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Numerical Study on Aerodynamic Performance of Different Forms of Adaptive Blades for Vertical Axis Wind Turbines

ENERGIES 2021年第4期14卷 880页

作者： Hou, Longfeng Shen, Sheng Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Shandong Prov Key Lab Ocean Engn Qingdao 266100 Peoples R China

The wind energy exploitation technique has been developed very quickly in recent years. The vertical axis wind turbine is a hot research domain due to several advantages: low noise, flexible for installation, ease of maintenance, great safety and credibility, etc. The aerodynamic performances of different forms of airfoils including an active deformation airfoil and a fluid-solid coupling passive airfoil with two-dimensional (2D) and three-dimensional (3D) cases have been investigated numerically in this paper. Firstly, the aerodynamic performances of the airfoils with the maximum deformation amplitudes of their cambers which are 3%, 5% and 7% of the chord length have been discussed, respectively, with the angles of attack in the range of 0 degrees and 20 degrees. Secondly, for the angle of attack set at 18 degrees, the two-way fluid-solid coupling simulations with the Young's Modulus of 1 Mpa and 2 Mpa have also been investigated. Results show that: (1) for the pseudo 3D and real 3D single active deformation airfoil cases, the lift coefficients increase as the maximum deformation amplitudes augment from 3% to 7% of the chord length at the same angle of attack. With the same maximum deformation amplitude, when the angles of attack increase from 0 degrees to 20 degrees, the lift coefficients which increase firstly and then decrease are bigger than that of the original NACA0012 airfoil. When the maximum deformation amplitude of the pseudo 3D airfoil reaches 5% of the chord length, a relatively good aerodynamic performance with better inhibition effect of vortex generation can be obtained. The 3D vortex distribution demonstrates that the deformable airfoil has a better vortex generation controlling effect at the middle cross-section along the spanwise direction than the non-deformable airfoil. (2) From the aspect of fluid-solid coupling, the lift increases and the drag decreases so that the lift to drag ratio has a big improvement when the Young's Modulus is equal to 1

关键词： adaptive blade aerodynamic performance fluid-solid coupling vertical axis wind turbine

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Effect of hydrothermal and hydrothermal oxidation pretreatment on the physicochemical properties of biofuel pellet

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JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS 2022年 165卷

作者： Shi, Yue Zhang, Shouyu Xu, Jiaqing Cao, Zhongyao Wu, Yuxin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Tsinghua Univ Dept Thermal Engn Beijing 100084 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Dept Thermal Engn 516 Jungong Rd Shanghai 200093 Peoples R China

The effects of hydrothermal pretreatment with and without H2O2 addition on the properties of the resulted biofuel pellets prepared from cotton stalk (CS) and Chinese fir wood sawdust (WS) were mainly studied in the paper. Based on the changes of three main components (hemicellulose, cellulose and lignin) of biomass during the pretreatment process, the relaxation density, compressive strength, heating values (HVs), and combustion characteristics of the resulted pellets were analyzed to evaluate the feasibility of the utilization as biofuel pellets. The results indicate that the hydrothermal pretreatments with and without H2O2 addition are beneficial to the quality of the resulted biofuel pellets. Particularly, the hydrothermal pretreatment with H2O2 addition, namely the hydrothermal oxidation pretreatment can significantly alleviate the pretreatment severity of the highstrength biofuel pellet preparation. H2O2 addition promotes the decomposition of hemicellulose and cellulose during the pretreatment. Compared with CS, WS is more sensitive to the pretreatment, especially hydrothermal oxidation pretreatment. The crystallinity index and the cellulose content of the biomass sample both increase firstly and then decrease with the increasing pretreatment temperature. In the study, the pretreatment temperature for the biofuel pellets with the best mechanical properties is 230 degrees C for the hydrothermal process and 200 degrees C for the hydrothermal oxidation process, respectively. The HVs of the resulted biofuel pellet increases with the increasing pretreatment intensity and the suitable pretreatment can improve the combustion characteristics of the resulted biomass. The mechanical properties of the pretreated biofuel pellets were positively correlated with the crystallinity and the content of the cellulose. HVs of WS pellets is higher than CS pellets, with the better mechanical properties. The cellulose is more favorable for the improvement of the combustion properties

关键词： Biofuel pellets Hydrothermal pretreatment Hydrothermal oxidation pretreatment Mechanical property Combustion property Cellulose crystallinity

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Acoustic tomography of temperature and velocity fields by using the radial basis function and alternating direction method of multipliers

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INTERNATIONAL JOURNAL OF heat AND MASS transfer 2022年 188卷 122660-122660页

