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Performance Study of Portable Semiconductor Refrigeration Device Based on CFD simulation

MICROMACHINES 2023年第2期14卷 296-296页

作者： Li, Bin Wang, Feng Jiang, Feng Zhao, Shaocong Wei, Shutao Peng, Piaolin Wang, Xiangdong Jiang, Anna Huaqiao Univ Inst Mfg Engn Xiamen 361021 Peoples R China Liming Vocat Univ Coll New Mat & Footwear Engn Quanzhou 362000 Peoples R China Xiamen Univ Technol PE Dept Xiamen 361000 Peoples R China Innovat & Res Ctr 361 CHINA Co Ltd Xiamen 361000 Peoples R China Jimei Univ Sch Phys Educ Xiamen 361021 Peoples R China Huaqiao Univ Coll Mech Engn & Automation Xiamen 361021 Peoples R China

Since the summer of 2022, the whole world has suffered the abnormal weather phenomena of high ambient temperature. Equipment for refrigeration, particularly portable refrigeration equipment, is crucial for personal protection in high-temperature environments, but cooling performance and miniaturization have been challenging issues. A portable air conditioner based on a semiconductor refrigeration device for human body cooling was developed. The total weight of the device is 450 g. The overall power consumption of the device is 82 W and the energy consumption ratio of semiconductor cooling plate is 0.85. The semiconductor refrigeration technology is based on the Peltier effect, supplemented by a DC fan to send the cooling air out to a specified position or zone. The structural parts are manufactured by 3D printing technology to make the overall size of the device more compact. The air volume and cooling performance of the device were analyzed by computational fluid dynamics simulation and the temperature distribution was measured by an infrared thermal imager and other instruments, and the measured results agreed with the CFD simulation results. The test ambient temperature was 20 degrees C. The measurement results showed that the wind speed of the hot air outlet was 6.92 m/s and that of the cold air outlet was 8.24 m/s. The cold air surface temperature reached a stable state of 13.9 degrees C in about 4 min, while the hot air surface temperature reached a stable state of 47.2 degrees C.

关键词： computational fluid dynamics simulation portable cooling device semiconductor refrigeration technology

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The impact of semi-open street roofs on urban pollutant exposure and pedestrian-level thermal comfort in 2-D street canyons

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BUILDING AND ENVIRONMENT 2023年 239卷

作者： Zhong, Huiru Feng, Jiaxi Lam, Cho Kwong Charlie Hang, Jian Hua, Jiajia Gu, Zhongli Sun Yat Sen Univ Sch Atmospher Sci Southern Marine Sci & Engn Guangdong Lab Zhuhai Zhuhai Peoples R China Sun Yat Sen Univ Key Lab Trop Atmosphere Ocean Syst Minist Educ Zhuhai 519000 Peoples R China China Meteorol Adm Xiongan Atmospher Boundary Laye Beijing Xiongan Peoples R China Guangdong Fans Tech Agro Co Ltd Yunfu Peoples R China

Semi-open street roofs(SOSRs) have been confirmed to provide solar shading for pedestrians, usually improving outdoor thermal comfort but weakening urban ventilation in three-dimensional(3-D) urban districts. However, these positive and negative impacts have rarely been quantified together. Particularly, their impacts in two-dimensional(2-D) street canyons have not been investigated. Accordingly, by conducting computational fluid dynamic(CFD) simulations coupling turbulence and radiation processes, this study investigates the integrated influences of SOSRs on both ventilation/pollutant exposure risks and pedestrian-level outdoor thermal comfort in 2-D full-scale street canyons(aspect ratios AR = H/W = 1, 3, 5;W = 24 m). Isothermal and non-isothermal cases with three solar angles(LST0900, LST1200, LST1500) are considered. The pedestrian-level maximum normalized velocity(Vpedmax/Vinlet) and physiological equivalent temperature(PET) are analyzed for ventilation and thermal comfort assessment. SOSRs have an overall negative impact on present 2-D streets. Without SOSRs, only one main clockwise vortex exists when H/W = 1 and H/W = 3. Compared to the isothermal cases, LST0900 and LST1200 always strengthen this main vortex, while LST1500 weakens it slightly. The SOSRs may produce some secondary near-ground clockwise and counter-clockwise vortexes, which significantly reduce Vpedmax/Vinlet, i.e. from 0.33-0.44 to below 0.07 when H/W = 1 and 0.063-0.13 to 0.049 when H/W = 3. They also increase pedestrian-level PET by 0.9-10.4 degrees C(H/W = 1) and 0.1-4 degrees C(H/W = 3). When H/W = 5, two main vortexes appear in the isothermal case inducing much smaller Vpedmax/Vinlet of 0.004 and solar radiation significantly raises the Vped/Vinlet to 3-25 times without SOSRs. The impacts of SOSRs are not as significant as those at H/W =1 and 3. Overall, the SOSRs impact should be assessed before their application, especially in 2-D streets.

