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The Molecular Dynamics Simulation of Thermal Properties of R290 for Auto-cascade Refrigeration System

Recent Patents on Mechanical engineering 2023年第5期16卷 345-358页

作者： Feng, Haocheng Liu, Zhenzhen Wang, Zilong Zhang, Hua School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

Background: Hydrocarbons are increasingly being considered as potential fourth-generation refrigerants due to their environmentally-friendly properties. However, accurate prediction and calculation of their thermal properties are essential for their industrial application. Objective: In this study, molecular dynamics simulations were performed to calculate the density, self-diffusion coefficient, viscosity and thermal conductivity of R290 at various operating temperatures of 200-240 K and pressures of 0.15 and 0.20 MPa, and 270-390 K and pressures of 1.5 and 2.0 MPa to veri-fy the feasibility of the methods. Methods: The equilibrium molecular dynamics simulation (EMD) approach was utilised. The soundness of the model and force field were verified by calculating the density of the system during the relaxation phase. In the output stage, the self-diffusion coefficient was calculated using the Einstein relation, while the viscosity and thermal conductivity were calculated using the Green-Kubo method. The simulation results were compared with the NIST data values, and the errors were analysed. Results: The density simulation results for R290 in the relaxation phase yielded an overall average absolute relative deviation (AARD) value of 3.97%. In the output stage, the simulation results for the transport coefficients of R290 showed AARD values of 7.68%, 6.60% and 11.04% for the self-diffusion coeffi-cient, viscosity, and thermal conductivity, respectively, compared to the NIST data values. Conclusion: These results indicate the feasibility of using molecular dynamics simulations to study the transport properties of hydrocarbon refrigerants. The findings also provide a foundation for future research on hydrocarbon refrigerant mixtures. Patent: The research presented in this work could serve as a valuable reference for future patent applications and technological innovations related to hydrocarbon refrigerants, particularly R290. This includes, but is not limited to, delive

关键词： Viscosity

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Numerical Stability and Accuracy of Contact Angle Schemes in Pseudopotential Lattice Boltzmann Model for Simulating Static Wetting and Dynamic Wetting

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Computer Modeling in engineering & Sciences 2023年第10期137卷 299-318页

作者： Dongmin Wang Gaoshuai Lin Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering School of Energy and Power EngineeringUniversity of Shanghai for Science and TechnologyShanghai200093China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application Suzhou University of Science and TechnologySuzhou215009China

There are five most widely used contact angle schemes in the pseudopotential lattice Boltzmann(LB)model for simulating the wetting phenomenon:The pseudopotential-based scheme(PB scheme),the improved virtualdensity scheme(IVD scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the fluid layer density above the wall(MPB-C scheme),the modified pseudopotential-based scheme with a ghost fluid layer constructed by using the weighted average density of surrounding fluid nodes(MPB-W scheme)and the geometric formulation scheme(GF scheme).But the numerical stability and accuracy of the schemes for wetting simulation remain unclear in the *** this paper,the numerical stability and accuracy of these schemes are clarified for the first time,by applying the five widely used contact angle schemes to simulate a two-dimensional(2D)sessile droplet on wall and capillary imbibition in a 2D channel as the examples of static wetting and dynamic wetting simulations respectively.(i)It is shown that the simulated contact angles by the GF scheme are consistent at different density ratios for the same prescribed contact angle,but the simulated contact angles by the PB scheme,IVD scheme,MPB-C scheme and MPB-W scheme change with density ratios for the same fluid-solid interaction *** PB scheme is found to be the most unstable scheme for simulating static wetting at increased density ratios.(ii)Although the spurious velocity increases with the increased liquid/vapor density ratio for all the contact angle schemes,the magnitude of the spurious velocity in the PB scheme,IVD scheme and GF scheme are smaller than that in the MPB-C scheme and MPB-W scheme.(iii)The fluid density variation near the wall in the PB scheme is the most significant,and the variation can be diminished in the IVD scheme,MPB-C scheme *** variation totally disappeared in the GF scheme.(iv)For the simulation of capillary imbibition,the MPB-C scheme,MPB-Wschem

