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Experimental test of rectangular microchannel printed circuit heat exchanger using supercritical carbon dioxide as working fluid

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JOURNAL OF SUPERCRITICAL FLUIDS 2023年第1期200卷

作者： Zhong, Shao-geng Ren, Yan Wang, Pei-dong Wu, Wei-dong Yang, Ying-ying Yang, Qi-guo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

This study proposed a new type of printed circuit heat exchanger with rectangular microchannels and established a test platform with supercritical carbon dioxide as working fluid. The heat transfer and pressure drop of the test sample were tested, and the experiments considered inlet temperature ranges of 335.0-338.9 K and 316.1-339.1 K for the hot and cold sides, respectively. The results revealed that hot-side inlet temperature had the most significant effect on the heat transfer rate and thermal performance. With a 10.3% increase in the hot-side inlet temperature, the heat transfer rate increased by 89.0%, and the thermal performance decreased by 17.7%. The test sample effectiveness was most significantly affected by the cold-side inlet temperature, and it increased by 23.3% as the cold-side inlet temperature increased by 5.9%. The effectiveness increased to 0.96 with an increase in the cold-side inlet temperature to 339.1 K.

关键词： Supercritical carbon dioxide Printed circuit heat exchanger Rectangular microchannel flow and heat transfer Effectiveness

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Investigation of the aerodynamic characteristics of horizontal axis wind turbine using an active flow control method via boundary layer suction

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RENEWABLE ENERGY 2022年第0期198卷 1032-1048页

作者： Wang, Peilin Liu, Qingsong Li, Chun Miao, Weipao Yue, Minnan Xu, Zifei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Liverpool John Moores Univ Offshore & Marine LOOM Res Inst Liverpool Logist Byrom St Liverpool L3 3AF England

The boundary layer suction (BLS) has the merit of effectively suppressing the formation and development of separation vortices by removing low-momentum fluid occurs on the leading-edge of airfoil suction surface. The present paper numerically investigates the impacts of BLS on the aerodynamic performance of a horizontal axis wind turbine (HAWT). First, the dynamic mode decomposition method is adopted to gain an insight into the improvement mechanism of BLS control by analyzing the flow patterns of a two-dimensional S809 airfoil. Subsequently, the BLS is arranged on a NREL Phase VI reference turbine to study the power increment and flow field characteristics, and the effects of different working angles alpha s and momentum coefficients C mu are investigated at different tip speed ratios (TSRs). The results indicate that the use of BLS control can increase the pressure difference between the suction surface and the pressure surface, raise the peak negative pressure at the leading edge and shift the airfoil flow separation point backwards, and thus effectively enhance the stability of the flow field. Furthermore, the BLS control can significantly improve the power extraction at low to medium TSR if this active device is appropriately implemented on the HAWT.

关键词： Aerodynamic performance HAWT Computational fluid dynamics Active control Boundary layer suction

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An ultrasound-based monitoring of kaolinite flocculent settling processes

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APPLIED ACOUSTICS 2023年第1期203卷

作者： Tian, Chang Zheng, Songlin Su, Mingxu Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

In order to implement real-time monitoring of flocculent settling processes, an ultrasonic method based on the ECAH model was proposed and studied, particularly by considering the influence of particle irreg-ularity on sound attenuation. Numerical simulations were conducted to evaluate the influence of critical physical parameters' variation on the attenuation coefficient. Meanwhile, an integrated experimental system including ultrasonic measurement, interface settling velocity measurement, microscopic imaging and online sampling methods was established. The experiments of kaolinite particle suspensions with four different initial mass concentrations were carried out, and the phenomenon of flocculation and set-tling was observed accordingly. The duration of each settling stage and its change rate were analyzed simultaneously by both the interface settling velocity and ultrasonic attenuation coefficient. The analysis results show that for the same flocculent settling stage, the relative deviation of duration obtained by two methods above were 0%, 7.32%,-10.57%, 1.62% and 1.63%, respectively. The mechanisms and character-istics of each stage in the precipitation process were discussed in detail. At the same time, the volume concentrations obtained by ultrasonic method were compared with the results of weighing after on-line sampling. The deviations under the four initial mass concentrations were 18.6%, 12.1%, 11.0% and 13.2% respectively. The correlation between the process of flocculation and ultrasonic parameters was established accordingly, which provided data support for the application of ultrasonic technique to the online detection of kaolinite particle flocculent settling processes.(c) 2022 Elsevier Ltd. All rights reserved.

关键词： Ultrasound Attenuation Particles flocculent settling Concentration

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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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Experimental investigation on the performance of an ethane loop heat pipe with different line lengths based on pulse tube refrigerator

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JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY 2022年第8期147卷 5225-5235页

作者： Chen, Beibei Chen, Xi Xiang, Jiajia Xie, Rongjian Wu, Yinong Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Chinese Acad Sci Shanghai Inst Tech Phys 500 Yutian Rd Shanghai 200083 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer 516 Jungong Rd Shanghai 200093 Peoples R China

The loop heat pipe is a passive high-efficiency two-phase transfer device. To study the effects of the liquid and vapor line lengths on the performance of ethane loop heat pipe (ELHP), a performance test system has been set up based on a pulse tube refrigerator (PTR). The lengths of liquid line (LL) and vapor line (VL) of the ELHP are changed in this test system. The LL length is set as 180 mm, 500 mm, 800 mm, 1100 mm and 1500 mm, respectively, when the VL length is 500 mm. In addition, the VL length is set as 800 mm, 1100 mm, and 1500 mm, respectively, as the LL length is 500 mm. The thermal performances of ELHP including startup performance, thermal resistance and temperature difference are investigated in detail under 170 similar to 240 K temperature regions. The experiment results show that the lengths of LL have an important effect on the startup performance when the heat load (HL) of the ELHP is 0 W. The shorter the LL length is, the easier the startup is at 0 W HL. When the LL length is longer, the ELHP is more stable and the temperature oscillation is smaller. The effect of the VL length on the ELHP startup performance is the same as that of the LL length. Due to the thermophysical properties of ethane, the ELHP in the 240 K temperature region has the best performance.

关键词： Ethane loop heat pipe Liquid line Vapor line Startup Thermal resistance

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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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Effect of stress on corrosion behavior of martensitic and austenitic steels in supercritical carbon dioxide at 550?C and 20 MPa

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JOURNAL OF SUPERCRITICAL FLUIDS 2023年 192卷

作者： Yang, Yingying Mao, Shijie Yang, Qiguo Xu, Ziyuan Ren, Yan Wu, Weidong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Corrosion of alloys in supercritical carbon dioxide (S-CO2) Brayton cycle power generation systems is a critical issue. In this study, we investigated the corrosion behaviors of martensitic AISI 616 and austenitic AISI 304 exposed to S-CO2 at 550 degrees C and 20 MPa. The effect of stress loading on the corrosion behavior was studied. A 9 mu m-thick double-layer oxide with an outer layer of Fe3O4 and an inner layer of (Fe, Cr)-rich oxide was formed on the surface of the AISI 616. When stress was applied, the oxide layer thickness increased significantly to 15 mu m. Stress loading thus promoted carbon deposition, accelerated the oxidation rate, and increased oxide thickness. AISI 304 generated a monolayer of (Fe, Cr)-rich oxide that was much thinner than that of AISI 616 owing to its high Cr content. In addition, the effect of stress on the corrosion of AISI 304 was weaker than that of AISI 616.

关键词： Supercritical carbon dioxide Brayton cycle Stress corrosion Steel High -temperature corrosion Oxidation

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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...

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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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