关键词： computational fluid dynamics simulation (CFD) Outdoor thermal comfort Pollutant exposure Two-dimensional (2-D) street canyon Urban microclimate Semi -open street roofs (SOSRs)

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Parameter-Conditioned Sequential Generative Modeling of fluid Flows

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AIAA JOURNAL 2021年第3期59卷 825-841页

作者： Morton, Jeremy Kochenderfer, Mykel J. Witherden, Freddie D. Stanford Univ Dept Aeronaut & Astronaut 496 Lomita Mall Stanford CA 94305 USA Texas A&M Univ Dept Ocean Engn 727 Ross Street College Stn TX 77843 USA

The computational cost associated with simulating fluid flows can make it infeasible to run many simulations across multiple flow conditions. Building upon concepts from generative modeling, we introduce a new method for learning neural network models capable of performing efficient parameterized simulations of fluid flows. Evaluated on their ability to simulate both two-dimensional and three-dimensional fluid flows, trained models are shown to capture local and global properties of the flowfields at a wide array of flow conditions. Furthermore, flow simulations generated by the trained models are shown to be orders of magnitude faster than the corresponding computational fluid dynamics simulations.

关键词： Generative Adversarial Network Two Dimensional Flow computational fluid dynamics simulation Vortex Induced Vibrations Freestream Velocity Flow Visualization Lift Coefficient fluid Flow Power Spectral Density Surrogate Model

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simulation of Binder Infiltration in Additive Manufacturing of Sand Molds

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ADVANCED ENGINEERING MATERIALS 2023年第20期25卷

作者： Erhard, Patricia Tanjavooru, Vivek Teja Hartmann, Christoph van den Bosch, Lucas Seidel, Alexander Volk, Wolfram Guenther, Daniel Fraunhofer Inst Casting Composite & Proc Technol I Lichtenbergstr 15 D-85748 Garching Germany Tech Univ Munich TUM TUM Sch Engn & Design Boltzmannstr 15 D-85748 Garching Germany

This article proposes a computational fluid dynamics approach to simulate binder infiltration in 3D printing of sand molds using OpenFOAM facilitating the identification of suitable levers for application-specific material and process developments. A method for randomly generating powder bulks of designated powder size distributions (PSD) and procedures for automated analysis of the infiltration profile and volume are introduced. simulation is utilized to investigate binder infiltration using different droplet spacings, representing different printheads' resolutions. The apparent particle size at the exact location of the droplets' impact, the droplets' landing position in relation to the respective surface topography, and thus the statistical appearance of particle formations appear to be influencing the infiltration profile. High-speed camera observations show the plausibility of the predicted infiltration kinetics. An exemplary use case compares the predicted infiltration profiles to the compressive strength of specimens printed from silica sand with low binder contents. simulation predicts an average infiltration of 250 mu m that presumably achieves reliable bonding for layer thicknesses up to 365 mu m. A decrease in strength with increasing layer thickness at constant binder contents can be found in the experiment - at layer thicknesses above 350 mu m, only minor strengths are achieved.

关键词： additive manufacturing binder infiltration binder jetting computational fluid dynamics simulation sand molds 3D printing

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Shape Optimization of Pin-Fins by Free-Form Deformation and Active Learning Surrogate Model

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2023年第2期37卷 448-456页

作者： Yang, Fan Chen, Zhaolin Nanjing Univ Aeronaut & Astronaut Nanjing 210016 Peoples R China

The shapes of pin-fins play an essential role in enhancing overall and local forced convective heat removal. This study presents a new design optimization scheme based on the free shape deformation method, which gives rise to nonuniform pin-fin shapes depending on local flow structures interacting with each local pin-fin. The grid of pin-fins is embedded in a parameter space formed by basic function and control points. By moving the position of the control points, the shapes of the pin-fins and the neighborhood grid are deformed during optimization. The optimization objective function is the heat transfer coefficient of the pin-fin arrays at a limited pressure drop to ensure cycle efficiency. In addition, to reduce the computational resources, the active learning surrogate model for constraint global optimization is adopted, which is combined with computationally expensive computational fluid dynamics simulations. To exemplify the effectiveness of the proposed method on optimizing the pin-fin shape, two-dimensional pin-fins in inline arrangements are considered. Finally, an improvement in the heat transfer of 33.4% is achieved as compared to the baseline. Therefore, the proposed method of pin-fin optimization is effective in improving thermal performance.

