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Numerical Investigation of the Thermal Response to Skin Tissue during Laser Lipolysis

Journal of Thermal Science 2018年第5期27卷 470-478页

作者： CHEN Bin ZHANG Yue LI Dong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Laser lipolysis can effectively treat obesity and its associated diseases, such as hypertension, fatty liver, and hyperlipidemia. However, currently available invasive laser lipolysis, which transmits laser to a fiber-optic catheter inserted into the subcutaneous tissue for irradiation through an incision, may cause hematomas, infections, and empyrosis. The current study presents a novel, noninvasive approach for laser lipolysis, which directly irradiates the intact skin surface without an incision and preferentially targets adipose tissue at the near-infrared band. High laser energy is necessary to damage adipocytes; however, this may carbonate and burn the dermis. Therefore, the introduction of skin cooling is essential to avoid unwanted hyperthermal injury and improve the threshold of radiant exposure. In the current study, we investigated a novel noninvasive approach assisted with skin cooling by establishing a homogeneous multi-layer skin model. In this method, light propagation in the skin was simulated by using the Monte Carlo method. Skin cooling was employed before laser irradiation to protect the epidermis from thermal damage, which was treated as a boundary condition based on Newton's law. The numerical results showed that the photons were deposited in the adipose layer more than in the other layers. Laser can effectively destroy adipose tissue at an energy density of >200 J/cm^2 at 1210 nm wavelength, whereas at least 300 J/cm^2 is required at 1064 nm to achieve the same effect. In this experiment, at >5 s pulse width, the selectivity of adipose was not obvious. Moreover, the results indicated that 60 ms R134a or R404a spray can effectively reduce the temperature of the epidermis. R404a exhibited a stronger cooling effect than R134a. Cold air cooling at -10 °C for 10 s could effectively decrease the skin temperature, and deeper cooling could be achieved by cold air cooling compared with cryogen spray cooling.

关键词： laser lipolysis Nd：YAG laser multi-layer skin model skin cooling

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Phenomenon of fog formation and flow characteristics of droplet-vapor-gas mixture in a cooler-condenser

Phenomenon of fog formation and flow characteristics of drop...

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ASME 2019 International Mechanical engineering Congress and Exposition, IMECE 2019

作者： Gu, Hongfang Guo, Qiwei Li, Changsong Zhou, Qing State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi China

ISBN: (纸本)9780791859452

Fog formation occurs in the process of condensation in the presence of non-condensable gas if the bulk temperature is lower than its saturation temperature (supersaturated). The phenomena of fogging is the formation of small condensate particles mixing with the vapor/gas stream, which creates potential problems of the vapor/gas/condensate separation and environmental pollution. Therefore, understanding of fogging mechanism and prevention of fog droplet entrainment are one of technical concerns for design and operation of cooler-condensers in the process industry. This paper presents the experimental study and numerical simulation of shell-side condensation with fog formation using a mixture of steam/non-condensable gas. The experimental data were collected on the two tube bundles (modified plastic tubes and stainless steel tubes). Using a high-speed photograph technique, the phenomenon of fog formation and flow characteristics of vapor/droplet transport were recorded over a wide range of test conditions. The numerical analysis of film and dropwise condensation, fog formation and droplet particle transport were simulated using different tube geometry and material, and flow velocity of air/droplet mixture. Based on simulation results, a new droplet trapping parameter is proposed to assess the optimal parameters of heat exchanger structural and operation conditions. Comparisons show that the numerical analysis results have a good agreement with experimental data and observations. These findings provide fundamental approach to account for the effect of fog formation, film and dropwise condensation, and droplet transport crossflow in cooler-condensers. Copyright © 2019 ASME.

关键词： Drops

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Melt droplet fragmentation behavior during fuel-coolant interaction 18

Melt droplet fragmentation behavior during fuel-coolant inte...

