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Enhanced efficiency in Concentrated Parabolic Solar Collector(CPSC) with a porous absorber tube filled with metal nanoparticle suspension

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Green Energy & Environment 2018年第2期3卷 129-137页

作者： Mohammad Hatami Jiafeng Geng Dengwei Jing Mechanical Engineering Department Esfarayen University of Technology (EUT) International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University

In this study, effects of different nanoparticles and porosity of absorber tube on the performance of a Concentrating Parabolic Solar Collector(CPSC) were investigated. A section of porous-filled absorber tube was modeled as a semi-circular cavity under the solar radiation which is filled by nanofluids and the governing equations were solved by FlexPDE numerical software. The effect of four physical parameters, nanoparticles type, nanoparticles volume fraction(φ), Darcy number(Da) and Rayleigh number(Ra), on the Nusselt number(Nu) was discussed. It turns out that Cu nanoparticle is the most suitable one for such solar collectors, compared to the commonly used Fe_3O_4, Al_2O_3, TiO_*** the increased addition of Cu nanoparticles all the parameters φ, Da and Ra shows a significant increase against the Nu, indicates the enhanced heat transfer in such cases. As a result, low concentration of Cu nanoparticle suspension combined with porous matrix was supposed to be beneficial for the performance enhancement of concentrating parabolic solar collector.

关键词： Concentrating parabolic solar collector Porous absorber tube Nanofluid Nusselt number Finite Element Method

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Recent Advances in Machine Learning Research for Nanofluid-Based Heat Transfer in Renewable Energy System

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ENERGY & FUELS 2022年第13期36卷 6626-6658页

作者： Sharma, Prabhakar Said, Zafar Kumar, Anurag Nizetic, Sandro Pandey, Ashok Anh Tuan Hoang Huang, Zuohua Afzal, Asif Li, Changhe Anh Tuan Le Xuan Phuong Nguyen Viet Dung Tran Delhi Skill & Entrepreneurship Univ Sch Engn Sci Delhi 110089 India Univ Split FESB Split 21000 Croatia CSIR Indian Inst Toxicol Res Ctr Innovat & Translat Res Lucknow 226001 Uttar Pradesh India Univ Petr & Energy Studies Sustainabil Cluster Sch Engn Dehra Dun 248007 Uttarakhand India Ctr Energy & Environm Sustainabil Lucknow 226029 Uttar Pradesh India Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China PA Coll Engn Dept Mech Engn Mangaluru 574153 India Visvesvaraya Technol Univ Belgavi India Qingdao Univ Technol Sch Mech & Automot Engn Qingdao 266520 Peoples R China Hanoi Univ Sci & Technol Sch Mech Engn Hanoi 10999 Vietnam Ho Chi Minh City Univ Transport PATET Res Grp Ho Chi Minh City 717000 Vietnam HUTECH Univ Inst Engn Ho Chi Minh City 717000 Vietnam Univ Sharjah Dept Sustainable & Renewable Energy Engn Sharjah 27272 U Arab Emirates Natl Univ Sci & Technol NUST US Pakistan Ctr Adv Studies Energy USPCAS E Islamabad 44000 Pakistan

Nanofluids have gained significant popularity in the field of sustainable and renewable energy systems. The heat transfer capacity of the working fluid has a huge impact on the efficiency of the renewable energy system. The addition of a small amount of high thermal conductivity solid nanoparticles to a base fluid improves heat transfer. Even though a large amount of research data is available in the literature, some results are contradictory. Many influencing factors, as well as nonlinearity and refutations, make nanofluid research highly challenging and obstruct its potentially valuable uses. On the other hand, data-driven machine learning techniques would be very useful in nanofluid research for forecasting thermophysical features and heat transfer rate, identifying the most influential factors, and assessing the efficiencies of different renewable energy systems. The primary aim of this review study is to look at the features and applications of different machine learning techniques employed in the nanofluid-based renewable energy system, as well as to reveal new developments in machine learning research. A variety of modern machine learning algorithms for nanofluid-based heat transfer studies in renewable and sustainable energy systems are examined, along with their advantages and disadvantages. Artificial neural networks-based model prediction using contemporary commercial software is simple to develop and the most popular. The prognostic capacity may be further improved by combining a marine predator algorithm, genetic algorithm, swarm intelligence optimization, and other intelligent optimization approaches. In addition to the well-known neural networks and fuzzy- and gene-based machine learning techniques, newer ensemble machine learning techniques such as Boosted regression techniques, K-means, K-nearest neighbor (KNN), CatBoost, and XGBoost are gaining popularity due to their improved architectures and adaptabilities to diverse data types. The regularly us

关键词： Energy Fluids Layers Machine learning Nanoparticles

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Experimental study of bubble formation process on the micro-orifice in mini channels

