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Transient Cooling Performance of R134a Flash-Evaporation Spray Enhanced by Cold Air Jet: A Novel Heat Transfer Enhancement Method in Laser Dermatology

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SSRN 2022年

作者： Li, Bufa Wang, Junfeng Tian, Jiameng Chen, Bin Xu, Haojie School of Energy and Power Engineering Jiangsu University Zhenjiang212013 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

Nevus of Ota is a dermal hyperplastic pigmented disease with a morbidity rate of 0.1%–0.6% in the Asian population. Laser surgery with the assistance of cryogen spray cooling (CSC) is a potential clinical treatment for nevus of Ota. However, for Asians with high melanin content, it is necessary to enhance cooling capability without the increment of refrigerant amount. In this study, a R134a flash-evaporation cryogen spray cooling coupled with cold air jet (CSC-CAJ) was developed to improve the cooling capacity. Epoxy resin was employed as a skin phantom to investigate the heat transfer characteristics of CSC-CAJ with different air jet parameters. Air jet parameters of CSC-CAJ are recommended to be T a = -7 °C, V a = 3 m 3 /h Z a = 10 mm and Φ a = 30°. Compared to CSC, CSC-CAJ could reduce the minimum surface temperature from -39 °C to -42.1 °C, and the average value of convection heat transfer coefficient ( h ) of CSC-CAJ could increase from 8 W/(m 2 ·k) to 12.9 W/(m 2 ·k) or 61.3% for the recommended parameters. The liquid film residence time ( τ ) decreases from 301 ms to 234 ms or 23.3%. In addition, based on the visualization observation and surface heat transfer measurement, the frost formation phenomenon on the surface and the heat transfer enhancement mechanisms are well understood. Four modes, including Leidonfrost mode, no runoff mode, runoff mode and evaporation mode, are proposed to describe the four stages of CSC-CAJ. A non-dimensional correlation of normalized Nusselt number ( Nu *) and time ( t *) is summarized. The primary heat transfer enhancement mechanism of CSC-CAJ is found to be the increase in cryogen evaporation rate and the ratio of heat removal from the phantom surface to phase change latent heat. © 2022, The Authors. All rights reserved.

关键词： Evaporation

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Numerical simulation of condensation of supercritical water gasification products in a supersonic nozzle

International Journal of Fluid Engineering

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International Journal of Fluid engineering 2024年第4期1卷 76-88页

作者： Hongtu Wu Miso Jurcevic Henrik Ström Muhammad Shahzad Khurram Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong University28 Xianning West RoadXi’an 710049ShaanxiChina LTEF—Laboratory for Thermodynamics and Energy Efficiency Faculty of Electrical EngineeringMechanical Engineering and Naval Architecture(FESB)University of SplitRudjera Boskovica 3221000 SplitCroatia Chalmers University of Technology GöteborgSweden COMSATS LahorePakistan

The clean and efficient separation of supercritical water gasification products(SCWGP)has emerged as a significant challenge in supercritical water gasification *** paper proposes the use of a supersonic nozzle for the condensation and separation of H2and CO_(2)from SCWGP,leveraging the high-pressure characteristics of these *** establishing a flow model and a condensation model for the supersonic nozzle,the effects of inlet pressure and inlet temperature on the condensation process are *** analysis reveals that the latent heat released during condensation causes an abnormal distribution of pressure and temperature within the *** the inlet pressure of the nozzle is increased from 7.0 to 9.0 MPa,the liquid phase mass fraction at the outlet rises from 5.3×10^(-3)to ***,when the inlet temperature is lowered from 300.0 to 290.0 K,the liquid phase mass fraction at the outlet also rises from 5.3×10^(-3)to *** increase in inlet pressure leads to the condensation location shifting toward the throat by~8.5×10^(-3)m·MPa^(-1),while the impact of inlet temperature is approximately-2.3×10^(-3)m·K^(-1).The nucleation rate in the nozzle is always concentrated in a small region.

关键词： condensation separation outlet

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Experimental Study on Stable Jet Impact Process Under Simulated Pipeline Rupture

Experimental Study on Stable Jet Impact Process Under Simula...