关键词： Numerical Modeling Heat Transfer Coefficients computational fluid dynamics simulation Thermal Performance Heat Sinks Shape Optimization Sensitivity Analysis Finite Volume Method Multi Objective Genetic Algorithm Probability Density Functions

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Bayesian Gappy Proper Orthogonal Decomposition for Aerodynamic Data Fusion

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AIAA JOURNAL 2023年第9期61卷 4032-4044页

作者： Bertram, Anna Bekemeyer, Philipp Held, Matthias German Aerosp Ctr DLR Inst Aerodynam & Flow Technol D-38108 Braunschweig Germany Airbus Operat GmbH Aerodynam Modelling Loads Aircraft Aerodynam D-28199 Bremen Germany

During the development of an aircraft, a multitude of aerodynamic data are required for different flight conditions throughout the flight envelope. Nowadays, a large portion of these data are routinely acquired by computational fluid dynamics simulations. However, due to modeling and convergence issues especially for extreme flight conditions, numerical data cannot be reliably generated for the entire flight envelope yet. Hence, numerical data are complemented by data from wind tunnel experiments and flight testing. However, the data from these different sources will always show some discrepancies to deal with. Data fusion methods aim at combining the individual strengths and weaknesses of data from different sources in order to provide a consistent data set for the entire parameter domain. In this work we propose an extension to the well-established Gappy proper orthogonal decomposition technique by reformulating the least-squares problem as a regression task. A Bayesian perspective is imposed to account for uncertainties during the data fusion process. This involves a kernelized regression formulation that also addresses the problem of linearity imposed by the dimensionality reduction method and therefore adds more flexibility to the approach. The performance and robustness of the approach is demonstrated investigating an industrially relevant, large-scale aircraft test case fusing high-quality experimental and numerical data. Compared to the established Gappy POD approach, the new method shows a significantly improved agreement with the observed wind tunnel data for the investigated test case. In addition, the new approach enables to provide credible bounds for the fused result, which serve as an indicator for the associated uncertainty.

关键词： Aerodynamic Characteristics computational fluid dynamics simulation European Transonic Windtunnel Data Analysis Gaussian Process Regression Pressure Coefficient Data Fusion Surrogate Model Bayesian Approach

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Temperature Rise on Liner Surfaces of Fuel Cell Electric Vehicle Tanks during Fueling Process

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ENERGY TECHNOLOGY 2023年第9期11卷

作者： Kuroki, Taichi Kreutzer, Cory Leighton, Daniel Martin, Joshua Mohr, Jeffrey Peters, Michael Ruple, Matthew Shaun, Onorato Mathison, Steven Natl Renewable Energy Lab Energy Convers & Storage Syst Ctr Golden CO 80401 USA

Herein, the temperature of the inner tank walls, or plastic liners, of composite pressure tanks in fuel cell electric vehicles during fueling using three-dimensional computational fluid dynamics (CFD) models is evaluated. The liner materials are limited to 85.0 & DEG;C to prevent thermal stress causing material failure that would result in a hydrogen leak. Therefore, the temperature of hydrogen gas must be limited to below 85.0 & DEG;C during the fueling process as dictated by the current fueling protocol. However, there are limited experimental or simulation data confirming that the temperature changes do not exceed the threshold. Herein, the liner temperatures with CFD tank models for two sizes of type IV tanks representative of the upper and lower system bounds that are close to the SAE J2601 fueling protocol (36.0 and 244.0 L) are evaluated. First, each model's reliability is validated with experimental data and then analyzed, and the data are used to evaluate the maximum hydrogen and liner temperatures under real-world fueling conditions. The evaluation shows that the maximum liner surface temperature of each tank model is at least 7 & DEG;C lower than that of the hydrogen. Additionally, there is at least 12 & DEG;C difference found between the upper limit and actual liner temperatures.

关键词： computational fluid dynamics simulation hydrogen fueling process hydrogen temperature plastic liner temperature thermal and flow fields

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Aerodynamic Characteristics of Morphing Supersonic Cascade Under Low-Upstream-Mach-Number Condition

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AIAA JOURNAL 2023年第4期61卷 1708-1719页

作者： Li, Chenzhang Pan, Tianyu Yan, Zhaoqi Zheng, Mengzong Li, Qiushi Dowell, Earl H. Beihang Univ Sch Energy & Power Engn Beijing 100083 Peoples R China Beihang Univ Res Inst Aeroengine Beijing 100083 Peoples R China Duke Univ Dept Mech Engn & Mat Sci Durham NC 27708 USA Aero Engine Acad China Adv Jet Prop Creat Ctr Beijing 101300 Peoples R China Xihua Univ Key Lab Fluid & Power Machinery Minist Educ Chengdu 610039 Peoples R China

