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Multiplicity of thermodynamic states of van der Waals gas in nanobubbles

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Chinese Journal of Chemical Engineering 2021年第3期34卷 26-32页

作者： Xu Tang hongguang zhang Zhenjiang Guo Xianren zhang Jing Li Dapeng Cao State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China

The gas-containing nanobubbles have attracted extensive attention due to their remarkable properties and extensive application ***,a number of fundamental aspects of nanobubbles,including thermodynamic states for the confined gas,remain still *** we theoretically demonstrate that the van der Waals(vd W)gases confined in nanobubbles exhibit a unique thermodynamic state of remarkably deviating from the bulk gas phase,and the state transition behavior due to the sizedependent Laplace *** general,the vd W gas inside nanobubbles present multiple stable or transient states,where 0–2 states are for supercritical gas and 0–4 for subcritical *** further analysis based on Rayleigh–Plesset equation and free energy determination indicates that the gas states in nanobubbles exhibits different levels of stability,from which the coexistence of multiple bubble states and microphase equilibrium between droplets and bubbles are *** work provides insight to understand the thermodynamic states appeared for gas in nanobubbles.

关键词： Nanobubbles Stability Thermodynamics Kinetics

Study on the Performance of Organic Rankine Cycle-Heat Pump(ORC-HP) Combined System Powered by Diesel Engine Exhaust

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Journal of Thermal Science 2019年第5期28卷 1065-1077页

作者： ZHAO Tenglong YU Fei zhang hongguang WU Yuting WANG Yan College of Environmental and Energy Engineering Beijing University of Technology Beijing 100124 China MOE(Ministry of Education)Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy Conversion Beijing University of Technology Beijing 100124 China

This study presents an ORC-HP combined system driven by diesel engine exhaust. This paper focuses on the feasibility and performance of the combined system under heating mode to heat a coach. The performances of the combined system with different parameters, including condensation temperature and evaporation pressure in ORC system, gas cooler outlet pressure, gas cooler outlet temperature and evaporation temperature in HP system, have been analyzed. The results show that the combined system can fully meet the demand of heat production. The optimal flow division ratio(rp) of 0.32 is selected by analyzing the system performance. Low condensation temperature is beneficial to the combined system performance. There exists a suitable range of evaporation temperature, gas cooler outlet pressure and gas cooler outlet temperature to achieve excellent performance. The heating coefficient of performance(COP_h) shows a first increasing and then decreasing trend with gas cooler outlet pressure, namely there exists an optimal gas cooler outlet pressure that achieves the maximum COP_h. The maximum total efficiency, COP_h and heating capacity can reach up to 48.44%, 4.78 and 176.56 kW, respectively. These results show significant energy savings by applying the ORC-HP combined system.

关键词： organic Rankine cycle heat pump combined system total efficiency COPh

Multi-Objective Particle Swarm Optimization(MOPSO) for a Distributed Energy System Integrated with Energy Storage

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Journal of Thermal Science 2019年第6期28卷 1221-1235页

作者： zhang Jian CHO Heejin MAGO Pedro J. zhang hongguang YANG Fubin Mechanical Engineering Department Mississippi State UniversityMississippi StateMS39762USA College of Environmental and Energy Engineering Beijing University of TechnologyBeijing 100124China

Distributed energy systems are considered as a promising technology for sustainable development and have become a popular research topic in the areas of building energy systems. This work presents a case study of optimizing an integrated distributed energy system consisting of combined heat and power(CHP), photovoltaics(PV), and electric and/or thermal energy storage for a hospital and large hotel buildings located in Texas and California. First, simulation models for all subsystems, which are developed individually, are integrated together according to a control strategy designed to satisfy both the electric and thermal energy requirements of a building. Subsequently, a multi-objective particle swarm optimization(MOPSO) is employed to obtain an optimal design of each subsystem. The objectives of the optimization are to minimize the simple payback period(PBP) and maximize the reduction of carbon dioxide emissions(RCDE). Finally, the energy performance for the selected building types and locations are analyzed after the optimization. Results indicate that the proposed optimization method could be applied to determine an optimal design of distributed energy systems, which reaches a trade-off between the economic and environmental performance for different buildings. With the presented distributed energy system, a peak shaving in electricity of about 300 kW and a reduction in boiler fuel consumption of 610 kW could be attained for the hospital building located in California for a winter day. For the summer and transition seasons, electricity peak shaving of 800 kW and 600 kW could be achieved, respectively.

