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Upgrading the wood vinegar prepared from the pyrolysis of biomass wastes by hydrothermal pretreatment

ENERGY 2022年第PartA期244卷 122631-122631页

作者： Xu, Jiaqing Zhang, Shouyu Shi, Yue Zhang, Peizheng Huang, Dongdong Lin, Chunyu Wu, Yuxin 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 Tsinghua Univ Dept Thermal Engn Beijing 100084 Peoples R China

Hydrothermal pretreatment (HT) is an effective method to upgrade biochar pellets, while little attention is paid to wood vinegar (WV), the byproduct of biochar pellets production. Therefore, Chinese fir sawdust (FS) and cotton stalk (CS) were hydrothermally pretreated first at 180e280 degrees C and then pyrolyzed at 350 degrees C in the study. The effect of hydrothermal pretreatment on the properties of biomass was evaluated by the Van Soest method and thermogravimetric method. The yield, pH, density, and composition of WV were analyzed. The results showed that hemicellulose and cellulose were completely decomposed at HT temperatures of 230 degrees C and 280 degrees C respectively. The removal of hemicellulose and the enrichment of cellulose and lignin in the samples pretreated before 230 degrees C result in a higher density and lower pH of WV, while the yield only increases before 200 degrees C. Compared with CS samples, the higher content and reactivity of cellulose, especially amorphous cellulose, and lignin in FS samples results in the higher yield of the organic compounds in FSWV. With HT temperature increasing to 230 degrees C, the content and yield of acids in FSWV/CSWV shows a declining trend, and the content and yield of phenols, ketones, and aldehydes increase. HT pretreatment below 230 degrees C can upgrade WV. (C)& nbsp;2021 Elsevier Ltd. All rights reserved.

关键词： Biomass wastes Hydrothermal pretreatment Pyrolysis Wood vinegar Chemical components

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Fates of the components in cotton stalk during the hydrothermal oxidative pretreatment and its relationship with the upgrading of biochar pellets and wood vinegar

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FUEL 2022年 320卷 123881-123881页

作者： Xu, Jiaqing Zhang, Shouyu Zhang, Peizheng Shi, Yue Huang, Dongdong Lin, Chunyu Wu, Yuxin 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 Tsinghua Univ Dept Thermal Engn Beijing 100084 Peoples R China

In the present study, biochar pellets and wood vinegar are prepared from the cotton stalk (CS) through the densification and pyrolysis, and hydrothermal oxidative (HO) pretreatment (160-260 degrees C) is conducted to CS to upgrade the quality of biochar pellet and wood vinegar (WV). The results show that HO pretreatment can decompose the hemicellulose, amorphous cellulose, crystalline cellulose, and lignin at 160-230 degrees C, 160-200 degrees C, 200-260 degrees C, and < 200 degrees C, respectively. Therefore, the hemicellulose and cellulose (especially the crystalline cellulose) in CS are enriched at 160-180 degrees C and 160-200 degrees C respectively. Due to the enrichment of hemicellulose and cellulose, the organic compounds in WV increase dramatically after HO pretreatment, resulting in a significant increase in the density and acidity of WV. Furthermore, due to the enrichment of hemicellulose and cellulose, the biochar pellets exhibit more densified internal structures after HO pretreatment, contributing to a higher relaxation density, energy density, and compressive strength. Moreover, the biochar pellets exhibit better combustion performance and lower ash content after HO pretreatment at 160-180 degrees C. The CS sample pretreated at 180 degrees C is the best material for the production of biochar pellets and WV.

关键词： Cotton stalk Hydrothermal oxidative pretreatment Pyrolysis Biochar pellets Wood vinegar

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Enhancing Vertical-Axis Tidal Turbines with Strategic Superhydrophobic Surfaces for Optimized Aerodynamic and Self-Starting Performances

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SSRN 2024年

作者： Yin, Dawei Sun, Jinjing School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Power Energy in Multiphase Flow and Heat Transfer Shanghai200093 China

