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Numerical Study on the Effect of Rim Seal Slot Filleting on Turbine Endwall Cooling Performance

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SSRN 2023年

作者： Shi, Liuliu Di, Wentao School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Key Laboratory of Power Machinery and Engineering Ministry of Education Shanghai Jiao Tong University Shanghai200240 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

In the present study, the effect of rim seal slot filleting on turbine endwall cooling performance is numerically investigated. Based on validation of the numerical method, the Reynolds-averaged Navier-Stokes (RANS) equations combined with the standard turbulence model are adopted in this study. For comparison with the baseline case, five different fillet radii are adopted, i.e. R/W=1.25, 2.5, 3.75, 5 and 6.25. The results indicate that the overall film cooling effectiveness on the turbine endwall can be improved by up to 10% with smaller fillet radii. However, this effect diminishes as the fillet radius increases and it becomes negative at R/W=6.25. By examining the contours of the endwall film cooling effectiveness in filleted cases with the baseline, a prominent strip can be observed across the blade passage. This reveals that the primary contributor to the variation of the film cooling performance is the pressure-side leg horseshoe vortex. Besides, the film cooling effectiveness is slightly improved near the suction side of the leading edge owing to the suppression of endwall separation at this area. The rim seal slot filleting eliminates the slot leakage separation, which in turn speeds up the endwall coolant flow. Ultimately, this weakens the pressure-side leg horseshoe vortex and subsequently enhances the film cooling performance. As the fillet radius continues to increase, the through-flow area for the coolant flow enlarges, resulting in a gradual decrease in film cooling performance. © 2023, The Authors. All rights reserved.

关键词： Turbulence models

Theoretical research on heating the feedwater of thermal power units using jet heat pump

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Theoretical research on heating the feedwater of thermal pow...

2nd International Workshop on Heat Transfer Advances for Energy Conservation and Pollution Control(IWHT2013)(2013年第二届节能减排传热进展国际研讨会)

作者： Wei Han Guangyao Liu Jiping Liu Daotong Chong Jinshi Wang Junjie Yan Moe Key Laboratory of Thermo-Fluid Science and Engineering Xi''an Jiaotong University Xi''an China China HuaDian Electric Research Institute Hangzhou 310030 Hangzhou China State Key Laboratory of Multiphase Flow in Power Engineering Xi''an Jiaotong University Xi''an China

The feedwater temperature of thermal power unit always decreases with the electrical *** order to solve this problem, the ejector heat pump is integrated with the regenerative *** live steam is used to inject the extraction steam of regenerative system, then the mixture steam is led to the added heater (working in low load condition, named as low load condition heater bellow) to heat the feedwater.

关键词： Feedwater Jet heat pump Low load

Pool Boiling Heat Transfer Enhancement on the Hybrid Surfaces Coupling Capillary Wick and Minichannels

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SSRN 2022年

作者： Zhang, Yonghai Ma, Xiang Wang, Jinyu Liu, Wanbo Wei, Jinjia School of Chemical Engineering and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Pool boiling heat transfer can fully utilize the latent heat of the vaporization, to meet the heat dissipation needs of high-power electronic components. In this study, several enhanced hybrid surfaces were designed and processed by sintering spherical copper powder on the minichannels in different ways. The coupled effects of various parameters of capillary wick and minichannels were considered to enhance the pool boiling heat transfer performance of these hybrid surfaces using HFE-7100 as the working fluid. The bubble dynamic behaviors were captured and analyzed by the high-speed camera. The results indicate that the ring groove around the minichannels and the capillary wick have a significant impact on the boiling heat transfer of these hybrid surfaces. This is because the capillary wick provide a large number of nucleation sites and large specific surface area, which can greatly reduce the contact thermal resistance between the capillary wick and the minichannels. At ΔTsub = 30 K, the critical heat flux (CHF) of hybrid surfaces coupling capillary wick and minichannels is up to 147.4 W/cm2, and its maximum heat transfer coefficient (HTC) is 2.69 W/(cm2·K). Compared with minichannels without capillary wick covered, the CHF and HTC are increase by 86.8% and 192.0%, respectively. Furthermore, a correlation for predicting CHF on these hybrid surfaces covered capillary-wick is proposed. Dimensionless parameters such as the subcooled Jakob coefficient (Jasub), the outer surface area enhancement ratio (AER), the particle distribution coefficient (PDC) and the ratio of inner to outer surface area of capillary wick (IOR) are defined to estimate the effect of different factors on the CHF. © 2022, The Authors. All rights reserved.

