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Numerical study of specific C-shaped heat exchanger using porous medium and coarse mesh coupling method

International Journal of Thermal Sciences 2025年 210卷

作者： He, Shaopeng Wang, Shiqi Wang, Mingjun Tian, W.X. Qiu, S.Z. Su, G.H. State Key Laboratory of Multiphase Flow in Power Engineering School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an710049 China

Porous medium method is an effective simplified approach for the heat exchanger simulation when the numerous tubes and complex structures bring unacceptable computational resources to full-scale simulation. However, for the specific C-shaped heat exchanger, the tube side resistance and flow distribution characteristics that significantly affects the heat transfer and natural circulation performance cannot be obtained by the traditional porous medium method coupled with the one-dimensional node model for tube side. It is urgent to develop a new coupling method that can not only simplify modeling and calculation, but also obtain tube side high-resolution flow heat transfer characteristics. This study presents a novel calculation method which couples the porous medium mesh and the tube side coarse mesh. The coupling method was then applied to a typical C-shaped passive residual heat removal heat exchanger (PRHR HX), which is significant to the stable operation and the mitigation of accident conditions in the nuclear power plant. The coupling calculation method was validated against the full-scaled simulation and data from scaled-down experiment. The average relative error of heat transfer power is 2.1 % under steady state conditions. Under transient conditions, the average absolute error of the fluid temperature and wall temperature are less than 6 K. Then the 3D thermal-hydraulic characteristics of PRHR HX was studied. Owing to a greater gravitational pressure head, the mass flow rates in the extended tubes surpass those in the shorter tubes by a relative deviation of 27.4 %. The upper horizontal tube's heat exchange capacity constitutes approximately 70 % of the total power, leading to enhanced natural circulation. The outlet temperatures from various tubes tend to equalize. The boiling area gradually extended down along the heat transfer tubes. Our work would present an innovative calculation method to the numerical study and design optimization of the C-shaped heat

关键词： Nuclear power plants

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Atomization of highly reactive simulant with Hydrogen Peroxide by a liquid–liquid pintle injector

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Acta Astronautica 2025年 233卷 266-276页

作者： Dias, Gabriel Silva da Silva Mota, Fábio Antônio Yao, Xiaoxin Fei, Lihan Tang, Chenglong de Souza Costa, Fernando State Key Laboratory of Multiphase Flows in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China São Paulo Cachoeira Paulista12630-970 Brazil São Paulo Santo André09210-580 Brazil

As interest in green hypergolic propulsion systems grows, the need for further development and a deeper understanding of promising new propellants with versatile injectors becomes crucial. This experimental work employed a pintle injector to investigate the different atomization behaviors of a reactive fuel surrogate. The surrogate was designed to partially mimic the heat release and vapor formation, captured by a time-resolved infrared camera, as well as the recently reported foamy-like structure in hypergolics using hydrogen peroxide solutions as a green oxidizer, captured by a high-speed camera. The dominant foamy-like structure significantly affects the breakup length and spray cone angle behavior of the reactive surrogate/hydrogen peroxide pair compared to a water–water non-reactive case. The average representative diameter of reactive particles was substantially larger and showed different responses to breakup and capillary deformation mechanisms, as detected by inspecting two distinct regions downstream of the injector exit. The particle size distribution exhibited a bimodal pattern for the non-reactive cases and unclear behavior for the non-reactive cases. The calculated particle velocity profile, extracted from a Particle Image Velocimetry analysis tracking droplets and reacting particles, revealed similar behavior for both non-reactive and reactive cases. The breakup process of reacting ligaments in the current study was similar in non-combustion conditions compared to that of ligaments under combustion environments from previous work. Particles smaller than 2 mm remained approximately constant in size until exiting the field of view in the non-combustion case or until extinction due to evaporation in the combustion case. Larger particles changed shape until plateauing in non-combustion, while their equivalent diameter decreased almost linearly due to evaporation in combustion. The D2-law overestimates the evaporation process until the extinction of a liga

关键词： High speed cameras

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Hydrogen production performance optimization for direct-coupled photovoltaic electrolysis systems based on a novel 3D opto-electro-thermal model

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Applied Energy 2025年 392卷

作者： Wang, Hao Wang, Weiding Lin, Chuanjie Lai, Yongquan Li, Changchen Xu, Ziyou Yang, Yuanbo Yang, Yimin Dong, Wenxuan Su, Jinzhan International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi'an Jiaotong University Xi'an710049 China

