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SSRN 2022年

作者： Zhong, Shao-Geng Ren, Yan Wu, Weidong Yang, Ying-Ying Yang, Qi-Guo 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

A mathematic-physical model was established to explore the local heat transfer characteristics of supercritical CO2 in semicircular and circular channels under cooling condition, which was applied in the field of supercritical CO2 Brayton cycle. The numerical method was validated by the experimental data with the average error of 3.79%, meeting the accuracy requirement. And the operation pressure, cooling heat flux, inlet velocity and hydraulic diameter were 8~9 MPa, 10~14 kW·m-2, 1.2~5 m·s-1 and 1~2 mm, respectively. The results showed that the local heat transfer coefficient of supercritical CO2 would increase at first and then decrease along the flow direction regardless of the semicircular channel and circular channel, and the peak value gradually decreased with increasing operation pressure and disappeared when the inlet velocity exceeded 3 m·s-1. Meanwhile, the heat transfer performance of the semicircular channel was weaker than that of the circular channel due to the influence of the corner area and the buoyant effect, and the latter played a dominant role. For the horizontal flow, the buoyant effect was increased, while the heat transfer was decreased with increasing hydraulic diameter of the semicircular channel. Besides, the influence of different flow directions on the heat transfer performance of the semicircular channel (about 6.2%) was greater than that of the circular channel (about 0.48%, and could be ignored). Finally, the heat transfer correlation of the supercritical CO2 cooling process in the horizontal semicircular channel was modified by considering the influence of the dimensionless buoyancy effect and hydraulic diameter, and the prediction errors of 90% correlation calculation results were within ±14% after the modification. These results will provide some theoretical guidance on the design and optimization of the cooler for the supercritical CO2 Brayton cycle system. © 2022, The Authors. All rights reserved.

关键词： heat flux

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An Investigation on the Formation and flow Characteristics of Nature Gas Hydrates at Different Loop Inclination Angles

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SSRN 2022年

作者： Liu, Ni Wang, Cheng Meng, Fei Yang, Liang Liu, Daoping School of Energy and Power Engineering The University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

One of the major issues in flow assurance includes pipeline plugging due to gas hydrate formation and deposition,which makes it imperative to look for appropriate hydrate control strategies. In this study, a high-pressure visual flow loop was used to analyze the influence of different inclination angles (0°–4°) on the formation, flow, morphology evolution, deposition process, and mechanism of hydrates. The macro-parametric data, including pressure, temperature, velocity, hydrate induction time and hydrate volume fraction, were compared and analyzed. Results showed that the hydration reaction rate of downslope section is slightly faster than that of upslope section in inclined section. Although the amount of hydrate finally formed is the same, the hydrate in the downslope section is more dense. While the loop inclination angle had little effect on the amount of hydrate formation, with the increase of inclination angle, the induction time tends to decrease and the hydration reaction time will be longer overall. At 1° inclination angle, the induction time was the shortest and the hydration reaction time was the longest. The deposition process of the horizontal pipe is divided into four stages, in which large hydrate particles in the liquid phase are evenly distributed throughout the pipeline, forming a hydrate moving bed. The hydrate deposition process of the inclined pipe is also divided into four stages. Among them, the large hydrate particles in the liquid phase are concentrated on the upper wall of the pipeline, which causes the density of the upper part of the pipeline to be much higher than that of the lower part, forming a hydrate-fixed *** results of this study can deliver theoretical support to ensure the safe transportation of gas hydrate slurries. © 2022, The Authors. All rights reserved.

关键词： Gas hydrates

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Research on Bionic Airfoil Design Method Based on Re-Evolution Optimization and Multi Objective Application on Horizontal Axis Wind Turbines

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SSRN 2023年

作者： Huang, Shengxian Yan, Hua Qiu, Huihe 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 Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong

The design of specific airfoil for wind turbine is a crucial factor in the research of wind turbine performance and stability. Based on biomimetic methods and numerical optimization methods, a brand new airfoil design method is proposed without relying on any traditional airfoil and airfoil design experience. A new airfoil is successful designed that gives consideration to both aerodynamic performance and roughness sensitivity. Based on the actual engineering environment of a horizontal axis wind turbine, the multi-island genetic algorithm is used to adjust the profile of the biomimetic airfoil (Dol-Rot24°). The optimized airfoil is named as Dol-Opt. In the performance verification of the Dol-Opt airfoil, it is found that compared with the Dol-Rot24°, the lift coefficient of the Dol-Opt airfoil is increased by 171.06%, and the lift-to-drag ratio is increased by 52.41% at most. Moreover, the roughness sensitivity of the Dol-Opt is also the optimum among the three airfoils (S809, Dol-Rot 24°, Dol-Opt). By conducting numerical simulations, it is found that the newly optimized wind turbine blades exhibit greatly improved energy efficiency. The purpose of this study is to provide effective references for the design, bionic methods, and practical engineering applications of wind turbine specific airfoils. © 2023, The Authors. All rights reserved.

关键词： Airfoils

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Research on Bionic Airfoil Design Method Based on Re-Evolution Optimization and Multi Objective Application on Horizontal Axis Wind Turbines

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SSRN 2023年

作者： Huang, ShengXian Yan, Hua Qiu, HuiHe 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 Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong

The design of specific airfoil for wind turbine is a crucial factor in the research of wind turbine performance and stability. Based on bionic methods and numerical optimization methods, a brand new airfoil design method is proposed without relying on any traditional airfoil and airfoil design experience. This study proposes a re-evolution method (numerical optimization methods) suitable for designing bionic airfoils based on the previously proposed bionic airfoil (Dol-Rot24°), which was inspired by the Dall's Porpoise. According to this method, a new airfoil is successful designed that gives consideration to both aerodynamic performance and roughness sensitivity. The research content mainly focuses on two aspects: new airfoil design and the new airfoil performance verification. In terms of the new airfoil design, a surrogate model based on radial basic function (RBF) is established for predicting aerodynamic performance and roughness sensitivity of airfoils. This surrogate model can significantly reduce the cost of bionic airfoil optimization calculations, and control the time of 8000 optimization iterations within 1 minute. Based on the actual engineering environment of a horizontal axis wind turbine, the multi-island genetic algorithm is used to adjust the profile of the Dol-Rot 24° airfoil. The optimized airfoil is named Dol-Rot 24° opt. In the performance verification of the Dol Rot 24° opt airfoil, it is found that compared with the Dol Rot 24° airfoil, the lift coefficient of the Dol Rot 24° opt airfoil is increased by 171.06%, and the lift-to-drag ratio is increased by 52.41% at most. Moreover, the roughness sensitivity of the Dol-Rot 24° opt airfoil is also the best among the three airfoils (S809, Dol-Rot 24°, Dol-Rot 24° opt). By modeling the three airfoils according to the NREL Phase VI wind turbine blade parameters and conducting numerical simulations, it is found that the newly optimized wind turbine blades exhibit greatly improved energy efficiency. Th

关键词： Airfoils

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Research on Bionic Airfoil Design Method Based on Re-Evolution Optimization and Multi Objective Application on Horizontal Axis Wind Turbines

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SSRN 2023年

作者： Wang, Ying Huang, ShengXian Yan, Hua Qiu, HuiHe 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 Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong

关键词： Airfoils

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Prediction of oil production based on multivariate analysis and self-attention mechanism integrated with long short-term memory

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PETROLEUM SCIENCE AND TECHNOLOGY 2024年

作者： Yan, Hua Liu, Ming Yang, Bin Yang, Yang Ni, Hu Wang, Haoyu Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Shengli Oilfield Co Petr Engn Technol Res Inst SINOPEC Dongying Peoples R China

The accurate oil prediction of wells is essential for making informed decisions regarding the extension of the well lifespan and the enhancement of oil recovery rates. However, the prediction of oil well production is highly challenging due to the complex, nonlinear, and non-stationary data influenced by reservoir geological characteristics and operational adjustments. To address this, a novel prediction method for oil well production is proposed in this study. Firstly, the data-cleaning approach designed in this study is utilized to eliminate outliers from the raw dataset and impute missing values. Subsequently, relevant features are identified through analysis to form a usable dataset. The proposed deep learning neural network, namely the self-attention mechanism integrated with long short-term memory, is trained and learned on this dataset. Finally, the predictive performance of the model is validated using a set of actual oil production data. Through data experiments, the proposed model effectively predicts oil well production with superior accuracy compared to baseline models, achieving an R-squared of 0.872. This method provides reliable decision support for optimizing oil field development and management.