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Student Conference on Research and Development (SCOReD)

作者： Zhang Tao Bi Qincheng Zhao Jinle Wang Teng Chen Jingrong Feng Fan State Key Lab Multiphase Flow Power Engn Xi’an Jiaotong University Xi’an Shaanxi China School of Energy Power and Mechanical Engineering North China Electric Power University Bao’ding Hebei China

ISBN: (数字)9798350318821

ISBN: (纸本)9798350318838

In this study, an advanced experimental system was utilized that incorporated heating, jetting, recycling, and cooling capabilities to ensure the successful execution of stable jet impact experiment that simulating a pipeline complete rupture. High-temperature resistant tempered glass was employed in the experimental system to realize the visibility. During the experiment, 8mm pipes/nozzles of varying lengths were employed as the test sections, and jetting phenomena when the import status is single-phase cold water or two-phase mixture at 0-2MPa were obtained by high-resolution photos. Additionally, the shape of the jet cone and the impact force exerted on the target plate were meticulously analyzed after the working fluid under different state parameters jetting into an atmospheric pressure environment through pipes/nozzles. The research also focused on the variation trend in the magnitude of the jet-impact force, as a function of inlet pressure and temperature, target plate distances, and length-to-diameter ratios. The research findings revealed that cold water(below 100°C), sub-cooled water(above 100°C but not reaching saturation temperature), and two-phase steam-water mixture exhibited distinct jet cone shapes during the jetting process, resulting in varying distributions of the jet force. Furthermore, the distance from the spout to the target plate and the length-to-diameter ratio significantly influenced the magnitude of the jet impact force.

关键词： Resistance Visualization Temperature distribution Fluids Shape Force Pipelines

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Hierarchical Heterojunctions of Metal Sulfide Nanosheets/ Metal Oxide Nanofibers for an Efficient Detection of Formaldehyde

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SSRN 2024年

作者： Zhu, Lei Zhang, Jiaxin Wang, Jianan Liu, Jianwei Wang, Ze Yan, Wei Xi’an Key Laboratory of Solid Waste Resource Regeneration and Recycling State Key Laboratory of Multiphase Flow Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China School of Physics and Electrical Engineering Weinan Normal University Chaoyang Street Weinan714099 China School of Chemistry and Chemical Engineering Xi’an University of Science & Technology Xi’an710054 China

The construction of transition metal dichalcogenides (TMDs) heterojunctions for high performance gas sensors has garnered significant attention due to their capacity to operate at low temperature. Herein, we realize two-dimensional (2D) WS2 nanosheets in situ grown on one-dimensional (1D) In2O3 nanofibers to form heterostructures for formaldehyde (HCHO) gas sensors. Capitalizing on the p-n heterojunctions formed between WS2 and In2O3, coupled with the high surface-to-volume ratio characteristic of 1D nanostructures, the WS2/In2O3 NFs sensor demonstrated a high gas response value of 12.6 toward 100 ppm HCHO at operating temperature of 140 ℃, two times greater than that of the pristine In2O3 sensor. Meanwhile, the sensor presents remarkable repeatability, rapid response/ recovery time, and good long-term stability. The superior sensing capabilities of WS2/In2O3 NFs heterojunction are attributed to the combined impact of the increased charge transfer and the presence of more sites for gas adsorption. The research endows a potent approach for fabricating TMDs heterojunctions to significantly improve the performance of gas sensors. © 2024, The Authors. All rights reserved.