关键词： Pseudopotential lattice Boltzmann model contact angle scheme static wetting dynamic wetting capillary imbibition

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Performance comparison investigation on different pulse tube position heat pumps with power recovery displacer

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International Journal of Refrigeration 2025年 176卷 1-16页

作者： Zhu, Shenglin Chen, Xi Zhu, Yifan Qi, Yingxia School of Energy and Power Engineering University of Shanghai for Science and Technology 516 Jungong Road Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology 516 Jungong Road Shanghai200093 China

Spacecraft waste heat is dissipated into space primarily by radiation. To improve the heat dissipation efficiency of spacecraft radiators in high-temperature environments and reduce heat wastage in spaceflight thermal control systems, thermoacoustic heat pumps (TAHP) are considered a viable method for increasing radiator cooling temperatures and recovering waste heat. In this study, one-dimensional simulations are used to optimize the geometrical parameters of the 100-watt work recovery thermoacoustic heat pump (WRTAHP) for various pulse tube positions. The performances of the two systems are compared at a cold-end temperature of 293 K and a hot-end temperature of 353 K. The results reveal that a heating capacity of 256 W with a relative Carnot efficiency of 35.01 % is achieved for the pulse tube front-type thermoacoustic heat pump (FTTAHP), whereas the pulse tube back-type thermoacoustic heat pump (BTTAHP) obtains a heating capacity of 225 W with a relative Carnot efficiency of 30.59 %. As the cold-end temperature decreases, the coefficient of performance is reduced for FTTAHP, while the performance of BTTAHP shows a substantial improvement. At a cold end temperature of 233 K and a hot-cold end temperature difference of 60 K, a heating capacity of 268 W with a relative Carnot efficiency of 50.57 % is achieved for BTTAHP. Furthermore, the heating capacity of the BTTAHP is not significantly increased by adopting the active phase adjustment structure. In summary, the FTTAHP is suitable for spacecraft radiator applications and avoids high temperatures affecting compressor operation, whereas the BTTAHP is better suited for low-temperature heating. © 2025 Elsevier Ltd and IIR

关键词： Waste heat utilization

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Study on Particle Sedimentation in a Cavity Containing Obstacles

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PROCESSES 2025年第4期13卷 980-980页

作者： Yang, Fan Shi, Ren Yan, Zhe Wang, Wencan 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

The sedimentation of particles has a wide range of application scenarios in industry. In this paper, the sedimentation of a single particle in a cavity containing obstacles is simulated using the immersed boundary-lattice Boltzmann method. The computational results show that the presence of obstacles will alter the sedimentation of the particle, and the particle will undergo a change in the direction of rotation during the period when it tumbles over the surface of the obstacle and continues to sedimentation after leaving the obstacle. Increasing the particle-obstacle eccentricity or decreasing the particle-obstacle diameter ratio will shorten the particle-obstacle interaction time. When the sedimentation of a particle passes through the gap between two obstacles, it can be influenced by the far-side obstacle and interact with the near-side obstacle for a second time, and the influence of the far-side obstacle on the sedimentation of the particle disappears when the gap between the two obstacles exceeds a certain threshold. These results quantitatively elucidate the critical role of obstacle configuration in modulating particle dynamics, providing valuable insights for optimizing industrial sedimentation systems and advancing predictive models for multiphase flows in complex geometries.

关键词： particle sedimentation lattice Boltzmann method immersed boundary method

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Numerical study on the effect of rim seal slot filleting on turbine endwall cooling

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AIP ADVANCES 2025年第1期15卷

作者： Li, Xinchun Wei, Na Shi, Liuliu Chen, Eryun 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

In this study, the effect of rim seal slot filleting on turbine endwall film cooling performance is numerically investigated. For comparison with the baseline case, five different fillet radius and width (R/W) ratios are adopted, i.e., R/W = 1.25, 2.5, 3.75, 5, and 6.25. The results indicate that an improvement up to 10% in overall film cooling effectiveness can be achieved with smaller fillet radii. However, this effect diminishes as the fillet radius increases and becomes negative at R/W = 6.25. By examining the contours of the film cooling effectiveness, a prominent inclined strip can be observed across the blade passage. The analysis indicates that the pressure-side leg horseshoe vortex is the primary factor contributing to the variation in the film cooling performance. Furthermore, the film cooling effectiveness can be slightly improved near the suction side of the blade leading edge as the result of the suppression of endwall separation in this region. The rim seal slot filleting eliminates the slot leakage separation, which, in turn, expedites the endwall cooling flow. Eventually, pressure-side leg horseshoe vortex is weakened and the performance of the film cooling is improved. As the fillet radius continues to increase, the through-flow area for the cooling flow enlarges, resulting in a gradual decrease in the film cooling performance. (c) 2025 Author(s).