关键词： Data cleaning deep learning neural network long short-term memory oil prediction self-attention

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Impact of gas impurities on the Hg⁰ oxidation on high iron and calcium coal ash for chemical looping combustion

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ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 2021年第34期28卷 46130-46146页

作者： Liu, Zhuang Liu, Dunyu Jin, Jing Feng, Liang Ni, Mingguo Zhao, Bingtao Wu, Xiaojiang Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China Shanghai Boiler Works Co Ltd R&D Div Shanghai 200245 Peoples R China

Coal-based mercury pollution from power plants has received increasing attention. In a previous study, high iron and calcium coal ash (HICCA) was found as a promising oxygen carrier (OC) for chemical looping combustion (CLC). The purpose of this study was to investigate the catalytic effect of HICCA on Hg-0 removal as well as the impacts of several gas impurities, such as HCl, SO2, and NO. Experiments on Hg-0 removal efficiencies for different atmospheres were performed in the fixed-bed reactor at 850 degrees C. Based upon the characterization of BET, SEM, XRD, XPS, and EDS of reaction products, the reaction mechanisms of different gases with the HICCA samples were established. The mechanisms were further explained using the thermodynamic equilibrium calculations. The experimental results showed that the Hg-0 removal efficiency using HICCA was 11.60%, while the corresponding value in the presence of 50 ppm HCl was 90.46%. Hg-0 removal by HICCA involving HCl is mainly attributed to homogeneous reaction between Hg-0 and HCl as well as the formation of reactive species (Cl, Cl-2, Cl2O, O, S, and SCl2) through the reactions of HCl with Fe2O3 and CaSO4 in HICCA. The formation of C-Cl bond is not the main pathway for the promotional effect of HCl on Hg-0 removal. SO2 played a negative role in Hg-0 removal by HICCA. The inhibition of SO2 may be attributed to its effect on the reduction of Fe2O3 and its bonding with C-O, COOH, and C(O)-O-C. NO enhanced Hg-0 removal by HICCA primarily through the homogeneous reactions of Hg-0 with N2O and O. In addition, NO also interacted with HICCA and promoted the heterogeneous oxidation of Hg-0 by producing more C-O, C=O, and COOH/C(O)-O-C on HICCA surface. This study proved the effectiveness of HICCA on Hg-0 removal in iG-CLC and revealed the mechanisms of the interaction between HCl/SO2/NO and MxOy/CaSO4 as well as carbon-oxygen groups.

关键词： Mercury removal Coal ash Gas impurities Chemical looping combustion

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Effect of dispersant on the performances of an ice slurry-wet precooling system

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CASE STUDIES IN THERMAL engineering 2023年 52卷

作者： Yang, Yingying Yang, Qingyu Wu, Weidong Ren, Xueming Ren, Yan 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 516 Jungong Rd Shanghai 200093 Peoples R China

This study addresses the problem of prolonged precooling time and excessive weight loss of fruits and vegetables during postharvest processes. Ice slurry precooling system shows potential but faces challenges like low undercooling and ice blockage. Dispersants are introduced to optimize heat and moisture transfer as well as the flow characteristics of the ice slurry. This research investigates the effects of four dispersants on the performance of an ice slurry-based wet precooling system through experiments. key parameters analyzed include temperature and humidity in the chamber, cooling rate, and weight loss rate of the tested load. Results show that the addition of dispersants effectively reduces the freezing temperature, enhancing the cooling rate in the system. Among the four dispersants tested, sodium diacetate yields the lowest freezing temperature of -6.4 degrees C and the highest cooling rate of 0.3 degrees C min-1. Furthermore, dispersants influence moisture transfer between ice slurry and circulating air, impacting the humidity within the precooling chamber. Notably, the addition of sodium diacetate results in the lowest weight loss rate of 2.74 %. This research shows the potential of using dispersants in ice slurry-based wet precooling systems to enhance the postharvest preservation of fruits and vegetables.