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18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019

作者： Li, Gen Feng, Haobo Wen, Panpan Zhang, Jun Wang, Jinshi Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

During a severe accident of nuclear reactor, the fuel-coolant interaction occurs at the relocation stage of corium melt. Such a mode of contact can result in vigorous thermal interactions, intense steam generation and, potentially, steam explosions. The thermal processes, in their turn, largely depend on hydrodynamic behavior. When melt is pouring into coolant pool, the melt jet fragments into large droplets or blobs, named the primary breakup. The droplets or blobs will experience secondary breakup as a result of shock wave at steam explosion. Either the primary or secondary breakup is governed by interface hydrodynamic instabilities. The droplet size distribution, which affects fuel-coolant areas, is important for evaluating heat transfer and debris coolability. In this study, we modelled melt drops deformation and fragmentation using a meshless Lagrangian MPS method. Fragments amount and size distribution were compared under different Weber numbers, and fragments drag coefficient were also analyzed. The results indicate that the melt drops breakup process could be divided into two phases: initial deformation and fragmentation phase governed by flow inertial force and the subsequent fragments coalescence phase under the impact of fluid surface tension. Fragments amount increased in fragmentation phase but decreased in coalescence phase. A large amount of fragments has a normalized diameter of 0.01 - 0.03, but a small amount of large size fragments (d/d0 > 0.04) also appeared as the crescent-shaped melt broke up and small fragments coalesced. The drag coefficient decreased with time during drop deformation period, and then reached a stable value. It has no significant difference among cases with different Weber numbers. © 2019 American Nuclear Society. All rights reserved.

关键词： Hydrodynamics

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Experimental study of auto-ignition of dimethyl ether at low-temperatures and low-pressures 12

Experimental study of auto-ignition of dimethyl ether at low...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Huang, Wenlin Sun, Wuchuan Wu, Honghuan Qin, Xiaokang Jiang, Xue Zhang, Yingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Dimethyl ether (DME) is a property of alternative fuels to attract due to the special molecular structure in terms of either scientific study or engine application. However, the lack of fundamental data at low pressures and low temperatures impedes to understand thoroughly the chemistry of DME. Ignition delay times of DME/"air" mixtures with various equivalence ratios of 0.5 - 5.0 were measured in a shock tube at pressure of 3.0 atm over temperatures of 625 - 1200 K. Aramco Mech 2.0 was selected to reproduce the experimental observation. In general, the kinetic model remains an uncertainty in predicting the reactivity of DME at equivalence ratios below 2.0 but it tends much better at equivalence ratios over 3.0. Unlike the model predictions, the experimental data did not show obvious NTC behavior for the mixtures with equivalence ratios of 0.5 and 1.0. The selected model almost fails to capture the four-stage ignition feature for the mixtures with equivalence of 2.0 even considering the hot spot caused by pre-ignition energy release. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Ethers

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Effects of Flue Gas Recirculation on Combustion and Heat Flux Distribution in 660 Mw Double-Reheat Tower-Type Boiler

SSRN

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SSRN 2022年

作者： Deng, Lei Dong, Lingxiao Bai, Yang Wu, Yuhao Liu, Hu Belošević, Srdjan Tomanović, Ivan Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Guoshen Institute of Technology CHN ENERGY Xi'An710065 China Department of Thermal Engineering and Energy "VINČA" Institute of Nuclear Sciences National Institute of thе Republic of Serbia University of Belgrade Mike Petrovića Alasa 12-14 11351 Vinča PO Box 522 Belgrade11001 Serbia

The ultra-supercritical double-reheat boiler has attracted more attention because of high parameters, low pollution and large capacity. However, there are some difficulties in the development of this technology, such as adjusting the reheat steam temperature. In this study, computational fluid dynamics simulation is used to analyze a 660 MW double-reheat tower-type pulverized coal-fired boiler. The influence of flue gas recirculation (FGR) on heat transfer characteristics and combustion process in the furnace (including heating surfaces in the upper parts of the furnace) are evaluated. The user-defined function approach predicates CO reduction effect on NO x . The results show that the flow at the horizontal section through the centerline of recirculating flus gas nozzles is rotating. The velocity distribution changes into an elliptical rotating flow when FGR ratio is 20%. At higher FGR ratios, the high-temperature area (1565-1700 K) shrinks and both the NO x concentration at the low-temperature superheater outlet and oxygen concentration in the furnace descend. Oxygen concentration at low-temperature superheater outlet first increases and then decreases. In the main combustion zone, the heat flux peak of water-cooled wall is about 330 kW m -2 . As FGR ratio increases from 0% to 20%, the rate of water-cooled wall heat absorption to total boiler decreases by 3.50%. This rate for reheater and superheater increases by 2.53% and 2.13%, respectively. © 2022, The Authors. All rights reserved.