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2020年 117卷 110144-110144页

作者： Zhang, Zhengzheng Li, Liangxing Xie, Wei Wang, Huasheng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Ning West Rd 28 Xian 710049 Peoples R China China Energy Engn Grp Planning & Engn CO LTD Ande Rd 65 Beijing 100120 Peoples R China

A visualized experimental system is designed and constructed to study the bubble behaviors on the micro-orifice in liquid layer. The test section is performed in a rectangular duct of 0.27 m x 0.006 m x 0.012 m, and the air is injected from an orifice with 0.49 mm in diameter. The gas flow rate is in the range of 0.3-60 ml/min, while the corresponding Reynolds number is ranged from 0.87 to 173.18. The effect of gas flow rate on bubble behaviors and bubble coalescence characteristics are investigated systematically. The results state that the bubble height, the radius of curvature at the apex and the bubble detachment volume show little variation with the gas flow rate when the gas flow rate is less than 24 ml/min. While the bubble contact line diameter increases firstly and then decreases. During the multi-bubble regimes stage, the detachment volume of both leading bubbles and trailing bubbles increase with the Weber number. The time interval between two adjacent bubbles or coalescence cycles is almost 0 when Weber number is above 18.27.

关键词： Bubble formation Coalescence characteristics Bubble volume Micro-orifice

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Performance investigation on a frost-free air source heat pump system employing liquid desiccant dehumidification and compressor-assisted regeneration based on exergy and exergoeconomic analysis

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ENERGY CONVERSION AND MANAGEMENT 2019年第Mar.期183卷 167-181页

作者： Su, Wei Li, Hang Sun, Bo Li, Shuhong Zhang, Xiaosong Southeast Univ Sch Energy & Environm Nanjing 210096 Jiangsu Peoples R China Xi An Jiao Tong Univ Inst Turbomachinery State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China Southeast Univ Minist Educ Key Lab Energy Thermal Convers & Control Nanjing 210096 Jiangsu Peoples R China Univ Illinois Energy Transport & Res Lab Dept Mech Sci & Engn Urbana IL 61801 USA

Frost build-up on the evaporator of air source heat pump severely deteriorates the heat transfer and subsequently reduces the performance of the system. Combining liquid desiccant dehumidification with heat pump system is an efficient strategy to achieve frost-free operation by dehumidifying the inlet air during winter in humid areas. In this paper, detailed energy, exergy and exergoeconomic analyses are performed for a frost-free air-conditioning system with integrated liquid desiccant dehumidification and compressor-assisted regeneration, in which the diluted liquid desiccant can be efficiently regenerated under low temperature condition. Parametric studies are conducted to appraise the influence of the important operation parameters on the performance of the proposed system. Then the hybrid system is optimized and compared from the exergoeconomic perspective. It is found that, the first and second largest exergy destructions take place in the regenerator and dehumidifier, which can be improved by increasing the investment costs. When the proposed system is optimized based on the exergoeconomics, the coefficient of performance and exergy efficiency increase by 13.02% and 12.73%, respectively. The total product unit costs can decrease by 12.64% compared to that under the basic operation condition.

关键词： Frost free heat pump system Compressor-assisted regeneration Exergoeconomic analysis Optimization

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Toward efficient photocatalytic pure water splitting for simultaneous H2 and H2O2 production

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NANO ENERGY 2019年 62卷 823-831页

作者： Xue, Fei Si, Yitao Wang, Miao Liu, Maochang Guo, Liejin Xi An Jiao Tong Univ Int Res Ctr Renewable Energy Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Suzhou Acad Suzhou 215123 Jiangsu Peoples R China

Although overall water splitting with particulate photocatalysts is considered as an ideal means towards solar-to-hydrogen conversion, practical application of the promising technique is greatly inhibited by the congenital defects including H-2/O-2 separation and unfavorable four-electron kinetics. In this context, photocatalytic overall water splitting for simultaneous H-2 and H2O2 generation via a two-electron pathway can readily address these issues. Here, we report a novel CoxNiyP cluster incorporated P-doped g-C3N4 photocatalyst (CoxNiyP-PCN) by a two-step phosphating method that presents such unique behavior for pure water splitting into stoichiometric H-2 and H2O2. The highest H-2 evolution rate reaches 239.3 mu mol h(-1) g(-1), achieved over the CoNiP-PCN photocatalyst, which is among the best reported activities for overall water splitting. It is found that both P and the cluster cocatalyst are critical to the remarkably improved photocatalytic activity. Specifically, P as a substitution of C in PCN introduces a positive charge center (P+), reinforcing the chemical connection between PCN and CoNiP, in a form of P+-P delta--Co delta+/Ni delta+. This unique bridging effect, together with the extended light absorption by P doping and optimized surface redox potential by cocatalyst integration, stimulates efficient vectorial charge transfer between PCN and CoNiP and subsequent surface mass exchange. On the other hand, we also demonstrate that the well satisfied band structure of PCN can facilitate the two-electron reaction pathway. This work not only has implications for the potential use of CoNiP-PCN as potential photocatalyst for solar H-2 production, but also offers a new idea for pure water slitting in particulate system.

