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Lattice Boltzmann Simulation of Cavitating flow in a Two-Dimensional Nozzle with Moving Needle Valve

PROCESSES 2024年第4期12卷 813页

作者： Yang, Fan Dai, Mengyao Jin, Hu 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

A cascaded pseudo-potential lattice Boltzmann model and refilling algorithms for moving boundary treatment were used to simulate the large density ratio cavitating flow in a two-dimensional nozzle with the periodic motion of the needle valve. The relationships between density variation at the cavitation zone, the evolution of force acting on the lower boundary of the sack wall region, and the surface of the needle valve with time under different needle valve motion frequencies were obtained. The results indicate that the inception and evolution of cavitation mainly exist in the vicinity of the lower boundary of the sack wall region. The density at cavitation decreases by approximately three orders of magnitude, while the force on the lower boundary of the sack wall region decreases by about one order of magnitude. Since cavitation does not exist in the vicinity of the needle valve, the forces are mainly influenced by the periodic motion of the needle valve and do not change significantly. Changes in the frequency of needle valve motion affect the time taken for cavitation evolution to reach a relatively steady state but do not significantly affect the forces acting on the different components.

关键词： lattice Boltzmann method cavitating flow pseudo-potential model moving boundary refilling algorithms

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A novel hybrid approach for high-efficiency and low-load airfoil design for H-type vertical axis wind turbines

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PHYSICS OF FLUIDS 2025年第3期37卷

作者： Huang, ShengXian Ng, Eddie Yin Kwee Li, Chun Zhang, Yongxing Moghtaderi, Behdad Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Nanyang Technol Univ NTU Sch Mech & Aerosp Engn Singapore 63904455 Singapore Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China China Univ Petr Natl Engn Lab Pipeline Safety MOE Key Lab Petr Engn Beijing Key Lab Urban Oil & Gas Distribut Technol Beijing 102249 Peoples R China Univ Newcastle Ctr Innovat Energy Technol Callaghan NSW 2308 Australia

The bionic approach enables the rapid excellent design, avoiding the complexity and time-consuming traditional optimization processes. To swiftly develop a high-efficiency airfoil suitable for vertical axis wind turbines (VAWTs), this study designs a novel dolphin-average airfoil (Dol-Ave airfoil) inspired by the streamlined profile of the Dall's porpoise's head. Furthermore, considering the challenges in aligning biologically inspired designs with practical engineering requirements, the Archive-based Micro Genetic Algorithm (AMGA) is adopted to refine the Dol-Ave airfoil contours by targeting high energy capture efficiency and low load. The combination of bio-inspired method and numerical optimization is referred to as the hybrid optimization method. The results of numerical simulations and comparative verification show the following: (1) When tip-speed ratio(TSR) is 0.5, compared to National Advisory Committee for Aeronautics (NACA) 0018 airfoil, the power coefficient of the Dol-Ave airfoil increases by 52.66%. However, under the high tip-speed ratio conditions, no improvement in wind energy utilization is observed. (2) The optimized airfoil (Dol-Ave opt) achieves power coefficient optimization across the full tip-speed ratio range. Compared to NACA 0018, when TSR = 0.5, the power coefficient of the Dol-Ave opt airfoil increases by 30.01%;when TSR = 1.2, the increase is 8.16%. (3) Both the Dol-Ave airfoil and the Dol-Ave opt airfoil show improvements in lateral thrust load. The bio-inspired airfoil design method and the hybrid design approach proposed in this study offer valuable insights for airfoil design.