关键词： Tungsten compounds

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Interfacial Mass Transfer Enhancement for Photoelectrochemical Water Splitting Using 3d flow Field Structure

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SSRN 2022年

作者： Wang, Baoyuan Yang, Suyi Lai, Yongquan Su, Jinzhan International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

Hydrogen production using solar energy water splitting is an economical and feasible clean energy solution. It is recognized that the efficiency of photoelectrochemical water splitting is not only related to the electrode material, but also influenced by the mass transport at the electrode surface. To investigate that relationship, we design a novel photoelectrochemical water splitting reactor, which generates a turbulent flow at the electrode/electrolyte interface, and change the temperature of the electrolyte. It was found that the flow rate and temperature of the electrolyte mainly affect the mass transport and charge transfer at the photoelectrode/electrolyte interface. Based on the results of LSV, EIS, and the calculation of mass transfer coefficient, the photoelectrochemical performance of the system at flow rate ranging from 0 to 145 ml/min and temperature between 20-90 °C is analyzed. The influence of the flow rate on the photocurrent density is more significant during the transition of the flow state and at the high flow rate. The best performance is achieved at the flow rate of 127 ml/min, and the temperature of 90 °C. The electrochemical impedance spectroscopy results show that in the test range, ion transport impedance decreases with increasing electrolyte temperature, as a result, the photocurrent density at 90 °C is increased about 2.2 times compared to that at 20 °C. It is also shown that the design of the 3D step-like structure has a more significant effect on the electrolyte flow than the planar structure, and the photocurrent density is increased about 1.3 times. © 2022, The Authors. All rights reserved.

关键词： Mass transfer

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Gold/oxide heterostructured nanoparticles for enhanced SERS sensitivity and reproducibility

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Rare Metals 2020年第7期39卷 834-840页

作者： Qi-Kui Fan Ting-Zhuo Liu Hou-Shen Li Shu-Meng Zhang Kai Liu Chuan-Bo Gao Frontier Institute of Science and Technology and State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710054China College of Chemistry and Material Science Shandong Agricultural UniversityTaian 271018China

In surface-enhanced Raman scattering(SERS),it is highly desirable to obtain Raman signals with high sensitivity and reproducibility from noble metal nanoparticle substrates,which remains a great challenge due to the inhomogeneity of the plasmonic coupling that is sensitive to the interparticle *** this work,we report that the interparticle plasmonic coupling could be circumvented by first synthesizing Au/metal or nonmetal oxide heterostructured nanoparticles and then depositing them uniformly onto the substrates,leading to high reproducibility of the Raman *** plasmonic coupling has been found at the Au/oxide interface,which enables high sensitivity of the SERS analysis that accompanies the excellent signal *** different oxides investigated(SiO2,TiO2 and Fe2O3),the Au/Fe2O3 heterostructured nanoparticles demonstrate the highest Raman enhancement *** believe our strategy opens a promising route to fabricate SERS substrates that are capable of sensitively and quantitatively detecting molecules of interest in a much reliable manner.

关键词： Gold nanoparticles Au/oxide heterostructures Hot spots Surface-enhanced Raman scattering Reproducibility

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Research on the Combustion Effect and Mechanism of Aluminum Droplets in Ap/Htpb Composite Propellant

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SSRN 2023年

作者： Yang, Bin Wang, Jiahao Lou, Yongchun Zhao, Yu Wang, Ji Wang, Ying Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Space Propulsion Technology Research Institute Shanghai201109 China

To investigate the combustion phenomenon of aluminum droplets within propellants, this study amalgamates the evaporation combustion process of aluminum droplets with the AP/HTPB (Ammonium perchlorate/Hydroxyl-terminated polybutadiene) multi-flame structure model. Consequently, a numerical simulation approach is established to depict the combustion behavior of aluminum droplets in a high-temperature gas environment. The paper scrutinizes the dynamics, deformations, combustion characteristics, and their influence on the propellant flow field under diverse conditions. The findings of this research affirm that the non-uniform flow velocity at the AP and HTPB inlets imparts distinct pressures on the droplets' surface, thereby precluding their spherical morphology. As the droplet diameter diminishes, the effect of deformation gradually abates, leading the droplets to gravitate towards the AP region. The addition of aluminum droplets disrupts and enhances heat transfer within the external flow field of propellant combustion, while their own combustion engenders a substantial amount of heat, thus elevating the overall combustion temperature of the propellant. Moreover, aluminum droplets perturb the distribution of different components in the flow field, affording more opportunities for intermolecular encounters, and consequently augmenting the efficiency of the overall reaction compared to scenarios without aluminum droplets. Remarkably, the combustion efficiency of aluminum droplets is amplified in high-pressure environments. © 2023, The Authors. All rights reserved.