关键词： Photocatalysis Pure water splitting Metal phosphide g-C3N4 H-2 production H2O2 production

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The truncation and stabilization error in multiphase moving particle semi-implicit method based on corrective matrix: Which is dominant?

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COMPUTERS & FLUIDS 2019年 190卷 254-273页

作者： Duan, Guangtao Yamaji, Akifumi Koshizuka, Seiichi Chen, Bin Univ Tokyo Dept Syst Innovat Bunkyo Ku 7-3-1 Hongo Tokyo 1138656 Japan Waseda Univ Grad Sch Adv Sci & Engn Cooperat Major Nucl Energy Tokyo 1698555 Japan Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The Lagrangian nature of the moving particle semi-implicit (MPS) method brings two challenges: disordered particle distribution and particle clumping. The former can cause large random discretization error for the original MPS models while corrective matrix can effectively reduce such large error to the high-order truncation error. The latter can trigger instability easily and thus some adjustment strategies for stability are indispensable, thereby causing non-negligible stabilization error. The purpose of this paper is to compare the relative magnitude of the truncation and stabilization error, which is of great significance for future improvements. An indirect approach is developed because of the difficulty of separating different error from total error in dynamic simulations. The basic idea is to check whether the total error decreases significantly after the truncation error is further reduced. First, a second order corrective matrix (SCM) is proposed for MPS to reduce the truncation error further, as demonstrated by theoretical error analysis. Second, error analysis reveals that the first order gradient model produces less numerical diffusion than the second order gradient model in interpolation after particle shifting. Then, several numerical examples, including Taylor-Green vortex, elliptical drop deformation, excited pressure oscillation flow and continuous oil spill flow, are simulated to test the variance of total error after SCM is applied. It is found that the SCM schemes basically did not remarkably decrease the total error for incompressible free surface flow, implying that truncation error is not dominant compared to the stabilization error. Therefore, reducing the stabilization error is of more significance in future. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Particle method Second order corrective matrix Error analysis Accuracy Stability Interpolation error

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Development and applicability analyses of ADS-4 entrainment model in large advanced PWR

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NUCLEAR engineering AND DESIGN 2020年 356卷 110379-000页

作者： Wang, Liu Tian, Wenxi Zhang, Peng Zhang, Kui Zhang, Yapei Wang, Mingjun Xiang, Yan Qiu, Suizheng Su, G. H. Chang, Huajian Xi An Jiao Tong Univ Sch Nucl Sci & Technol Shaanxi Key Lab Adv Nucl Energy & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China State Nucl Power Technol R&D Ctr Beijing 102206 Peoples R China Royal Inst Technol KTH S-10691 Stockholm Sweden Tsinghua Univ Beijing 100084 Peoples R China

Two new models of liquid entrainment through a vertical tee branch are proposed based on theoretical analyses and experimental data, which can well predict the test results of the prototype facility of CAP1400 and the scaled down facility of AP1000. Moreover, in order to verify the applicability of the new entrainment models, these models are implemented to RELAP5 through the safety analyses with a 2 in. cold leg SBLOCA in AP1000 comparing with the original RELAP5. The contrastive results show that the RELAP5 with proposed entrainment models has more reasonable results. In addition, the modified RELAP5 can calculate less primary coolant inventory which is more conservative. Besides, the less coolant inventory is accord with the beyond design basis accident test of APEX facility (Advanced Plant Experiment). Therefore, the proposed entrainment models are more appropriate for the ADS-4 entrainment safety analyses in large advanced PWR.

关键词： Large advanced PWR ADS-4 Liquid entrainment LOCA

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Design and performance study on a large-scale hybrid CPV/T system based on unsteady-state thermal model

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SOLAR ENERGY 2019年第Jan.期177卷 427-439页

作者： Wang, Zexin Wei, Jinjia Zhang, Gaoming Xie, Huling Khalid, Muhammad Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Shanxi Peoples R China Tsinghua Univ Sichuan Energy Internet Res Inst Chengdu 610213 Sichuan Peoples R China