作者： Zhang, Juqi Qi, Hong Ren, Yatao Su, Mingxu Cai, Xiaoshu Harbin Inst Technol Sch Energy Sci & Engn Harbin 150001 Peoples R China Minist Ind & Informat Technol Key Lab Aerosp Thermophys Harbin 150001 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China

Considering the acoustic refraction effect, an investigation of simultaneously visualizing the temperature and velocity fields is carried out by using the combined meshfree radial basis function and alternating direction method of multipliers (RBF-ADMM). The radial basis function is introduced to recover the nullspace component. It assumes that the reconstructed fields are continuous functions according to their nature, which, therefore, adds the prior information of the continuity in the fields' reconstruction. Meanwhile, the alternating direction method of multipliers with improving anti-noise capacity is employed to iteratively resolve the inverse acoustic tomographic problem in low Mach number, which makes the parallel implementation and distributed optimization possible. Different from the traditional methods for solving boundary value problems, a fast two-point ray-tracing algorithm is introduced to trace the curved sound waves more efficiently. Proof-of-concept demonstrations including the representative temperature and aerodynamic fields are performed. For the two scenarios of two-peak and two-vortex inhomogeneous fields with 10% measurement errors, the averaged absolute errors of the reconstructed temperature fields are 120.7 K, and 39.9 K, respectively, and that of the reconstructed velocity fields are 0.24 m/s and 1.23 m/s, respectively. In addition, a data-based verification, which depicts the Karman vortex street phenomenon, is carried out to prove the ability of this method. All the results confirm the feasibility and effectiveness of the proposed RBF-ADMM in simultaneously reconstructing the temperature and velocity fields under different complicated environment. The proposed method for visualizing the arbitrary temperature and velocity fields will provide crucial input for control system such as the engines and boilers to optimize the thermal fluid and combustion process. (c) 2022 Elsevier Ltd. All rights reserved.

关键词： Acoustic tomography Radial basis function Refraction effect of sound wave Alternating direction method of multipliers Temperature measurement Velocity measurement

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Design Optimization of Boiler Tail Flue in Supercritical Carbon Dioxide power Generation System

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Mechanical engineering Science 2021年第2期3卷 9-16页

作者： Wenli YE Jinliang XU Guanglin LIU Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijingChina Key Laboratory of Power Station Energy Transfer Conversion and System North China Electric Power UniversityMinistry of EducationBeijingChina

The S-CO_(2) top-bottom combined cycle based on overlap energy utilization can lead to excessive heating area,due to the small temperature difference and the large thermal load for the heating surface at the tail of the ***,reasonable optimization indexes are needed for design *** optimization indexes include heating area and working medium pressure drop,but lower working medium pressure drop usually leads to large heating area,for example,with the increase of tube inner diameter or boiler width,the pressure drop decreases but the heating area ***,if both are used as optimization indexes,it will be difficult to choose the optimum tube inner diameter and boiler *** this paper,exergy loss analysis is used,in combination with economic analysis,the optimization index is unified to the cost per unit heat transfer of the heating *** thermal calculation and pressure drop calculation models are established for the heating surface at the tail of the *** optimized heating surface can greatly improve the economic benefit.

关键词： S-CO_(2)cycle calculation model exergy loss analysis optimization of the boiler

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Reducing the NOx emissions during NH3 oxidation with Nickel modified Fe2O3-a promising cost-effective and environmentally friendly catalyst for NH3 combustion

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COMBUSTION AND FLAME 2022年 237卷 111845-111845页

作者： Wu, Ye Mei, Jian Cai, Tianyi Wang, Wei Zhu, Hang Sun, TianLi Liu, Dong Nanjing Univ Sci & Technol Sch Energy & Power Engn MIIT Key Lab Thermal Control Elect Equipment Nanjing 210094 Peoples R China Nanjing Univ Sci & Technol Sch Energy & Power Engn Adv Combust Lab Nanjing 210094 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Ammonia is considered to be a green energy due to its carbon-free footprint, high energy density, cheap transport costs and so on. However, the problem of NOx (mainly NO/NO2) emissions especially at high temperature (>800 degrees C) inhibits the energy utilization progress of NH3 (Such as NH3 combustion). So, catalytic combustion of NH3 is supposed to be a promising method to solve this problem but there is a rare report on that. The NOx emissions or N-2 selectivity performances in the NH3 oxidation process with different catalyst was conducted with Density functional theory (DFT) and experimental studies. Results showed that, when Fe2O3 was used as catalyst, the conversion efficiency of NH3 was 96.2%, and the selectivity of N-2 was 97.7%, which was higher than oxidation of NH3 without catalyst. DFT simulation showed that NH3 and O-2 can be separately adsorbed on Fe (top) of Fe2O3 (001), the adsorption of NH3 and O-2 were enhanced when they were put on Fe (top) of Fe2O3 (001) at the same time. Meanwhile, the length of inter-atomic bond increased thus creating oxygen vacancy, which promoted the oxidation of NH3. Finally, a Ni modified Fe-based catalyst (NiO10%/Fe2O3 30%/Al(2)O(3)60%), full of oxygen vacancy (confirmed with X-ray photoelectron spectroscopy (XPS)), was fabricated with impregnation method. The adsorption of NH3 and O-2 were further enhanced (confirmed by DFT simulation), the NH3 conversion efficiency and the N-2 selectivity were stably improved to 96.8% and 100%. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