关键词： Vertical axis wind turbine

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Theoretical model of microlayer and macrolayer evaporation considering heating surface temperature radial distribution at the bottom of the bubble

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INTERNATIONAL COMMUNICATIONS IN heat AND MASS transfer 2023年 140卷

作者： Gao, Ming Dong, Wu-han Shen, Zhong-Xiang Zhang, Li-xin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Based on the dynamic microlayer and macrolayer evaporation models, the mechanisms of single bubble micro and macrolayer evaporation were studied. The nucleate boiling heat transfer and the dynamic characteristics of a single bubble in micro and macrolayers are closely related to the wall temperature. The present work investigates the effects of time and distance on the formation of micro and macrolayer during the growth of a single bubble on a heated horizontal wall. A new complex microlayer and macrolayer model is established. The initial microlayer thickness, dry spot radius, and macrolayer thickness are calculated. The model is compared with experimental data on the evaporation of water and ethanol in the presence of nucleating bubbles. It is found that the previous experimental data are within the range of +/- 25% of the proposed model, and the predicted data of the model are in good agreement with the experimental data.

关键词： Microlayer Macrolayer Initial microlayer thickness Wall temperature Theoretical model

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Effects of hydrophilic surface on heat transfer performance of spray cooling

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2024年 201卷

作者： Wang, Juping Liu, Ni Wang, Yan Wang, Meiting Zhang, Hua 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

The heat transfer characteristics of two hydrophilic surfaces, SM-QS3100 and ZCP-0010, were investigated in single-phase and two-phase zones in comparison to a smooth surface concerning spray cooling. The results showed that in the single-phase zone, the SM-QS3100 and ZCP-0010 hydrophilic surfaces could not enhance heat transfer, and the ZCP-0010 surface with better hydrophilicity had the worst heat transfer characteristic. Compared with the smooth surface, the heat transfer coefficients of the two surfaces decreased by 11.5% and 28.8% at a heat flux of 58.0 W/cm2. Within the two-phase zone, both surfaces positively influenced heat transfer, with the ZCP-0010 surface, being more hydrophilic, exhibiting a more notable enhancing effect. The heat transfer coefficients exhibited 12% and 11.5% increments at a heat flux of 151.7 W/cm2. However, the contribution of hydrophilic surfaces to heat transfer tended to be consistent with the heat flux increasing. Although the temperature homogeneity of each surface became worse, the temperature uniformity on the hydrophilic surfaces was better in both the single-phase and two-phase zones.

关键词： Spray cooling Hydrophilic surface Temperature uniformity Single-phase zone Two-phase zone

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heat pump drying kinetics modeling and prediction for Lentinus edodes based on orthogonal experimental

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CASE STUDIES IN THERMAL engineering 2024年 63卷

作者： Hou, Yaxiang Wu, Weidong Wang, Jing Yang, Yingying Zhang, Hua 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

To accurately understand the moisture variation and drying characteristics of Lentinus edodes (L. edodes) during the drying process, the kinetics model of L. edodes with a wider application range was investigated. First, the heat pump drying kinetics model for L. edodes was fitted, verified and extended based on the orthogonal experimental data. Then, the expression of moisture ratio of L. edodes with respect to drying time, air supply temperature (AST), loading density (LD) and circulating air volume (CAV) was proposed, and interaction effects of the three key parameters on the drying time were studied based on the prediction model. The findings indicated a substantial agreement between the predicted and experimental values. The drying time could be shortened by increasing the air supply temperature and the circulating air volume or decreasing the loading density. Among these three factors, the AST had the greatest impact on drying time, followed by CAV and LD. For every 48 g/m2 reduction in LD and 11.3 m3/h increase in CAV, the drying time could be reduced by 10.5-29.9 min. Similarly, increasing the AST by 1 degrees C and the CAV by 11.3 m3/h could decrease the drying time by 13.7-100.6 min. The research results are helpful to optimize the drying process, improve the drying efficiency, and provide guidance and references for practical production of L. edodes HPD.