关键词： Temperature

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Study on the heat and mass transfer characteristics of wet air in metal foam in the space station environment

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Applied Thermal engineering 2025年 277卷

作者： Guowei Zhu Liang Zhang Yujuan Xia Hantao Zhou School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China China National Institute of Standardization Beijing 100191 China

This paper has developed a novel dehumidification device for space station environment, which uses foam copper as the core, with a Stirling refrigerator providing cooling, heat pipes assisting in heat conduction and a siphon water guidance system employed to remove condensate. Experiments on dehumidifying wet air within the foam copper were then carried out under simulated microgravity dehumidification conditions. The experimental conditions included different inlet air temperatures, humidities, air velocities, and cold end temperatures of the Stirling refrigerator. The experimental research indicates that as the inlet air temperature rises from 20 °C to 30 °C, the mass transfer coefficient increases by 57.06 %, and the sensible heat coefficient rises by 10.62 %. When the air velocity increases from 0.4 m·s −1 to 1.4 m·s −1 , these two coefficients increase by 111.79 % and 170.83 %, respectively. In contrast, increasing the relative humidity from 50 % to 80 % results in a 34.09 % decrease in the sensible heat coefficient, while the mass transfer coefficient increases by 11.4 %. When the cold-end temperature rises from 8 °C to 13 °C, the sensible heat transfer and mass transfer coefficients increase by 9.63 % and 4.06 %, respectively. Based on this, a sensitivity analysis was conducted using the experimental data, and heat and mass transfer correlations were fitted. The mean standard deviations of the heat and mass transfer correlations are 3.74 % and 6.30 %, respectively, indicating a high degree of fitting accuracy. This work provides a new humidity control solution for future space station thermal management systems.

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Activated Overall Water Splitting Over a Ni-Fe Layered Double Hydroxide Electrocatalyst by V Doping and Sulfuration

SSRN

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SSRN 2023年

作者： Wu, Wentong Peng, Lei Min, Boya Huang, Jie Liu, Saiya Lu, Kejian Lu, Shijian Jing, Dengwei Zheng, Mingsheng Liu, Maochang International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China No. 8 Oil Production Plant of PetroChina Changqing Oilfield Company Shaanxi Xi’an710016 China Carbon Neutrality Institute Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization China University of Mining and Technology Jiangsu Xuzhou221008 China Gree Altairnano New Energy Inc Zhuhai519040 China School of Chemistry and Biological Engineering University of Science and Technology Beijing Beijing100083 China

Ni-Fe layered double hydroxide (NiFe-LDH) is regarded as one of the promising non-noble electrocatalyst. However, the limited number of active sites and poor electrical conductivity impede its further development. Herein, we report the synthesis of a Ni foam supported NiFe-LDH electrocatalyst modified by V doping and vulcanization (NiFeV-S/NF). This modification endows the catalyst excellent property toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. Only 211 mV and 127 mV of the overpotentials are required to achieve the current density of 10 mA cm-2 for OER and HER in 1 M KOH electrolyte, respectively. Particularly, the prepared NiFeV-S/NF could serve as a bifunctional electrocatalyst for overall water splitting, with a cell voltage of 1.573 V to reach a current density of 10 mA cm-2. In principle, the success relies on the intrinsically improved conductivity, increased specific surface area and the number of active sites, as well as the heterojunction structure of the catalyst. Therefore, this work provides a new idea for the design and preparation of more efficient noble-metal-free bifunctional electrocatalysts. © 2023, The Authors. All rights reserved.

关键词： Electrocatalysts

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Experimental Investigation on Ejector Performance Using R134a as Refrigerant

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Journal of Thermal Science 2019年第4期28卷 727-735页

作者： DAI Zhengshu YU Bo LIU Pengpeng CHEN Guangming ZHANG Hua School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China State Key Laboratory of Air-conditioning Equipment and System Energy Conservation Zhuhai 519070China Institute of Refrigeration and Cryogenics Zhejiang UniversityHangzhou 310027China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China

Ejector refrigeration has the advantage of low capital cost,simple design,reliable operation,long lifespan and almost no *** only weakness is the low efficiency and its intolerance to deviations from design operation condition.R134 a used in ejector refrigeration system gives better performance in comparison with many other environmental friendly refrigerants as the generation temperature is from 75℃to 80℃.The present work experimentally investigated the on-design and off-design performance of the ejector with fixed geometry using R134 a as refrigerant,and cycle performance of the ejector refrigeration *** experimental prototype was constructed and the effects of primary flow inlet pressure,secondary flow inlet pressure and ejector back pressure on ejector performance and cycle performance were investigated *** operation conditions are:primary flow inlet pressure from 2.2 MPa to 3.25 MPa,secondary flow inlet pressure from 0.36 MPa to 0.51 MPa,ejector back pressure from 0.45 MPa to 0.67 *** were drawn from the experimental results,and the experimental data can be used for validation of theoretical model for both critical and subcritical mode.