关键词： Catalytic combustion of NH3 Ni-modified Fe-based catalyst, oxygen vacancy

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A novel relation for heat flow using Maxwell thermoelectricity analogy

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INTERNATIONAL COMMUNICATIONS IN heat AND MASS transfer 2020年 117卷 104745-104745页

作者： Liu, Yi Li, Ling Wang, Jianli 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 Southeast Univ Dept Mech Engn Jiangsu Key Lab Design & Manufacture Micronano Bi Nanjing 210096 Peoples R China

In this paper, the reliability of thermoelectric analogy under transient conditions is discussed. By comparing the similarity between the expression of the transient electricity and the expression of the non-Fourier heat transfer heat flow, it is believed that the thermoelectric analogy is still valid. And according to Maxwell's equations, an unknown field, which is similarly to the magnetic field, will generated in the vertical direction of the heat flux, and a thermal Maxwell's equation is present. In addition, according to the thermoelectric analogy, the heat flux equation satisfying the Lorentz transformation has been directly given, which is a more complicated differential-integral equation and can be used to describe some non-Fourier phenomena.

关键词： Non-Fourier heat conduction Thermoelectricity analogy

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Study of the Technologies for Freeze Protection of Cooling Towers in the Solar System

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ENERGIES 2022年第24期15卷 9640-9640页

作者： Liu, Jingnan Zhang, Lixin Chen, Yongbao Yin, Zheng Shen, Yan Sun, Yuedong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Sch Mech Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China China Gen Machinery Ind Assoc Cooling Equipment Branch Beijing 100097 Peoples R China Shanghai Tongchi Heat Exchanger Sci Tech Co Ltd Shanghai 200433 Peoples R China

A cooling tower is an important guarantee for the proper operation of a solar system. To ensure proper operation of the system and to maintain high-efficiency points, the cooling tower must operate year-round. However, freezing is a common problem that degrades the performance of cooling towers in winter. For example, the air inlet forms hanging ice, which clogs the air path, and the coil in closed cooling towers freezes and cracks, leading to water leakage in the internal circulation. This has become an intractable problem that affects the safety and performance of cooling systems in winter. To address this problem, three methods of freeze protection for cooling towers are studied: (a) the dry and wet mixing operation method-the method of selecting heat exchangers under dry operation at different environments and inlet water temperatures is presented. The numerical experiment shows that the dry and wet mixing operation method can effectively avoid ice hanging on the air inlet. (b) The engineering plastic capillary mats method-its freeze protection characteristics, thermal performance, and economics are studied, and the experiment result is that polyethylene (PE) can meet the demands of freeze protection. (c) The antifreeze fluid method-the cooling capacity of the closed cooling towers with different concentrations of glycol antifreeze fluid is numerically studied by analyzing the heat transfer coefficient ratio, the air volume ratio, the heat dissipation ratio, and the flow rate ratio. The addition of glycol will reduce the cooling capacity of the closed cooling tower.

关键词： solar system cooling tower dry and wet mixing operation engineering plastic freeze protection

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Finite element analysis of heat transfer performance of vacuum glazing with low-emittance coatings by using ANSYS

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ENERGY AND BUILDINGS 2020年 206卷 109584-000页

作者： Zhu, Qundong Wu, Weidong Yang, Yingying Han, Zhiming Bao, Yiwang Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jun Gong Rd Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China China Bldg Mat Acad 1 Guan Zhuang Dong Li Beijing Peoples R China