A hybrid CPV/T unit designed in this work concentrates solar radiation by a compound parabolic concentrator (CPC) and converts solar energy into electrical and thermal energy by a PV/T module. The CPC eliminating multiple reflections of solar radiation is defined as the 'EMR-CPC' in our previous work, which improves photoelectric and thermal conversion efficiencies. Two similar CPV/T units were tested with two-axis tracking device and south-north single-axis tracking device respectively, and the average photoelectric conversion efficiencies were 13% and 12%. A large-scale south-north tracking hybrid CPV/T system with sunlight collecting area of 810 m(2) was built to explore practical application of this CPV/T unit. The whole-day thermal efficiency and total thermal output of the large-scale hybrid CPV/T system were 55% and 1,730,039 kJ respectively on April 14, 2017. The steady-state and unsteady-state thermal models of the hybrid CPV/T system were established and the energy loss was analyzed. The calculated whole-day comprehensive thermal efficiencies of the unsteady-state thermal model and the steady-state thermal model were 55.3% and 55.0% respectively, which were close to the measurement 55.8%. However, the steady-state thermal model failed to accurately predict the whole-day thermal efficiency variation of the system. In comparison, the unsteady-state thermal model accurately predicts instantaneous thermal efficiency of the system varying with meteorological conditions and its total daily heat output.

关键词： Large-scale CPV/T system South-north tracking Steady-state thermal model Unsteady-state thermal model

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Experimental and theoretical study of pool boiling heat transfer and its CHF mechanism on femtosecond laser processed surfaces

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2019年 132卷 259-270页

作者： Liu, Bin Liu, Jie Zhang, Yonghai Wei, Jinjia Wang, Wenjun Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Mech Engn Xian 710049 Shaanxi Peoples R China

In the present study, the pool boiling heat transfer of micro/nano hierarchically structured surfaces, as well as that of a smooth surface in gas dissolved FC-72 (the subcooling is 1 K) was studied. Femtosecond laser processing was used to fabricate the structured surfaces. It was found that for the surfaces with small processing spacing (LS30 and LS70, where the number after LS specifies the spacing in mu m), the critical heat flux (CHF) showed almost no increase, while the heat transfer coefficient (HTC) was enhanced noticeably compared to that of a smooth surface (SS). For LS100, LS200, LS200-2 (compared to LS200, LS200-2 has the same processing spacing but a much higher peak-to-valley height), LS400 and LS800, both the CHF and HTC were enhanced remarkably compared to those of SS. The maximum HTC enhancement was obtained for LS70, with the HTC being 5.87 times larger than that of SS. The most remarkable increase in the CHF was achieved for L5200-2, with an improvement of 91% relative to that of SS. The liquid supply mechanism at the CHF of the micro/nano hierarchically structured surfaces was investigated. A modified model taking into account the coalesced bubble departure frequency, Jakob number and capillary wicking effects was proposed for CHF prediction. The CHF data from this study and the literature were used to validate the model, and it was found that the predicted results agree quite well with the experimental data within 8%. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Boiling heat transfer Femtosecond laser processing Critical heat flux Micro/nano hierarchically structure

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Effects of non-aqueous solvents on CO₂ absorption in monoethanolamine: Ab initio calculations

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MOLECULAR SIMULATION 2018年第10期44卷 815-825页

作者： Zhang, Tingting Yu, Yunsong Zhang, Zaoxiao Xi An Jiao Tong Univ Sch Chem Engn & Technol State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

Monoethanolamine (MEA) is the most typical alkanolamine and its aqueous solutions are widely used for CO2 absorption with mature technology, but the regeneration process is energy consuming. To reduce the energy demand, non-aqueous solvents, such as methanol and ethanol are proposed to substitute water in amine solutions. To understand the influence of the aqueous and non-aqueous solvents on CO2 capture process, the chemical reactions of MEA absorbing CO2 were conducted via ab initio calculations. The non-aqueous solvents discussed in this paper are methanol, ethanol, 1-propanol and 2-propanol. The reaction patterns were investigated and energy barriers were observed. The results show that zwitterion formation and the followed intermolecular hydrogen transfer are proven to be the most possible reaction pattern in both aqueous and non-aqueous solvents. The energy analysis shows that the forward reaction energy barriers increase while the backward barriers decrease as the solvent changes from water to methanol, ethanol, 1-propanol and 2-propanol in turn. The decreases of the energy barriers for backward processes are much higher than the corresponding increases for forward processes. These results indicate that lower energies are required in non-aqueous solvents than in water during the desorption reactions and the non-aqueous solvents are very promising to reduce the regeneration energy consumption in MEA capturing CO2 process. Moreover, the reaction energy gaps between different solvation effects were found to have linear relationship with the logarithm of the dielectric constant difference, which could provide an easy way to theoretically predict the reaction energies of monoethanolamine absorbing CO2 in other solvation effect and can be used to screen appropriate CO2 capture solvent.

关键词： CO2 absorption non-aqueous solvation effect molecular simulation energy gaps dielectric constant

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