As observation and research on nature deepen, bionic and hydrophobic surface drag reduction are gaining increasing popularity among researchers. The application of bionic principles and hydrophobic surface technologies in the field of fluid dynamics has opened up new avenues for enhancing the performance of various engineering systems, including vertical-axis tidal turbines (VATTs). By mimicking the natural mechanisms observed in certain species, such as the lotus effect, researchers have been able to develop superhydrophobic surfaces (SHS) that significantly reduce drag in fluid ***, SHS have been applied uniformly across the entire surface of an airfoil. However, this study takes a more nuanced approach by investigating the impact of SHS application at different positions on the airfoil. Through numerical simulations, the study explores how varying the distribution of SHS can influence the power coefficient (Cp), a key performance metric for VATTs . The findings from the study are quite revealing. At a tip speed ratio (TSR) of 1.68, the study observes that applying SHS to 30% of the chord length near the leading edge of the airfoil yields the maximum relative power coefficient benefit, with an increase of up to 34.8%. This suggests that strategic placement of SHS can lead to significant performance improvements without the need for uniform application, which could potentially reduce material costs and maintenance requirements. Moreover, the study also finds that applying SHS only on the inner surface of the VATT can result in a 32% increase in the power coefficient. This indicates that the inner side of the airfoil, which experiences the higher pressure side of the fluid flow, is particularly sensitive to the drag reduction effects of SHS. The leading edge of the airfoil is another critical area where SHS application can have a substantial impact. The leading edge is the first point of contact between the airfoil and the fluid, and any reduc

关键词： Drag reduction

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Study on the influence of distributed Joule-Thomson effect on the performance of microchannel cryocooler

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APPLIED THERMAL engineering 2022年 213卷

作者： She, Hailong Cui, Xiaoyu Weng, Jianhua Chang, Zhihao Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Key Lab Multiphase Flow & Heat Transfer Shanghai P Shanghai 200093 Peoples R China Shanghai Univ Elect Power Sch Energy & Mech Engn Shanghai 200090 Peoples R China

At present, the pros and cons of distributed Joule-Thomson (J-T) effect in throttling refrigeration systems have been controversial. In this paper, a microchannel J-T cryocooler is used as the prototype. The distributed J-T effect is produced by the friction loss in the throttling channel. The refrigeration performance of the cryocooler at 6.0 MPa is analyzed. Then, according to the dependence of the J-T coefficient on pressure and temperature, a fully distributed J-T effect microchannel is designed to replace the separate counterflow heat exchanger and throttling device on the high-pressure side. The characteristics are simulated and compared with the prototype. The results show that the refrigeration ability of the fully distributed J-T cryocooler is slightly inferior to that of the prototype under the same pressure drop, and excessively increasing or reducing the cross-sectional size of the channel is not conducive to cooling. However, the fully distributed J-T effect structure can effectively delay the occurrence of choked flow due to the low velocity of the fluid. Under 6.0 MPa inlet pressure, the limited massflow rate of fully distributed cryocooler is 7.51 g/s, and the lowest temperature can reach 147.7 K, which is significantly lower than 163.3 K that the prototype can reach in the choked state. In addition, this paper also explores the influence of distributed J-T effect on the low-pressure side, which is beneficial to precooling the high-pressure fluid more efficiently using a little distributed J-T effect. A proper part of the friction loss in the low-pressure channel helps improve the refrigeration ability. At 6.0 MPa inlet pressure, the best cooling effect is obtained when the pressure drops in the low-pressure channel account for 15.85 % of the total pressure drop.

关键词： Distributed J-T effect Microchannel heat exchange and throttling Choked flow

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Pore-scale simulation of miscible displacement in an inclined porous medium

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FRONTIERS IN ENERGY RESEARCH 2024年 12卷

作者： Liu, Gaojie Xu, Aoyu Wang, Yongqiang Lou, Qin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China

Introduction: This study investigates the displacement of two miscible fluids within an inclined porous medium at the pore scale, highlighting how the pore-scale microstructure, inclination angle, and viscosity ratio affect the interfacial instability between two fluids during displacement processes. Methods: The lattice Boltzmann Method (LBM) is employed to solve the governing equations. Two distribution functions are used to simulate the velocity field and the concentration field, respectively. Results and discussion: An increase in inclination angle exacerbates the interfacial instability between fluids and the viscous fingering phenomenon. This viscous fingering expands the sweep range of displacing fluids, which improves the displacement efficiency. When theta > 50(degrees), further increase in inclination angle will not cause significant changes in displacement efficiency. In addition, the viscosity ratio is a key factor affecting displacement efficiency. The larger the viscosity ratio, the greater the displacement efficiency. Furthermore, the critical viscosity ratio has been found, and any increase in the viscosity ratio above the critical value will not affect the displacement efficiency.