关键词： ejector performance refrigeration R134a experiment

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fEffect of alkali and alkaline metals on gas formation behavior and kinetics during pyrolysis of pine wood

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Fuel 2021年 290卷

作者： Li, Jinhu Burra, Kiran G. Wang, Zhiwei Liu, Xuan Gupta, Ashwani K. The Combustion Laboratory Department of Mechanical Engineering University of Maryland College ParkMD20742 United States Faculty of Engineering China University of Geosciences WuhanHubei430074 China College of Environmental Engineering Henan University of Technology Zhengzhou450001 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China

This study examines the acid and alkaline treatment of pine wood to help understand the effect of alkali and alkaline earth metals (AAEMs) content on the pyrolysis behavior at different temperatures. Acid and alkali pretreatment of pine wood were conducted to modify AAEMs content by ion-exchanging method. Thermal kinetic behavior of the pretreated samples was first conducted by a thermogravimetric analyzer (TGA) at different heating rates that provided activation energies of pyrolysis. Gas formation behavior of the samples for different extents of conversion was carried out in a fixed-bed reactor at two different temperatures of 823 K and 1073 K. Evolutionary behavior of the gas components during pyrolysis, including flow rate, and yield and their energy content were measured and compared. Results showed that the values of activation energies increased with the extent of conversion for all the pretreated samples examined. The effect of AAEMs on pyrolysis behavior of biomass varied with the extent of conversion. The presence of AAEMs in biomass decreased the decomposition energy at low conversion while it greatly improved under high conversion. Besides, alkali treated sample with higher AAEM content enhanced the gas and char yield while it reduced the bio-oil production at low temperature with low conversion. However, at high temperature the opposite trend was observed. Presence of AAEMs was favorable for the generation of H2, CO, CO2 and CnHm at low temperature, while it showed an inhibition effect on CO and CnHm yield and syngas energy at high temperature. The catalytic mechanism of AAEMs on the pyrolysis behavior at different temperatures was discussed based on activation energy and gaseous formation. Results revealed decomposition of carboxylate at low temperature and formation of stable biomass-Na (BM-Na) structure at high temperature that led to the variation of activation energy and changed gaseous products yield and syngas energy. Acid washing pretreatment wa

关键词： Activation energy

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Control of two-phase flow around a cylinder with a cylindrical attachment: A numerical study

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Ocean engineering 2025年 334卷

作者： Wang, Ziqing Hu, Yu Huang, Shengxian Zhang, Yongxing Moghtaderi, Behdad 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 National Engineering Laboratory for Pipeline Safety/MOE Key Laboratory of Petroleum Engineering/Beijing Key Laboratory of Urban Oil and Gas Distribution Technology China University of Petroleum – Beijing Beijing102249 China Centre for Innovative Energy Technologies The University of Newcastle CallaghanNSW2308 Australia

Mitigating flow separation, vortex shedding and sediment-induced erosion around cylindrical structures is critical for enhancing marine engineering safety. This study investigates the hydrodynamic performance of a two-phase flow around a cylinder equipped with an auxiliary cylinder under realistic ocean conditions. key parameters include the clearance ratio (G/D), particle characteristics (size and concentration), and vibration modes of the auxiliary body. This study investigates real ocean conditions, focusing on the influence of clearance ratio (G/D) and an auxiliary cylinder on flow field changes with varying particle characteristics. The results demonstrate that: (1) A clearance ratio G/D = 0.1 yields the optimal drag reduction (57.18 %) for the primary cylinder in single-phase flow;(2) Larger particles weaken vortex-particle interactions, while higher particle concentrations exacerbate uneven deposition near the cylinder;(3) Transverse vibration of the auxiliary body (amplitude ratio = 0.025, frequency ratio = 0.65) reduces drag by 18.7 % compared to stationary configurations. These findings provide insights into flow control strategies for offshore structures subjected to sediment-laden flows. © 2025 Elsevier Ltd

关键词： Marine safety

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