As a new transparent insulation material, vacuum glazing with Low-E (low emittance) coating has drawn more and more attentions thanks to its excellent performances: outstanding thermal and sound insulations, anti-frosting, resisting wind press capacity, and good durability. However, a comprehensive analysis and evaluation on the heat transfer performance of Low-E vacuum glazing are still missing in the current literatures. In this work, the influences of various aspects on the heat transfer performance of Low-E vacuum glazing were analyzed based on the Finite Element Analysis (FEA) method, including thickness of substrate glass, width of the sealing edge, materials and spacing of support pillar array, and insulation frame structure. The simulated results show the following, 1) with the increase of the thickness of the substrate glass, the heat transfer coefficient of the Low-E vacuum glazing rises slowly in a linear trend. The larger the size of the whole piece of the glazing, the more slowly it rises;2) the Low-E vacuum glazing heat transfer coefficient declines linearly with the decrease of the width of the sealing edge;3) as the support pillar array spacing increases and the thermal conductivity of the support pillar array decreases, the Low-E vacuum glazing heat transfer coefficient decreases;4) the use of thermal insulation frame structure can improve the insulation efficiency of the vacuum glazing. Experiments were carried out on a Low-E vacuum glazing, and the heat transfer coefficient of this vacuum glazing was determined by the Building heat Resistance-Ill (BHR-III), an equipment for insulation performance testing. The simulated result matches well with the experimental result, with a relative deviation of 2.8%, which confirms the reliability of the simulation result. This work is expected to provide guidance for optimization design of Low-E vacuum glazing and its insulation performance evaluation. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Low-E vacuum glazing Thermal insulation heat transfer performance Finite element

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PREPARATION AND SIMULATION OF THE ON-LINE SiO2/S COATING FOR COKING INHIBITION IN THE INDUSTRIAL CRACKING FURNACE

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BRAZILIAN JOURNAL OF CHEMICAL engineering 2019年第4期36卷 1571-1586页

作者： Wang, Zhiyuan Ding, Xudong Huo, Guanping Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

Coke formation inside radiant coils is one of the main problems during thermal cracking of hydrocarbons. The on-line preparation of the coating for coking inhibition is a promising technology because it provides more flexibility to the operators on site. The SiO2/S coating was prepared on the inner surface of coils in an 8-year-served GK-VI industrial cracking furnace. The effects of the coating preparation process on the operation of TLE were studied. The coking rates of the tube with and without coating preparation were evaluated by the trend change of tube metal temperature. Simulations of the coating deposition process were further carried out using the computational fluid dynamics approach. The results showed that a significant temperature increase at the outlets of TLEs during coating preparation were due to the accumulation of SiO2 and S in a loose form under the TLE operating conditions when the concentration of coating precursors was 7500 ppm (wt. %). In the three tests, coating precursors were mainly completely consumed in tubes and TLEs. For the coated tube, the run time was extended by 4-7 days because the catalytic coking was decreased. No significant changes in the distribution of products and molar yields of main products were observed. In the simulations, it was found that increasing the inlet flow rate led to a more uniform thickness and improved the mass content of sulfur in the coating. In the tube bend section, circumferential nonuniformities for the deposition were due to circumferential differences in the temperatures and mass fractions. The mass fraction of S in the coating was within the range of 0.02%-0.1%. The control step for the SiO2/S coating deposition was kinetic. Based on the simulation results, the optimized coating preparation parameters were determined, i.e., the inlet flow rate of 15t/h, the outlet temperature of 1093K and the inlet mass concentration of 3000 ppm (wt. %).

关键词： Industrial cracking furnace On-line SiO2/S coating Coke formation CFD Coating deposition

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Study on the heat and mass transfer characteristics of wet air in metal foam in the space station environment

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Applied Thermal engineering 2025年 277卷

作者： Guowei Zhu Liang Zhang Yujuan Xia Hantao Zhou School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China China National Institute of Standardization Beijing 100191 China

This paper has developed a novel dehumidification device for space station environment, which uses foam copper as the core, with a Stirling refrigerator providing cooling, heat pipes assisting in heat conduction and a siphon water guidance system employed to remove condensate. Experiments on dehumidifying wet air within the foam copper were then carried out under simulated microgravity dehumidification conditions. The experimental conditions included different inlet air temperatures, humidities, air velocities, and cold end temperatures of the Stirling refrigerator. The experimental research indicates that as the inlet air temperature rises from 20 °C to 30 °C, the mass transfer coefficient increases by 57.06 %, and the sensible heat coefficient rises by 10.62 %. When the air velocity increases from 0.4 m·s −1 to 1.4 m·s −1 , these two coefficients increase by 111.79 % and 170.83 %, respectively. In contrast, increasing the relative humidity from 50 % to 80 % results in a 34.09 % decrease in the sensible heat coefficient, while the mass transfer coefficient increases by 11.4 %. When the cold-end temperature rises from 8 °C to 13 °C, the sensible heat transfer and mass transfer coefficients increase by 9.63 % and 4.06 %, respectively. Based on this, a sensitivity analysis was conducted using the experimental data, and heat and mass transfer correlations were fitted. The mean standard deviations of the heat and mass transfer correlations are 3.74 % and 6.30 %, respectively, indicating a high degree of fitting accuracy. This work provides a new humidity control solution for future space station thermal management systems.

关键词： heat and mass transfer Metal foam Space station environment Wet air

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