关键词： miscible displacement viscous fingering inclined porous media displacement efficiency lattice Boltzmann method

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Effect of copper metal foam proportion on heat transfer enhancement in the melting process of phase change materials

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APPLIED THERMAL engineering 2022年第PartB期201卷 117778-117778页

作者： Wang, Zilong Zhang, Hua Dou, Binlin Zhang, Guanhua Wu, Weidong Zhou, Xiang Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Tongji Univ Sch Mech Engn 204 Jiyang Bldg1239 Siping Rd Shanghai 200092 Peoples R China

Phase change materials can overcome the low energy density and utilisation efficiency of solar energy. However, the low thermal conductivity of phase change materials significantly affects the thermal efficiency of solar devices;thus, improving the thermal conductivity of phase change materials has been the focus of many recent studies. Using paraffin wax and copper metal foam, copper metal foam composite phase change materials were prepared in this study. The effect of the copper metal foam proportion on heat transfer enhancement in the melting process of phase change materials was analysed using visualisation heat storage experimental equipment. The integrated heat transfer coefficient of the copper metal foam composite phase change materials was obtained. The experimental results showed that as the copper metal foam proportion increased from 0% to 2.13%, the melting time of the copper metal foam composite phase change materials decreased from 901 s to 791 s, and the heat storage rate and integrated heat transfer coefficient increased from 21.81 J/s to 25.08 J/s and 1.26 W/(m K) to 4.16 W/(m K), respectively. The heat storage capacity first increased and then decreased. The minimum temperature gradient of 5.2 K was reached when the copper metal foam proportion was 2.13%. More important, natural convection is the major heat transfer mechanism in the melting process of composite phase change materials with a low copper metal foam proportion;heat conduction plays a primary role in the melting process of composite phase change materials with a high copper metal foam proportion. The best heat storage and heat storage rate for copper metal foam composite phase change materials were 20260.49 J and 24.38 J/s, respectively, achieved with a copper metal foam proportion of 1.28%.

关键词： Copper metal foam Phase change materials heat transfer enhancement Integrated heat transfer coefficient heat storage property

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Preparation and assessment of a novel hydrated salt PCM applied for intermittent floor radiant heating systems

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JOURNAL OF ENERGY STORAGE 2025年 105卷

作者： Liu, Jie Yang, Yingying Li, Aizheng Wang, Wensong Wu, Weidong 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

Intermittent floor radiant heating is widely employed in building heating systems. However, it suffers large indoor air temperature fluctuations due to its intermission. The integration of phase change material (PCM) can significantly mitigate this issue. In this study, Na2HPO4 & sdot;12H2O and Na2SO4 & sdot;10H2O were used as raw materials, with expanded perlite (EP) as the porous medium, to prepare a shaped composite phase change material (EPPCM). This material was then blended into mortar to produce a novel phase change mortar (EPPCM-M). Experiments were carried out to evaluate its heat storage performances. Compared to normal mortar, EPPCM-M of 25 mm thickness mitigates temperature fluctuations, with the peak temperature on the cold end reduced by about 2.5 degrees C and a slower cooling rate on the hot end. To assess the practical application of EPPCM in buildings, a simulation study was conducted. A room model of 4 x 4 x 3 m was built and subjected to radiant floor heating for 8 h daily, under the winter climate conditions of shanghai from November 15th to March 14th. The results showed that the EPPCM-M can effectively suppress temperature fluctuations in both the floor surface and average indoor air temperatures. From February 27th to March 5th, the maximum fluctuation of floor surface temperature was reduced by 55.4 %, the maximum fluctuation of average indoor air temperature was reduced by 39.5 %. The application of the EPPCM-M in intermittent floor radiant heating not only ensures indoor thermal comfort but also achieves heat's "peak load shifting", improving indoor comfort, reducing heating energy consumption, and promoting building energy efficiency.

