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  • Open Access

    ARTICLE

    Numerical Studies on Thermal and Hydrodynamic Characteristics of LNG in Helically Coiled Tube-in-Tube Heat Exchangers

    Fayi Yan*, Xuejian Pei, He Lu, Shuzhen Zong

    Frontiers in Heat and Mass Transfer, Vol.22, No.1, pp. 287-304, 2024, DOI:10.32604/fhmt.2023.045038

    Abstract As compact and efficient heat exchange equipment, helically coiled tube-in-tube heat exchangers (HCTT heat exchangers) are widely used in many industrial processes. However, the thermal-hydraulic research of liquefied natural gas (LNG) as the working fluid in HCTT heat exchangers is rarely reported. In this paper, the characteristics of HCTT heat exchangers, in which LNG flows in the inner tube and ethylene glycol-water solution flows in the outer tube, are studied by numerical simulations. The influences of heat transfer characteristics and pressure drops of the HCTT heat transfers are studied by changing the initial flow velocity, the helical middle diameter, and… More >

  • Open Access

    ARTICLE

    A CRITICAL REVIEW OF RECENT INVESTIGATIONS ON TWO-PHASE PRESSURE DROP IN FLOW BOILING MICRO-CHANNELS

    Sira Saisorna,b, Somchai Wongwisesb,c,∗

    Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-7, 2012, DOI:10.5098/hmt.v3.1.3007

    Abstract Two-phase pressure drop during flow boiling has been studied for several decades. Obviously, the publications available on micro-channels are relatively small compared with those for ordinarily sized channels. Although the use of micro-channels yields several advantages, the pressure drop taking p lace in these extremely small channels is higher than that in the ordinarily sized channels because of the increased wall friction. The knowledge of the two-phase pressure drop characteristics in addition to heat transfer phenomena is essential to the design and evaluation of the micro-systems. In this paper, recent research on the flow boiling pressure drop in micro-scale channels… More >

  • Open Access

    ARTICLE

    PRESSURE DROP MEASUREMENTS WITH BOILING IN DIVERGING MICROCHANNEL

    Amit Agrawala,*, V.S. Duryodhana, S. G. Singhb

    Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-7, 2012, DOI:10.5098/hmt.v3.1.3005

    Abstract An experimental study of flow boiling through diverging microchannels has been carried out in this work, with the aim of exploring reduction in flow instabilities during boiling in diverging microchannels. Effect of mass flux, heat flux and divergence angle on two phase pressure drop has been studied using deionized water as the working fluid. The experiments are carried out on three test sections with divergence angle of 4, 8 and 12 deg with nearly constant hydraulic diameter (146, 154 and 157 µm respectively), for inlet mass flux and heat flux range of 117 - 1197 kg/m2 -s and 2.5 to… More >

  • Open Access

    ARTICLE

    Computational Verification of Low-Frequency Broadband Noise from Wind Turbine Blades Using Semi-Empirical Methods

    Vasishta Bhargava Nukala*, Chinmaya Prasad Padhy

    Sound & Vibration, Vol.58, pp. 133-150, 2024, DOI:10.32604/sv.2024.047762

    Abstract A significant aerodynamic noise from wind turbines arises when the rotating blades interact with turbulent flows. Though the trailing edge of the blade is an important source of noise at high frequencies, the present work deals with the influence of turbulence distortion on leading edge noise from wind turbine blades which becomes significant in low-frequency regions. Four quasi-empirical methods are studied to verify the accuracy of turbulent inflow noise predicted at low frequencies for a 2 MW horizontal axis wind turbine. Results have shown that all methods exhibited a downward linear trend in noise spectra for a given mean wind… More >

  • Open Access

    ARTICLE

    Research on Cavitation Characteristics and Influencing Factors of Herringbone Gear Pump

    Jinlong Yang, Kwang-Hee Lee, Chul-Hee Lee*

    CMES-Computer Modeling in Engineering & Sciences, Vol.139, No.3, pp. 2917-2946, 2024, DOI:10.32604/cmes.2024.046740

    Abstract Cavitation is a common issue in pumps, causing a decrease in pump head, a fall in volumetric efficiency, and an intensification of outlet flow pulsation. It is one of the main hazards that affect the regular operation of the pump. Research on pump cavitation mainly focuses on mixed flow pumps, jet pumps, external spur gear pumps, etc. However, there are few cavitation studies on external herringbone gear pumps. In addition, pumps with different working principles significantly differ in the flow and complexity of the internal flow field. Therefore, it is urgent to study the cavitation characteristics of external herringbone gear… More >

  • Open Access

    ARTICLE

    Parental Educational Expectations, Academic Pressure, and Adolescent Mental Health: An Empirical Study Based on CEPS Survey Data