关键词： Postharvest preservation Wet precooling system Ice slurry Dispersant

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A novel hybrid forecasting approach for NOx emission of coal-fired boiler combined with CEEMDAN and self-attention improved by LSTM

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ASIA-PACIFIC JOURNAL OF CHEMICAL engineering 2024年第4期19卷 e3057-e3057页

作者： Yan, Hua Chen, Yunchi Yang, Bin Yang, Yang Ni, Hu Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China China Resources Power Wenzhou Co Ltd Wenzhou Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China

The precise prediction of NOx generation concentration in coal-fired boilers serves as the foundational cornerstone for the judicious optimization and control of selective catalytic reduction denitrification (SCR) systems. Owing to the intricate nature of the denitrification process within SCR, there exists a temporal delay in regulating the ammonia injection rate based on the monitored data of NOx concentration at the SCR inlet. Such delays can give rise to ammonia leakage and subsequent obstruction of the air preheater. In light of this, a predictive model, CEEMDAN-LSTM-SA, is proposed as an amalgamation of data decomposition and the LSTM (long short-term memory) fusion self-attention mechanism within a deep learning network, which is introduced to forecast the NOx emission concentration at the SCR inlet of coal-fired units. To mitigate the impact of data outliers on the training effectiveness of the model, a clustering method coupled with a statistical testing strategy is initially applied to refine the dataset first. CEEMDAN data decomposition technology is leveraged to facilitate the breakdown of data, alleviating its non-stationary and intricate characteristics. Subsequently, through spectral analysis, the decomposed components are grouped and aggregated to form novel data elements, which are then subjected to prediction by the constructed LSTM-SA deep learning network. The ultimate NOx emission concentration prediction value is derived through a process of fusion. Upon scrutinizing and comparing the predictions derived from various models using coal-fired power plant data, it is evident that the performance metrics of CEEMDAN-LSTM-SA predictions exhibit a mean absolute error of 7.425, mean absolute percentage error of 2.415%, root mean square error of 9.715, R-squared (R2) value of .789, mean absolute relative error of 2.109%, and a Theil's information criterion of .016. In contrast to other models, including traditional self-attention networks, LSTM, and LST

关键词： CEEMDAN data cleaning LSTM NOx emission self-attention mechanism

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Numerical study of heat transfer characteristics of phase change materials reinforced with porous media based on hybrid mesh

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SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS 2024年 65卷

作者： Wang, Zilong Zhu, Liucan Zhang, Hua Yu, Guoxin Li, Jing Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Qingdao Haier Smart Technol R&D Co Ltd 1 Haier Rd Qingdao Shandong Peoples R China

To address the drawbacks of inadequate energy density as well as utilization effectiveness in solar energy utilization, phase change energy storage offers a possible option. However, the low thermal conductivity of traditional phase change materials (PCMs) restricts the extent to which solar energy utilization can be enhanced. In this paper, the impact of the metal foam (MF) on the solid-liquid interface, the flow field, the enhancement heat transfer mechanism during the paraffin wax (PX) melting process and thermal storage characteristics was analyzed. Besides, a three-dimensional mathematical model of MF-PX using the hybrid mesh technique was established and software ANSYS-FLUENT was used for simulation. The results indicated that, the hybrid mesh exhibited a reduction of 52.75 % in mesh count compared to the unstructured mesh, resulting in 45 % reduction in computational time. Moreover, the hybrid mesh also showcased improved mesh quality that the unstructured mesh was mainly distributed in the range of 0.48-0.6, while within the range of 0.84-1.0 for the hybrid mesh. More important, the maximum relative error between experimental and simulation was 8.67 %, indicating that the model can make a reasonable prediction. With the proportions of MF increased from 0.11 % to 0.43 %, both the Rayleigh number (Ra) and its amplification decreased. At 800 s, the Ra decreased from 1.76E+07 to 1.20E+07, while the amplification of the Ra was reduced from 1.88E+07 to 1.30E+07. In addition, the natural convection proportions of CMF decreased from 96.31 % to 80.65 %. These observations indicated that natural convection was the primary heat transfer mechanism, and the conduction was enhanced by the increasing proportion of MF. Finally, in terms of heat storage characteristics, the heat storage capacity and heat storage rate of the composite PCM slightly decreased. The heat storage values decreased from 19.30 kJ to 18.66 kJ. Similarly, the heat storage rates decreased from 19.86 J/s

关键词： Phase change materials Numerical simulation Copper metal foam Hybrid mesh heat transfer enhancement

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