gas-like film detachment from the surface of the heating wire could be accurately measured using the probe. © 2022 SPIE.

关键词： Supercritical fluids

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Effects of the frequency conversion characteristics of fan and pump on the performance of heat pump driven humidification-dehumidification wastewater treatment system

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heat AND MASS transfer 2022年第12期58卷 2067-2083页

作者： Zhang, Huichen Liu, Jianhua Jiang, Linlin Zhang, Liang Wu, Qingqing Xu, Xiaojin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Nantong Vocat Univ Nantong 226007 Jiangsu Peoples R China Shanghai Highly Grp Co Ltd Shanghai 201206 Peoples R China CSCI Res Inst 704 Shanghai 200031 Peoples R China

An experimental study on use of humidification-dehumidification (HDH) technology for treating chemical milling wastewater containing high concentrations of sodium hydroxide and sodium aluminate has been carried out. heat pump is introduced to simultaneously supply cooling and heating loads of the HDH system. A parametric study is conducted to investigate influence of operational parameters including frequency conversion characteristics of circulating fan and pump on system performance. Performance parameters including pure water production amount (PWPA), pure water recovery rate (PWRR) and gain output ratio (GOR) are analyzed. Results indicate working frequency of pump and fan is not as high as possible, there is an optimal value. With frequency conversion of fan increases, PWPA and PWRR are increased, GOR shows a trend of first increasing and then decreasing, the optimal value of circulated air mass flow rate is 0.44 kg/s. With frequency conversion of pump increases, PWPA and GOR are increased, PWRR is decreased, the optimal value of inlet wastewater mass flow rate is 0.465 kg/s. When system is operating under optimal parameters, PWPA is 9.77 kg/h, PWRR is 0.58% and GOR is 0.781. Compare the indicators before and after treatment, pH, SS, COD, NH4-N and TP of purified water is 9.2, 4 mg/L, 53.2 mg/L, 0.028 mg/L, 0.278 mg/L, respectively. All these parameters decrease 31.9%, 97.6%, 97.5%, 77. 8%, 94.8%, respectively. Although the purified water has not yet reached the direct discharge standard or reclaimed water reuse standard, but HDH method shows feasible in the separation of highly corrosive solutions.

关键词： Pumps

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