关键词： Vortex flow

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Numerical Study on the Coupled Impact of Periodic Wake and Pulsating Jet on Film Cooling Efficiency on a Flat Wall

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APPLIED SCIENCES-BASEL 2025年第5期15卷 2558-2558页

作者： Peng, Qiushou Shi, Liuliu 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

This paper presents a numerical study investigating the coupled effects of periodic incoming wake and pulsating jets on the film cooling efficiency of a flat wall. The sweeping frequency of the wake is maintained at a constant 10 Hz, while the blowing ratio (M) varies from 0.3 to 1. By adjusting the initial position of the rod, different phase lags are generated to assess the interaction between the incoming wake and the pulsating jet concerning film cooling efficiency. The results reveal that coupling the wake-affected surface with the low-blowing-ratio phase of the pulsating jet can effectively enhance film cooling efficiency at lower blowing ratios. Conversely, at higher blowing ratios, aligning the low-pressure phase of the pulsating jet at the film hole with the high-blowing-ratio jet pulsation results in an improved film cooling effect. Notably, when the phase lag (psi) is set to zero, the cooling efficiency of the pulsating film reaches its maximum across all blowing ratios, indicating an optimal coupling strategy.

关键词： wake pulsating jet film cooling coupling phase lag

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Simultaneous measurement of particle size distribution and mixing ratio based on Monte Carlo ultrasonic attenuation model

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MEASUREMENT SCIENCE AND TECHNOLOGY 2025年第2期36卷 026014-026014页

作者： Zhang, Shiwei Su, Geyi Niu, Gege Chen, Jingwen Su, Mingxu 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

Mixed particle systems are commonly employed in industrial processes, where the characterization of particle size parameters and mixing ratio can frequently serve as key indicators in process control and production optimization. A Monte Carlo (MC) model was developed to numerically predict and study the ultrasonic attenuation spectrum characteristics in the polymethyl methacrylate (PMMA)-glass aqueous suspension, and together with the particle swarm optimization (PSO) algorithm, to handle the inverse problem in solving the particle size, distribution width, and mixing ratio. The results of the numerical simulations indicate that there exists a linear relationship between the attenuation coefficient and the mixing ratio, with the particle size exerting a significant influence. Furthermore, the multi-parameter simultaneous inversion also yielded calculation deviations of less than 1%, 3%, and 6% for the mixing ratio, characteristic diameter, and distribution width, respectively, in comparison to their given values. Afterward, a series of experiments were conducted to quantify the particle size and mixing ratio through the analysis of ultrasonic spectra. In spherical PMMA-glass aqueous suspensions, the measurement error for the mixing ratio and particle size parameters are found to be less than 7% and 10%, respectively, when compared to the image method and the given values. Nevertheless, the measurement errors are slightly increased in a non-spherical mixed particle system, where the volume median diameter and mixing ratio are still less than 10%. The MC modeling and PSO algorithm offer the potential to characterize particle size and mixing ratio for mixed particle systems in industrial applications.