Photovoltaic-powered electrolysis systems represent a promising approach for large-scale renewable energy storage, with direct-coupled systems offering particular advantages in terms of reduced system complexity and cost. However, a mismatch issue between photovoltaic (PV) and electrolysis (EC) modules of these systems could be caused by suboptimal structural design and flow rate control strategies, leading to a significant reduction in hydrogen production performance. While these problems could potentially be addressed through numerical simulation, existing low-dimension models are overly simplified due to the assumptions of spatial homogeneity, failing to adequately capture the intricate coupling mechanisms among optical, thermal, electrical and gas-liquid flow phenomena in these complex systems. In this study, a novel 3D opto-electro-thermal model has been developed for direct-coupled systems, utilizing semiconductor drift-diffusion equations and a gas-liquid two-phase flow model within each grid cell. This advanced model facilitates comprehensive performance assessments during the optimization of the fundamental system structure (PV-EC), including the evaluation of novel system configurations that integrate photovoltaic/thermal (PV/T) and contact-based thermal designs. Additionally, it could help to streamline flow rate control by optimizing the relative sizing between the membrane electrode assembly (MEA) of EC and PV modules. The results demonstrate that the PV/T-EC Non-thermal integration structure achieves the maximum Solar-to-Hydrogen efficiency (STH). Moreover, by setting the relative sizing at 2.25 %, maintaining the flow rate in a wide range without precise control could be sufficient to achieve outstanding and stable STH under real-world fluctuating conditions. This allows the flow rate control strategy to be effectively streamlined. The findings could provide guidance for optimizing hydrogen production performance by refining system structure and flow

关键词： Model structures

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NUMERICAL STUDY OF THE EFFECT OF PERIODIC WAKE ON FILM COOLING EFFECTIVENESS ON A PLATE

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Thermal Science 2025年第2期29卷 1197-1206页

作者： Shi, Liuliu Fan, Haobo Chen, Eryun School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai China

The research presented in this paper is devoted to exploring the influence of up-stream periodic wake on the film cooling effectiveness on a downstream plate. This investigation is carried out through rigorous numerical simulations utilizing a ded-icated simulation model. The model was developed to examine the impact of up-stream periodic wake on film cooling performance across varying blowing ratios (M = 0.3, 0.5, and 1.0) and wake sweeping frequencies (10 Hz, 20 Hz, and 40 Hz). Comparative analyses are conducted with a baseline scenario involving a constant jet without wake. The objective of these analyses is to provide a deeper understand-ing of the mechanisms through which upstream wake influences film cooling per-formance, ultimately shedding light on the flow characteristics and cooling effec-tiveness of film cooling under sweeping wakes. © 2025 Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia.

关键词： blowing ratio film cooling gas turbine wake

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Flocculation of suspended cohesive particles in Rayleigh-Bénard turbulence

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Physical Review Fluids 2025年第2期10卷 024305-024305页

作者： Han Huang Shuaiqi Zhao Rui Zhang Binbin Pei Kunpeng Zhao Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Key Laboratory of Mechanics on Disaster and Environment in Western China The Ministry of Education of China Lanzhou University Lanzhou 730000 China

We employ a four-way coupled numerical approach to investigate the dynamics of suspended cohesive particles in Rayleigh-Bénard turbulence. The Stokes drag, cohesive, and direct contact forces between primary particles are captured in detail, yielding the phenomena of flocs' aggregation, breakage, and deformation. The momentum and thermal exchange between primary particles and the fluid are considered based on the Source-in-Cell method. We found that the initial increase of the average floc size indicates a temporary flocculation phase, which is followed by an equilibrium phase where the average floc size becomes stable, reflecting the balance between aggregation and breakage. Different from the traditional perspective, which attributed the local accumulation of particles to their gravity, we found that the suspended particles still tend to accumulate in the bottom hot boundary layer region. This accumulation is primarily driven by the temperature-induced variation in aggregation strength and the nonuniform spatial distribution of floc inertia. Additionally, the stronger cohesion yields a reduction in momentum intensity of the thermal plumes, primarily due to the more pronounced weakening of fluid momentum by the larger flocs.