关键词： multi-objective particle swarm optimization distributed energy system payback period carbon dioxide emission

Exogenous application of succinic acid enhances tolerance of Larix olgensis seedling to lead stress

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Journal of Forestry Research 2018年第6期29卷 1497-1505页

作者： Jinfeng Song hongguang zhang Chengwei Duan Xiaoyang Cui School of Forestry Northeast Forestry University Maoershan Forest Research Station Northeast Forestry University

Larix olgensis A. Henry(Changbai larch) is a productive commercial species and good candidate for afforestation in northeast China. It is widely planted in lead-stressed soils which can induce oxidative damage in this plant. Increasing tolerance to lead(Pb) stress is therefore of keen interest. A greenhouse experiment was conducted to identify the biomass, physiological responses and Pb accumulation of L. olgensis seedlings to Pb stress under succinic acid(SA) application and to explore the interaction of exogenous SA applications and stress resistance. L. olgensis seedlings were planted in Pb-stressed or unstressed haplic cambisols in pots. In Pb-contaminated soils the seedlings were treated daily with concentrations of SA solutions at a rate approximately equivalent to 0, 0.04,0.2, 1.0, or 2.0 mmol kg-1of soil for 10, 20, and 30 days,respectively. Pb treatment induced damage in the seedlings and led to the inhibition of biomass accumulation in roots,stems and leaves, and a rise in Pb accumulation in fine roots and leaves. Malondialdehyde(MDA) content and electrolyte leakage in leaves significantly increased while peroxidase(POD) activities, soluble protein and photosynthetic pigment contents in leaves were all *** toxicity was promoted with increasing Pb treatment times. When Pb-stressed seedlings were exposed to SA(especially 10.0 mmol L-1 over 20 days), the physiological responses for Pb-only were reversed and the biomass of roots, stems, and leaves dramatically *** facilitated Pb uptake in fine roots and leaves but more Pb accumulated in fine roots. The results demonstrate that exogenous SA alleviates Pb-induced oxidative injuries and improves the tolerance of L. olgensis seedlings to Pb stress.

关键词： Soil Pb stress Succinic acid Larix olgensis Physiological response Pb uptake

Construction of spontaneously polarized ceramic via synergistic mechanical activation-Biomimetic mineralization for activating air and water

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Journal of Materials Science & Technology 2023年第34期165卷 132-142页

作者： Wuxiang zhang hongguang zhang Ying Zhu Zuqiang Huang Yanjuan zhang Tao Gan Huayu Hu Yuben Qin School of Chemistry and Chemical Engineering Guangxi UniversityNanning 530004China Key Laboratory of New Low-carbon Green Chemical Technology Education Department of Guangxi Zhuang Autonomous RegionNanning 530004China

Spontaneously polarized crystals with intrinsic electric dipole moment have attracted immense interest as excellent functional materials for extensive *** is of great significance to engineer sustainable spontaneously polarized materials with fascinating characteristics and performance for activating air and ***,a novel strategy based on the synergy of mechanical activation(MA)and biomimetic mineralization(BM)was created to construct spontaneously polarized *** induced the structural damage of clay and promoted the dissolution of ions and the release of free proteins,contributing to the formation of silicate precursor in BM *** high temperature firing,the silicate precursor in clay was converted to form KCa_(3)AlCa_(3)Si_(4)O_(16)(hexagonal crystal system,L^(6)symmetry type,and P63 space group)in the resulting spontaneously polarized *** non-centrosymmetric structure of KCa_(3)AlCa_(3)Si4O_(16)and the high intrinsic electric dipole moments contributed by K(1)polyhedrons resulted in high spontaneous polarization(0.2322μC/cm^(2))and far-infrared emissivity(0.951)of spontaneously polarized *** air,spontaneously polarized ceramic can activate H_(2)O and O_(2)molecules to form negative air ions owing to surface electric *** water,spontaneously polarized ceramic can disaggregate large water clusters to form small water clusters ascribed to surface electric field and far-infrared emission;water pH can be regulated from weak acidity to approximate neutrality via the capture of electrons by H+ions to produce releasable hydrogen *** work provides great promise for rational design and synthesis of spontaneously polarized materials for functional applications.

关键词： Ceramic Spontaneous polarization Mechanical activation Biomimetic mineralization Activation of air and water

Microdroplet targeting induced by substrate curvature

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Chinese Physics B 2018年第9期27卷 450-456页

作者： hongguang zhang Zhenjiang Guo Shan Chen Bo zhang and Xianren zhang State Key Laboratory of Organic-Inorganic Composites Belting University of Chemical TechnologyBelting 100029China

Fundamental understanding of the wettability of curved substrates is crucial for the applications of microdroplets in colloidal science, microfluidics, and heat exchanger technologies. Here we report via lattice Boltzmann simulations and energetic analysis that microdroplets show an ability of transporting selectively to appropriate substrates solely according to substrate shape（curvature）, which is called the substrate-curvature-dependent droplet targeting because of its similarity to protein targeting by which proteins are transported to the appropriate destinations in the cell. Two dynamic pathways of droplet targeting are identified： one is the Ostwald ripening-like liquid transport between separated droplets via evaporating droplets on more curved convex（or less curved concave） surfaces and growing droplets on less curved convex（or more curved concave） surfaces, and the other is the directional motion of a droplet through contacting simultaneously substrates of different curvatures. Then we demonstrate analytically that droplet targeting is a thermodynamically driven process. The driving force for directional motion of droplets is the surface-curvature-induced modulation of the work of adhesion, while the Ostwald ripening-like transport is ascribed to the substrate-curvature-induced change of droplet curvature radius. Our findings of droplet targeting are potentially useful for a tremendous range of applications, such as microfluidics, thermal control, and microfabrication.