关键词： Monte Carlo method mixed particle system polydispersity ultrasonic attenuation parameter inversion

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Experimental and numerical simulation study of particles flow in the microchannel equipped with fan-shaped rib on sidewall

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PARTICUOLOGY 2025年 100卷 45-61页

作者： Yang, Zhenyu Li, Xiaolong Zhang, Weifeng Cai, Tianyi Zhou, Wu 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

Microchannels are widely used in electronic device cooling due to their efficient heat dissipation performance, but particle deposition is still a major challenge limiting their performance. To design and optimize efficient microfluidic devices, this paper proposes to introduce fan-shaped ribs within the microchannels to reduce particle deposition. The placement of fan ribs of different heights in the microchannel was first experimentally determined, and then the particle motion characteristics were further investigated by numerical simulations. The results show that the fan-shaped ribs can effectively reduce particle deposition and exhibit greater deposition inhibition with increasing rib height. The channel constriction induced by the rib structure promotes the radial diffusion of particles in the downstream, and at the same time significantly enhances the radial component of the particle flow, which is improved by 5.76 %, 7.98 %, and 10.86 %, respectively. In addition, recursive analysis revealed that the incorporation of fan-shaped ribs shifted the particle flow from a homogeneous, periodic mode to a more abrupt diffusion mode, which contributed to the improvement of particle dispersion. This study provides a new strategy without the use of surfactants, which provides a reference for the optimized design of microchannel cooling systems. (c) 2025 Chinese Society of Particuology and Institute of Process engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI

关键词： Microchannel Fan-shaped rib Particle flow pattern Recursive analysis

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Balanced deep learning-based bubble segmentation: Model comparison, optimization, and application in microbubble detection

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flow MEASUREMENT AND INSTRUMENTATION 2025年 104卷

作者： Cai, Tianyi Tang, Ao Xu, Rixin Zhou, Jiawen Gong, Wenchao Zhou, Wu 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

The accurate segmentation and analysis of bubbles are crucial for understanding bubble generation mechanisms and improving industrial microbubble detection. This study aims to evaluate and optimize deep learning-based bubble segmentation models. Firstly, a systematic model evaluation matrix is proposed, including the general model performance, defocused bubble size prediction accuracy, and overlapping bubble segmentation. Secondly, four models, including SplineDist, StarDist, YOLOv8-seg, and Mask R-CNN, are compared. The SplineDist-M16 model demonstrates superior image processing speed (7.84 FPS) and high accuracy in bubble size prediction with minimal misdetection (6.1 %). Compared to other models, SplineDist-M16 excels in edge fitting and overlapping bubble identification. The optimized model provides rapid, accurate measurement of bubble quantity, size, and shape, offering insights into bubble formation and guiding microbubble generator design. This study paves the way for real-time microbubble detection in industrial applications and suggests further model improvements through simulated data training and enhanced overlapping bubble segmentation. Furthermore, the SplineDist-M16 model was utilized to analyse the impact of flow rate and backpressure on microbubble characteristics generated by a Venturi-tube microbubble generator. The results show that increased flow rate reduces bubble size and increases bubble circularity, while backpressure has minimal impact on bubble size distribution and shape.

关键词： Microbubbles Shadowgraphy Image segmentation Defocused bubbles Overlapping bubbles U -net

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Two-phase flow characteristics and leakage in the shaft seal of steam screw expanders

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INTERNATIONAL JOURNAL OF REFRIGERATION 2025年 172卷 214-227页

作者： Tian, Yafen Wang, Zebin Liu, Zhixiang Jiang, Ziqi Zhao, Zhaorui 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

Twin-screw expander is an efficient technology for steam pipeline pressure recovery applications. It operates at lower pressures than turbines and exhibits good performance with droplets. Leakage through the suction end face directly reduces the expander's volumetric efficiency, highlighting the significance of research on shaft seals. This study confirms that the Wet Steam Model is more accurate than the Ideal and Real Gas Models in reflecting the phase change phenomena and flow characteristics of steam after throttling. The effects of four key operating parameters were further investigated on the leakage and flow characteristics of the shaft seal, including suction pressure, superheat degree, rotating speed and liquid mass fraction. The results indicate that, within the specified pressure range, droplet condensation occurs after the final throttling when the superheat ranges from 0 to 30 K. Furthermore, leakage decreases by 1.5 % to 1.7 % with every increment of 10 K in superheat. Higher rotating speeds alter the steam flow path due to wall drag, thereby reducing leakage. An optimal liquid mass fraction of 0.1 was found for two-phase operating conditions, resulting in a 3.6 % reduction in leakage and a 20 K decrease in outlet temperature.

关键词： Steam expander Two-phase flow Labyrinth seal Leakage simulation

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