关键词： Momentum

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engineering of Fe d-band center in Fe_(3)O_(4)/CeO_(2)hetero-nanoparticles via orbital coupling for high-efficiency oxygen reduction electrocatalysis

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Nano Research 2025年第1期18卷 129-139页

作者： Jiayi Liu Jingwen Yin Yingzi Lin Mingxin Pang Huan Pang Songtao Zhang Lin Xu Jun Yang Yawen Tang Jiangsu Key Laboratory of New Power Batteries Jiangsu Collaborative Innovation Center of Biomedical Functional MaterialsSchool of Chemistry and Materials ScienceNanjing Normal UniversityNanjing 210023Chin a 2 State Key Laboratory of Multiphase Complex Systems Center of MesoscienceInstitute of Process EngineeringChinese Academy of SciencesBeijing 100190China School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225009China Testing Center Yangzhou UniversityYangzhou 225009China

The deliberate engineering of the d-band center of metal site represents an effective strategy to boost the intrinsic electrocatalytic performance toward the oxygen reduction reaction(ORR).Herein,following a heterointerfaceinduced orbital coupling rationale,we report a judicious design of an efficient ORR electrocatalyst consisting of Fe_(3)O_(4)/CeO_(2)hetero-nanoparticles in-situ encased into N-doped carbon nanofibers(abbreviated as Fe_(3)O_(4)/CeO_(2)@N-CNFs hereafter).The theoretic calculations uncover that the Fe_(3)O_(4)/CeO_(2)heterointerface-triggered orbital coupling can cause the down shift of the d-band center positions of Fe sites,which leads to the weakened chemisorption of oxygenated groups and lowered energy barrier for the potential-determining step,ultimately dramatically boosting the ORR intrinsic *** a consequence,the well-designed Fe_(3)O_(4)/CeO_(2)@N-CNFs display admirable ORR activity with a half-wave potential of 0.84 V and outstanding structural/electrochemical stability in an alkaline electrolyte,surpassing the commercial Pt/C benchmark and a majority of recently reported Fe_(3)O_(4)-based *** encouragingly,the Fe_(3)O_(4)/CeO_(2)@N-CNFsincorporated Zn-air battery outperforms the Pt/C-assembled counterpart with higher power density,larger energy density,and excellent cycling stability,serving as a competent candidate for ORR-involved renewable energy *** study offers an innovative approach for the rational manipulation of the d-band center and interfacial electron behavior of active sites toward the optimization of electrocatalytic performance.

关键词： hetero-nanoparticles electrospinning interfacial engineering orbital coupling oxygen reduction reaction

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Infectious cough droplet dynamics in a makeshift hospital isolation ward

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Physics of Fluids 2025年第2期37卷

作者： Norvihoho, Leslie Kojo Liu, Yi Yin, Jing Zhu, Xin-Gang Yu, Hai-Tao Wang, Qi-Di Chen, Bin Zhou, Zhi-Fu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China China Nuclear Power Engineering Co. Ltd. Beijing China

The COVID-19 pandemic highlighted the need for rapidly deployable healthcare facilities, leading to increased use of modular construction methods. Nonetheless, knowledge about airflow patterns and the spread of bioaerosols in these wards remains insufficient, potentially heightening the risk of cross-infection among healthcare workers and patients. This paper presents a ventilation design for a modular negative-pressure ward aimed at reducing the spread of infectious particles. We investigate the effects of various ventilation designs, patient postures (sitting and supine), and air changes per hour (ACH) on the spread of infectious cough droplets in an airborne infection isolation room using large eddy simulation and the Eulerian-Lagrangian model. Findings show that ceiling exhaust grilles (design 2) resulted in the lowest radial dispersion (3.64 m) at 12 ACH, while sidewall exhausts (baseline) performed best at higher ACH levels. Seated patients had quicker droplet evaporation compared to those in a supine position. The best setups for reducing droplet survival included exhaust grilles at the bed's bottom and ceiling, maintaining a minimum of 12 ACH. Cases 5 and 13, with grilles over the patient's head and at the bed's bottom, showed the lowest concentrations of DPM, under 0.008 km−3 near the source and less than 0.001 km−3 mid-room. Sitting posture consistently led to lower DPM concentrations. This research emphasizes the critical role of exhaust placement in reducing droplet re-circulation and transmission risks, ultimately contributing to improved ventilation strategies and infection control in AII rooms. © 2025 Author(s).