    Tao Xu1,*, Fangqiang Zuo1, Kai Zheng2,*

    International Journal of Mental Health Promotion, Vol.26, No.2, pp. 93-103, 2024, DOI:10.32604/ijmhp.2023.043226

    Abstract Background: This study aimed to investigate the relationship between parental educational expectations and adolescent mental health problems, with academic pressure as a moderating variable. Methods: This study was based on the baseline data of the China Education Panel Survey, which was collected within one school year during 2013–2014. It included 19,958 samples from seventh and ninth graders, who ranged from 11 to 18 years old. After removing missing values and conducting relevant data processing, the effective sample size for analysis was 16344. The OLS (Ordinary Least Squares) multiple linear regression analysis was used to examine the relationship between parental educational… More >

  • Open Access

    ARTICLE

    Numerical Study of the Effect of Splitter Blades on the Flow-Induced Noise of Hydraulic Turbine

    Fengxia Shi1,2, Guangbiao Zhao1,*, Yucai Tang1, Haonan Zhan1, Pengcheng Wang1

    Sound & Vibration, Vol.58, pp. 101-117, 2024, DOI:10.32604/sv.2024.047082

    Abstract In order to study the effect of splitter blades on the internal and external sound field of the hydraulic turbine, the paper chose a centrifugal pump with a specific speed ns = 33 reversed as a hydraulic turbine as the research object, and added the short blades on the original impeller to form a new splitter impeller. Based on the Re-Normalization Group (RNG) k-ε turbulence model to conduct numerical simulation for the hydraulic turbine, this thesis calculated the internal and external acoustic field by means of the acoustic boundary element (BEM) and finite element (FEM) and analyzed the noise radiation… More >

  • Open Access

    ARTICLE

    Prediction on Failure Pressure of Pipeline Containing Corrosion Defects Based on ISSA-BPNN Model

    Qi Zhuang1,*, Dong Liu2, Zhuo Chen3

    Energy Engineering, Vol.121, No.3, pp. 821-834, 2024, DOI:10.32604/ee.2023.044054

    Abstract Oil and gas pipelines are affected by many factors, such as pipe wall thinning and pipeline rupture. Accurate prediction of failure pressure of oil and gas pipelines can provide technical support for pipeline safety management. Aiming at the shortcomings of the BP Neural Network (BPNN) model, such as low learning efficiency, sensitivity to initial weights, and easy falling into a local optimal state, an Improved Sparrow Search Algorithm (ISSA) is adopted to optimize the initial weights and thresholds of BPNN, and an ISSA-BPNN failure pressure prediction model for corroded pipelines is established. Taking 61 sets of pipelines blasting test data… More >

  • Open Access

    ARTICLE

    Hydrogen Permeation Characteristics of Pd-Cu Membrane in Plasma Membrane Reactor

    Muhd Hadi Iskandar Abd Razak*, Motoki Tsuda, Yukio Hayakawa, Shinji Kambara

    Energy Engineering, Vol.121, No.2, pp. 259-272, 2024, DOI:10.32604/ee.2023.043615

    Abstract Hydrogen is an alternative energy source that has the potential to replace fossil fuels. One of the hydrogen applications is as a material for Polymer Electrolyte Membrane Fuel Cells (PEMFC) in fuel cell vehicles. High-purity hydrogen can be obtained using a hydrogen separation membrane to prevent unwanted contaminants from potentially harming the PEMFC components. In this study, we fabricated a plasma membrane reactor and investigated the permeation performance of a hydrogen separation membrane in a plasma membrane reactor utilizing atmospheric pressure plasma. The result showed the hydrogen permeation rate increasing with time as reactor temperature is increased through joule heating.… More >

  • Open Access

    ARTICLE

    A Transient-Pressure-Based Numerical Approach for Interlayer Identification in Sand Reservoirs

    Hao Luo1, Haibo Deng1, Honglin Xiao1, Shaoyang Geng2,*, Fu Hou1, Gang Luo1, Yaqi Li2

    FDMP-Fluid Dynamics & Materials Processing, Vol.20, No.3, pp. 641-659, 2024, DOI:10.32604/fdmp.2023.043565

    Abstract Almost all sandstone reservoirs contain interlayers. The identification and characterization of these interlayers is critical for minimizing the uncertainty associated with oilfield development and improving oil and gas recovery. Identifying interlayers outside wells using identification methods based on logging data and machine learning is difficult and seismic-based identification techniques are expensive. Herein, a numerical model based on seepage and well-testing theories is introduced to identify interlayers using transient pressure data. The proposed model relies on the open-source MATLAB Reservoir Simulation Toolbox. The effects of the interlayer thickness, position, and width on the pressure response are thoroughly investigated. A procedure for… More >

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