关键词： Air supply temperature Circulating air volume heat pump drying Kinetics model Lentinus edodes Loading density Nomenclature

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The distorted power of medical surgical masks for changing the human thermal psychology of indoor personnel in summer

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INDOOR AIR 2021年第5期31卷 1645-1656页

作者： Zhang, Ruhang Liu, Jianhua Zhang, Liang Lin, Jindi Wu, Qingqing Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

The medical surgical mask (MSM) has been the essential protective equipment in people's daily work. The experimental purpose is to explore the effects of wearing MSM on human thermal sensation, thermal comfort, and breathing comfort in office buildings in summer. A total of 30 healthy college students were recruited for the testing. The experiment was carried out in a climate chamber, which can simulate the office buildings in summer. The experiment collects the subjects' skin temperature, microclimate in the mask, and subjective votes, including thermal sensory votes (TSV), thermal comfort votes (TCV), and respiratory comfort votes (BCV). Experimental results show that wearing MSM has no significant effect on the skin temperature of the human body. The microclimate temperature inside the MSM reaches over 34celcius, and the relative humidity reaches over 70%. The high-temperature and high-humidity microclimate put human beings in an uneven thermal environment, which leads to poor human tolerance to the thermal environment and becomes the main reason for destroying human thermal comfort. Wearing MSM has a significant impact on the subjective thermal sensation, thermal comfort, and breathing comfort of the human body, and the impact becomes more significant as the environmental temperature increases. Once the mask is taken off, the human body will enter an extremely comfortable environment, resulting in an excessively high vote value. The difference in voting values before and after removing the mask becomes larger with the environmental temperature. By fitting the voting results and perform data processing, it can be found that wearing MSM will reduce the neutral temperature by 1.5 degrees C, and the environmental temperature with the optimal thermal comfort by 1.4 degrees C, and as the temperature increases, the respiratory discomfort will become more and more intense. Regardless of whether wearing a MSM, the subjects preferred a slight warmer environment. In conclu

关键词： breathing comfort environmental temperature medical surgical masks thermal comfort thermal sensation

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Performance analysis and thermal comfort evaluation of a CO2 transcritical air-conditioning system for cabin thermal management of electric vehicles

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JOURNAL OF CLEANER PRODUCTION 2024年 479卷

作者： Jiang, Ziqi Li, Mengjia Liu, Zhixiang Tian, Yafen Li, Kang Liu, Ni Zhang, Hua 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 investigates the effects of different operating conditions on system performance and optimal discharge pressure by establishing a numerical model of CO2 cabin thermal management system and validating the model with experimental data. Besides, two different optimal discharge pressure formulas are attained based on different parameters. It is found that the multi-parameter formula is more accurate than the other with a maximum deviation of 2.64%. Then, the control strategy is designed based on this formula to investigate the coupled effects of thermal comfort and economical performance under different driving patterns and different ambient temperatures. The elevation of PMV indicator can weaken the declining rate of power and energy consumption, enhance the driving range and reduce annual operation cost in cooling mode (AOCc) of vehicle. The boundary of thermal comfort zone (PMV = 0.5) exhibits excellent economical efficiency due to its higher growth rate of driving range (6.3%) and reduction rate of AOCc (7.9%) from 0 to 0.5 PMV at the ambient temperature of 35 degrees C. And this improvement is more prominent under higher ambient temperature.

关键词： Electric vehicle Optimal discharge pressure Driving range Economical analysis CO2 cabin thermal management system

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HELIYON 2024年第3期10卷 e25071页

作者： Yang, Jie Guo, Hao-han Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Based on the microscopic polycrystalline fatigue crack propagation (MPFCP) model, the MPFCP behaviours of GH4169 alloy under different micro-notch depths and lengths (constraints) were studied from aspects of MPFCP path, MPFCP rate and stress distribution. The influences of the initial crack angle on MPFCP behaviour were further explored. It was observed that the grain boundary, the grain size and the stress state were different during crack propagation under different constraints, resulting in different MPFCP paths. The MPFCP path was straighter under high constraints, and the MPFCP rate was related to the micro-notch size and the loading direction. The crack tip needed more stress accumulation at low constraints than under high constraints to ensure smooth MPFCP behaviour. The influence of the initial crack angle on the MPFCP path was mainly reflected in the grain interior where the initial crack was located. The initial crack angle had a greater influence on the MPFCP rate than on the MPFCP path.