关键词： Ceilings

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Experimental and simulation study of H 2 crossover in PEM water electrolysis for high-pressure hydrogen production up to 20 MPa

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International Journal of Hydrogen Energy 2025年 135卷 499-506页

作者： Jiazhe Wu Guoao Zhang Boyu Dong Yuhao Chang Yubin Chen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi 710049 P. R. China

High-pressure proton exchange membrane (PEM) water electrolysis offers considerable advantages, particularly in enabling direct integration with hydrogen storage and transportation systems while eliminating the need for external mechanical compressors. However, H 2 crossover is a bottleneck that induces high H 2 -in-O 2 content and low overall efficiency during high-pressure PEM water electrolysis. This study investigates H 2 crossover in PEM water electrolysis by combining in situ measurements and numerical simulations over a differential pressure range of 0–20 MPa. A linear correlation was observed between hydrogen crossover and current density within the range of 0–1 A cm −2 . The cathodic hydrogen mass transfer coefficient was determined to range from 1.6 to 3.2 mm s −1 , and the hydrogen solubility was estimated as 1.1 × 10 −3 mmol m −3 Pa −1 . The results highlight the importance of optimizing mass transfer and reducing hydrogen solubility within the cathode catalyst layer to mitigate H 2 crossover during high-pressure PEM water electrolysis.

关键词： High-pressure hydrogen Hydrogen crossover Proton exchange membrane Water electrolysis

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Novel numerical method establishment and performance evaluation for rotary adsorption and desorption wheel for carbon capture

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Applied Thermal engineering 2025年 274卷

作者： Gao, Rongze Wang, Limin Wang, Chang'an Tang, Chunli Li, Yuhang Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China School of Mechanical Engineering Xi'an Shiyou University Xi'an710065 China

Due to the great compactness and ease of operation, the rotary adsorption and desorption wheel (RADW) is applicable for carbon capture in power plants using temperature swing adsorption (TSA). Commercial CFD-based software such as Fluent is commonly used to evaluate the RADW performance but the computing time is too long. However, few studies have focused on the computational efficiency and stability of complicated coupled heat and mass transfer processes in the RADW. A detailed iteration format and method for independent programming is urgently needed for both rapid design calculation and real-time performance monitoring in power plants. A novel rapid solution method using the mixed implicit and explicit (MIE) strategy to achieve the cyclic steady state (CSS) in the rotary bed was proposed, which can be used for heat transfer, mass transfer, and the coupled transfer processes. A comparison in terms of accuracy and efficiency was made between Fluent and the proposed method. In order to illustrate the applicability and universality of the proposed method, characteristics of the mass and temperature distribution in the RADW packed with amine-functionalized G3M were obtained, and the effects of different parameters on the adsorption and desorption behavior of RADW were studied. The correlation for the adsorption efficiency calculation operation was fitted, with which the adsorption efficiency under different operating conditions can be quickly obtained. © 2025

关键词： Osmosis

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Experimental Study on Heat Transfer Characteristics of Supercritical Carbon Dioxide in a Vertical Circular Tube

SSRN

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SSRN 2025年

作者： Yang, Haikuo Nie, Ruishan Zhang, Kui Tian, Wenxi State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

Supercritical carbon dioxide (S-CO2) nuclear energy and power systems have garnered significant attention for flow and heat transfer experiments because of their compact design, advanced circulation methods, and high thermal efficiency, aligning with future trends in nuclear power plant development. However, the dramatic change in physical properties of S-CO2 near its pseudo-critical point can lead to heat transfer deterioration (HTD) in heat exchangers, potentially damaging the S-CO2 Brayton system. This paper presents an experimental study on the HTD of S-CO2 in a vertical circular tube under forced circulation, examining how heat flux, inlet temperature, and system pressure influence *** analysis delves into the mechanisms of HTD, focusing on the buoyancy and flow acceleration effects. Additionally, the study explores the impact of heat flux and system pressure on S-CO2 natural circulation. Ultimately, the research summarizes the flow and heat transfer characteristics of S-CO2 and proposes a new heat transfer correlation formula, demonstrating an error margin within ±25%, which meets practical engineering requirements. This experimental study contributes valuable data to the understanding of flow and heat transfer phenomena in S-CO2, offering significant insights for future applications. © 2025, The Authors. All rights reserved.

关键词： Nuclear energy

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