关键词： Phase change material Thermal storage performance Intermittent floor radiant heating system Numerical simulation

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Insights on CDI parametric controls and dependencies using gloabal sensitivity analysis

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SEPARATION AND PURIFICATION TECHNOLOGY 2025年第Part8期354卷

作者： Qin, Huai Fang, Fang Mao, Yunfeng Xu, Longqian Wu, Deli 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 Zhejiang Prov Ind EP Design & Res Inst Co Ltd Shangyu 310013 Zhejiang Peoples R China Tongji Univ Coll Environm Sci & Engn State Key Lab Pollut Control & Resources Reuse Shanghai 200092 Peoples R China Vanderbilt Univ Dept Civil & Environm Engn Nashville TN 37235 USA

Capacitive deionization (CDI) emerges as a promising desalination technology due to its high energy efficiency and potential for energy recovery. Its performance improvement and application extension highly require understanding how variations in multiple input parameters, as well as their interactions, lead to variations in output, which is not straightforward in the complex system of CDI. In this work we use the extended Fourier amplitude sensitivity test (eFAST) method to conduct a global sensitivity analysis (GSA) in order to examine the effects of several parameters, including material properties, operating conditions, and ionic properties, on the energy consumption and salt removal efficiency of CDIs. The research reveals that high capacitance and efficient mass transfer are crucial for CDI advancement, with a trade-off between desalination rate and energy efficiency. The interplay between input parameters is revealed by factorial design and GSA, which show that no single parameter alone determines salt adsorption capacity but that feedwater salt concentration and current density are important when considering both individual and coupled effects. The study suggests that the specific application and feedwater characteristics should be taken into consideration when deciding between the CC and CV modes of desalination. While CC mode excels in water production and energy efficiency for high salinity feedwater pretreatment, CV mode is better at treating low salinity waterr. The comprehensive parametric analysis provides valuable insights into optimizing CDI design and operating conditions to balance desalination capacity and energy efficiency.

关键词： Capacitive deionization Mass transfer model Global sensitivity analysis Constant current mode Constant voltage mode

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Study on the Three-Dimensional flow Control of Two-Phase flow Around a Cylinder by an Attached Cylinder

SSRN

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SSRN 2023年

作者： Xia, Yizhan Hu, Yu Huang, Shengxian 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

Enhancing the separation of flow, shedding of vortices, and sediment deposition around blunt bodies, particularly in cylindrical flows within the realm of ocean engineering, emerges as a pivotal safety factor. This study delves into the control of two-phase flow encircling a cylinder using an affixed cylinder under three-dimensional real ocean conditions. Employing the SST turbulence model, a two-dimensional incompressible RANS numerical simulation is performed. Initially, the influence of varying gap ratios between the auxiliary small cylinder and the main cylinder is scrutinized. Subsequently, the impact of attached small cylinders on the flow field surrounding the main cylinder is examined under different particle characteristics. Lastly, employing the UDF function, four small cylinders exhibiting distinct vibration modes are defined, and the numerical simulation investigates the effects of Grain flow on particle flow and distribution in the wake region of the main cylinder. © 2023, The Authors. All rights reserved.

关键词： Cylinders (shapes)

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Melting characteristics and dynamic evolution of microstructure of single-crystal gold film irradiated by laser under the non-Fourier effect

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MOLECULAR CRYSTALS AND LIQUID CRYSTALS 2021年第1期723卷 62-79页

作者： Wang, Qing Li, Ling Yang, Mo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

The process of ultra-thin single crystal gold film irradiated by femtosecond laser is simulated by the combination of improved two-temperature model (TTM) and molecular dynamics (MD). The results indicate that under the non-Fourier effect, the gold film shows special melting characteristics and spalling mechanism. The phenomena of homogeneous melting and pore spalling of gold film are successfully distinguished by curing rate method and atomic density method respectively. Due to the tiny thickness of the gold film studied, the damage mechanism of the gold film irradiated by laser has also changed.

关键词： Femtosecond laser melting characteristics metal film non-Fourier effect spalling damage

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