关键词： Constraint Fatigue crack propagation Polycrystalline alloy Crystal plasticity Microscopic

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Investigation on mixed particle classification based on imaging processing with convolutional neural network

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POWDER TECHNOLOGY 2021年 391卷 267-274页

作者： Tian, Chang Cai, Yang Yang, Huinan Su, Mingxu 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

For the classification of mixed particle with imaging method, the traditional processing techniques tend to extract the particle features from binary images, where particles can be classified by combining feature design corresponding to the particle type and classifiers, such as BP neural network and Support Vector Machine (SVM). However, the accuracies of these methods would be seriously influenced by particle agglomeration and imprecise feature design. In the work, the convolutional neural network (CNN) was introduced to extract the particle features in the image, where the particle localizations were obtained by implementing the region proposal network (RPN). Meanwhile, the particle segmentation at pixel level was achieved by a developed classifier and a fully convolutional network. A series of experiments were performed to a flowing mixed particle system consisting of spherical, elongated and irregular particles, and it showed that both the average accuracy and recall rate of SVM method were up to 87% with artificial feature design, while they were increased to 97% and 93% with CNN, respectively. For the median diameter (Dn(50)) of irregular particles, the latter method can also reduce the analysis error by more than 11%. It revealed that some shortages like imprecise feature design in traditional methods can be covered, and an end-to-end classified system can be formed to provide a more effective way for online analysis of flowing mixed particles. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Measurement Imaging Particle classification Convolutional neural network SVM

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An inverse fault detection and diagnosis (IFDD) strategy for practical application on chiller product

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INTERNATIONAL JOURNAL OF REFRIGERATION 2022年 134卷 24-34页

作者： Lu, Hailong Cui, Xiaoyu Han, Hua Liu, Jiangyan Zhang, Yunqian [a]School of Energy and Power Engineering University of Shanghai for Science and Technology 516 Jungong Road Yangpu District Shanghai 200093 PR China [b]Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093 PR China [c]CQ Midea General Refrigeration Equipment Co. Ltd. 15 Qiangwei Road Nanan District Chongqing 401336 PR China [d]School of Energy and Power Engineering Chongqing University Chongqing PR China

Current research on chiller fault detection and diagnosis (FDD) is usually based on the multi-classification method for mixed multiple fault types. The establishment of a multi-classification FDD model requires obtaining extensive test data of normal operation and multiple common faults at different fault levels, so the cost-to benefit ratio will not be accepted. In addition, because of the information interference between different types of fault data, FDD model is hard to avoid over-fitting or under-fitting, and there may be an intolerable high false alarm rate existing in product application. Therefore, it is difficult to promote FDD in actual chiller product applications. This paper proposes an inverse fault detection and diagnosis (IFDD) strategy, which is based on the characteristics of the target fault (the fault to be concerned) to establish a two-classification fault diagnosis model. Compared with the multi-classification method, the amount of fault test data required by the two classification methods to realize fault diagnosis can be greatly reduced. With IFDD strategy, the detection and diagnosis are completed simultaneously, while fast calculation speed, high diagnosis accuracy rate and low false alarm rate are achieved. The core of the IFDD strategy is to concentrate resources to capture the characteristics of the target fault, and no longer classify other types of faults and normal operating conditions, so it can avoid the influence of information interference between multiple types of fault data in the fault diagnosis model. In order to verify the feasibility of this strategy, a 200 ton variable-speed screw chiller has been tested on the laboratory, and a database of normal operation, refrigerant leakage, refrigerant overcharge faults, and a new operating condition of insufficient cooling water flow is initially established. Based on the sensors configured by the chiller unit and using the exponentially weighted moving-average (EWMA) control chart for

关键词： Inverse FDD Strategy Practical application Chiller product EWMA

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