关键词： droplet targeting substrate curvature lattice Boltzmann simulation

Performance Analysis of a Multistage Centrifugal Pump Used in an Organic Rankine Cycle(ORC) System under Various Condensation Conditions

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Journal of Thermal Science 2019年第4期28卷 621-634页

作者： YANG Yuxin zhang hongguang TIAN Guohong XU Yonghong WANG Chongyao GAO Jianbing College of Environmental and Energy Engineering MOE (Ministry of Education) Key Laboratory of Enhanced Heat Transfer and Energy ConservationBeijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China Collaborative Innovation Center of Electric Vehicles in Beijing Beijing 100124China Department of Mechanical Engineering Sciences University of SurreyGuildford GUI 2LJUK School of Electrical and Mechanical Engineering Beijing Information Science and Technology UniversityBeijing 100192China

In an organic Rankine cycle(ORC)system,the working fluid pump plays an important role in the system *** paper focused on the operating characteristics of a multistage centrifugal pump at various speeds and condensation *** experimental investigation was carried out to assess the influence of the performance of the pump by the ORC system with special attention to actual net power output,thermal efficiency as well as back work ratio(BWR).The results showed that an increase in the pump speed led to an increase in the mass flow rate and expand in the operating range of the outlet *** mass flow rate decreased nonlinearly with the increase of the outlet pressure from 0.22 to 2.41 MPa;the electric power consumption changed between 151.54 and 2409.34 W and the mechanical efficiency of the pump changed from 7.90%to 61.88%when the pump speed varied from 1160 to 2900 r/***,at lower pump specific speed the ORC system achieved higher thermal efficiency,which suggested that an ultra-low specific speed pump was a promising candidate for an ORC *** results also suggested that the effects of condensation conditions on the pump performance decreased with the pump speed increasing and BWR was relatively sensitive to the condensation conditions,especially at low pump speed.

关键词： waste heat recovery organic Rankine cycle multistage centrifugal pump operating characteristics various condensation conditions back work ratio(BWR)

Fabrication of Al_2O_3-NaCl Composite Heat Storage Materials by One-step Synthesis Method

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Journal of Wuhan University of Technology(Materials Science) 2016年第5期31卷 950-954页

作者：朱教群李儒光 ZHOU Weibin zhang hongguang CHENG Xiaomin State Key Laboratory of Silicate Materials for Architectures Wuhan University of Technology Wuhan 430070 China School of Material Science and Engineering Wuhan University of Technology Wuhan 430070 China

Thermal energy storage is an attractive option for effectiveness since it gives flexibility and reduces energy consumption and costs. New composite materials for storage and transformation of heat of NaCl-Al2O3composite materials were synthesized by one-step synthesis method. The chemical composition, morphology, structure, and thermal properties were investigated by XRD, EDS, SEM, and DSC. The results show that NaCl can be absorbed by Al2O3particle from 800 to 900 ℃ for Al2O3particle surface is rich active structure. The results also indicate that the leakage of NaCl when the phase change can be prevented by Al2O3particles and the enthalpy of phase change of NaCl-Al2O3material is 362 J/g. The composites have an excellent heat storage capacity. Therefore, this study contributes to one new thought and method to prepare high temperature heat storage material and this material can be applied in future thermal engineering.

关键词： one-step synthesis composite materials heat storage

Study of Shifted UV Emission Peak of ZnO Nanowire Arrays

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Journal of Wuhan University of Technology(Materials Science) 2022年第6期37卷 1048-1050页

作者： LIU Liqing LI Yongtao HE Xuemin zhang hongguang SHEN Jianping New Energy Technology Engineering Laboratory of Jiangsu Province&School of Science Nanjing University of Posts and Telecommunications(NJUPT)Nanjing 210023China College of Electronic and Optical Engineering Nanjing University of Posts and TelecommunicationsNanjing 210023China

We have obtained vertically aligned ZnO nanowire arrays synthesized by microwave-assisted heating method with different growth *** the room-temperature PL measurement,the strong deep-level emission and weak near band edge(NBE)emission can be *** deep-level emissions became weaker and deep-level emissions became stronger when the samples were annealed at 300℃for 30 min,meanwhile,the NBE emission peaks get red-shifted with growth time,and the longer the growth time,the more the peak *** phenomenon can be attributed that the diameter of ZnO nanowires increases with growth *** PL emission phenomenon is important in research of optoelectronic application.

关键词： ZnO nanowire arrays photoluminescence property red shift different growth time