关键词： flow fields

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General analytical equation of state for nanoconfined gases derived from statistical physics

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Physical Review E 2025年第2期111卷 025413-025413页

作者： Chengzhen Sun Haoxuan Li Zhixiang Zhao Mehdi Neek-Amal Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China School of Urban Planning and Municipal Engineering Xi'an Polytechnic University Xi'an Shaanxi 710048 China Department of Physics Faculty of Sciences Shahid Rajaee Teacher Training University 16875-163 Lavizan Tehran Islamic Republic of Iran Department of Physics University of Antwerp Groenenborgerlaan 171 2020 Antwerp Belgium

The pressure prediction of nanoconfined gases is crucial for various industrial applications, yet existing equations of state (EOS) often compromise between accuracy and usability. This study derives a theoretical EOS in analytical form, combining precision and practicality through statistical physics. It begins by examining the pressure drop mechanism due to adsorbed molecules and refines molecular pairing and potential energy interactions. The resulting EOS accurately predicts the pressure of gases in nanoconfined spaces, especially with an average prediction error of about 5% for strongly adsorbing gases like nitrogen, oxygen, and argon. Additionally, it aligns with the Van der Waals EOS under macroscopic conditions, offering a unified framework across scales. This model enhances both engineering applications and the understanding of nanoconfined EOS.

关键词： Van der Waals forces

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Occurrence and flow Characteristics of Methane in High-Temperature and High-Pressure Nanopores of Deep Shale

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2025年第4期46卷 1200-1204页

作者： Wang, Rui Sun, Chengzhen Yang, Xu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Petroleum Engineering School Southwest Petroleum University Chengdu610500 China

The understanding of gas transport in deep shale nanopores is still not clear. In this study, molecular simulations of methane occurrence and flow in illite slits of deep shales under the condition of high-temperature and high-pressure was carried out. The occurrence, diffusion and flow characteristics of methane molecules were analyzed. The effects of temperature and pressure on methane occurrence and flow were elucidated. The results show that the distribution of methane density in illite slits is nonuniform, and there are density peaks near the wall. Compared with Middle and Shallow shales, more methane molecules can exist in the pores of deep shale, and the diffusion ability is limited. The methane flow flux decreases with the decrease of pressure (5∼80 MPa) and increases with the decrease of temperature (60∼120◦C). Pressure is the main dominating factor of flow flux, and the flow flux decreases gradually during depressurization. © 2025 Science Press. All rights reserved.

关键词： Nanopores

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Evaluation of droplet drag force model on spray and atomization behaviours of R134a flashing spray 14

Evaluation of droplet drag force model on spray and atomizat...

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14th International Conference on Liquid Atomization and Spray Systems, ICLASS 2018

作者： Zhou, Zhi-Fu Lu, Guan-Yu Zhang, Lu Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Flashing spray is of great importance in a variety of engineering fields, which occurs as the pressurized liquid is released into a low-pressure environment below its saturation pressure. This paper conducts a systematically numerical study on the spray and thermal characteristics of R134a flashing spray with high volatility and low saturation temperature, using a modified sprayFoam solver in the open source tool OpenFOAM-2.4.0. key physics involved in the complex process, including droplet flash boiling, evaporation, droplet transport, breakup, heat transfer and interaction between droplet and gas phases are taken into consideration. The emphasis is put on the droplet drag force model and nozzle diameter on flashing spray including spray morphology, droplet diameter, velocity and temperature. The result indicates that most of the drag force models have little effect on droplet diameter, velocity and temperature distributions in flashing spray, except the Khan-Richardson (K-R) model. The K-R model predicts lower temperature, higher velocity and larger size of droplet, compared to other models. The nozzle diameter greatly affects R134a spray morphology and tip penetration, that smaller diameter contributes to a larger radial expansion at the near nozzle region while leading to a much smaller penetration distance. This research give a useful guidance that how people choose the appropriate drag force model for simulation of flashing spray. © 2018 Solar Turbines Incorporated.

关键词： Morphology

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