For fans of a variable-cycle engine, a good aerodynamic performance over a wide range of rotating speeds is essential. However, when supersonic cascades designed for a high upstream Mach number operate under a low upstream Mach number, a starting problem may occur, which significantly decreases the aerodynamic performance of fan blades. As a result, the operating range of the supersonic cascades is severely limited. To solve the starting problem caused by the mismatch between geometry of supersonic cascades and upstream Mach number, a morphing supersonic cascade is developed. Thus, this study mainly focuses on the effect of the static deformation of supersonic cascades driven by smart materials on aerodynamic characteristics under a low upstream Mach number. To investigate this issue, numerous simulations are conducted on an S-type cascade by finite element method and computational fluid dynamics. As demonstrated by flow structure analysis, the morphing cascades are started under certain morphing configurations while the original cascade operates at nonstarted state. The results show that the deformation driven by smart materials alters the shock wave structures under a low upstream Mach number by adjusting key cascade geometric parameters. Specifically, the morphing cascades achieve 80% reduction of detached shock loss compared with the original cascades.

关键词： Detached Shock Smart Structures and Materials Aerodynamic Performance Finite Element Method computational fluid dynamics simulation Turbomachinery Supersonic Flow Off-design State Morphing Cascade

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Performance enhancement for membrane distillation by introducing insoluble particle fillers in the feed

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DESALINATION 2023年 558卷

作者： Zhang, Yaoling Sun, Jiaqi Guo, Fei Dalian Univ Technol Sch Energy & Power Engn 2 Linggong Rd Dalian 116024 Peoples R China

Temperature and concentration polarizations are typical near-surface phenomena that limit the performance of membrane distillation. An effective method for enhancing the performance of membrane distillation is to me-chanically disturb or break the polarization effect near the membrane surface. In this study, we focused on disturbing the flow boundary layer formed near the membrane surface to eliminate the influence of temperature and concentration polarizations on the membrane distillation performance by introducing insoluble particles as fillers into the feed. It is believed that the sliding/scrolling of insoluble particle fillers on the membrane surface is a practical approach for breaking the boundary layer on the membrane surface and eliminating near-surface polarization. The effects of breaking the near-surface polarization on the membrane distillation performance were systematically investigated via experiments under various conditions and verified with related computa-tional fluid dynamics simulations. The test results demonstrated that the permeate flux, temperature polarization coefficient, and system efficiency of membrane distillation can all be improved with particle fillers. The permeate flux does not increase indefinitely with the rise of particle filler mass flow rate. Moreover, the incorporation of particle fillers is especially effective in enhancing the permeate flux at low feed concentration.

关键词： Membrane distillation Temperature polarization Concentration polarization Particle fillers in the feed computational fluid dynamics simulation

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Micro-milling tool mark removal mechanism by fluid jet polishing and its application for the precision manufacturing of micro-fluidic chip molds

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TRIBOLOGY INTERNATIONAL 2023年 189卷

作者： Zhang, Zili Wang, Chunjin Guo, Jiang Cheung, Chi Fai Hong Kong Polytech Univ Dept Ind & Syst Engn State Key Lab Ultraprecis Machining Technol Hung HomKowloon Hong Kong Peoples R China Dalian Univ Technol State Key Lab High Performance Precis Mfg Dalian Peoples R China

The surface quality of micro-channels has a significant impact on their functional performance. Ultra-precision polishing of the micro-channel (mold) is essential to meet the requirements of the equipment. The tool marks resulting from the former manufacturing procedure such as micro-milling should be removed in the polishing process. fluid jet polishing (FJP) is a promising method to achieve high surface quality as well as superior applicability to the small structure unit. However, the effect of the initial surface morphology and polishing parameters on the tool marks removal capacity in FJP is not clear. The manufacturing parameters are determined by trial and error approach, which is time-consuming and costly. In this paper, the tool mark removal capability of FJP was investigated theoretically and experimentally considering the effect of tool mark interval and abrasive size. computational fluid dynamics (CFD) simulation of micro-channel polishing was conducted to investigate different abrasive impact angles with different abrasive sizes. The material removal characteristics at different stages were revealed to explain different polishing performance due to the variation of tool mark interval and abrasive size. This study can provide solid scientific basis for the ultra-precision finishing of micro-channel obtained by micro-milling and avoid invalid polishing due to the inappropriate initial surface.

关键词： Tool marks removal Micro-channel fluid jet polishing computational fluid dynamics simulation

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