关键词： Heat flux

Design and Optimal Thermal Efficiency Contrastive Analysis on Closed Brayton Cycle Systems with Different Fluids of Fluoride-Salt-Cooled High-Temperature Advanced Reactor

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SSRN 2022年

作者： Li, Xinyu Zhang, Dalin Yun, Shichang Zhou, Xingguang Jiang, Dianqiang Lv, Xindi Feng, Zhenyu Wu, Wenqiang Tian, Wenxi Qiu, Suizheng Su, Guanghui Zhao, Quanbin Liu, Xiuting State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology Nuclear Power Institute of China Chengdu610213 China

To match the advantages of Fluoride-Salt-cooled high-Temperature Advanced Reactor, the closed Brayton cycle system was selected as the energy conversion system, and the thermodynamic analysis, conjugate gradient optimization, and exergy analysis were performed. The pinch point constraint method based on simultaneous equations was proposed to improve the calculation efficiency and ensure the unity of comparison standards, and the exergy analysis was used to quantify and optimize the exergy losses for the equipment. For the simple regenerative cycle configuration, the thermal efficiency and mass flow rate of the cycle system with various fluids (far-critical fluids: air, nitrogen, helium, and argon, near-critical fluids: carbon dioxide, sulfur hexafluoride, propane, and xenon) were analyzed. The results of the thermodynamic analysis show that the thermal efficiency of the sulfur hexafluoride cycle is the highest and reaching 46.6% with the simple regenerative cycle configuration. The thermal efficiency of the far-critical fluid cycle is more sensitive to turbine efficiency. The results of the exergy analysis show the CO2 cycle has the highest potential to improve thermal efficiency, which has the highest improvement from 43.48% to 49.31% with the recompression process. The method and conclusion of this paper can provide references for the design and optimization of the Brayton power cycle system © 2022, The Authors. All rights reserved.

关键词： Carbon dioxide

Design and Optimal Thermal Efficiency Analysis on Closed Brayton Cycle System of Fluoride-Salt-Cooled High-Temperature Advanced Reactor (Fustar)

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SSRN 2022年

作者： Li, Xinyu Zhang, Dalin Yun, Shichang Zhou, Xingguang Jiang, Dianqiang Lv, Xindi Feng, Zhenyu Wu, Wenqiang Tian, Wenxi Qiu, Suizheng Su, G.H. Zhao, Quanbin Liu, Xiuting State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology Nuclear Power Institute of China Chengdu610213 China

To match the advantages of Fluoride-Salt-cooled high-Temperature Advanced Reactor (FuSTAR): the high temperature, inherent safety, compact structure, and modularization, the closed Brayton cycle system was selected as the energy conversion system, and the enthalpy analysis, conjugate gradient optimization, and exergy analysis were performed. The pinch point constraint method based on simultaneous equations was proposed to improve the calculation efficiency and ensure the unity of comparison standards, and the exergy analysis was used to quantify and optimize the exergy losses for the equipment. For the simple regenerative cycle configuration, the thermal efficiency and mass flow rate of the cycle system with various fluids (far-critical fluids: air, nitrogen, helium, and argon, near-critical fluids: carbon dioxide, sulfur hexafluoride, propane, and xenon) were analyzed, at the highest thermal efficiencies. The results of enthalpy analysis show that the thermal efficiency of the sulfur hexafluoride cycle is the highest with the simple regenerative cycle configuration. The thermal efficiency of the far-critical fluid cycle is more sensitive to turbine efficiency. The exergy analysis shows the CO2 cycle has the highest potential to improve thermal efficiency. The method and conclusion of this paper can provide references for the design and optimization of the Brayton power cycle system. © 2022, The Authors. All rights reserved.

关键词： Enthalpy

Thermal Characteristics and Structural Parameters Optimization of Apg/Cu/Pcm Integrated Architecture

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SSRN 2024年

作者： Su, Lizheng Zhang, Tianning Li, Xiaoyang Li, Dong Jiang, Xinyu Xie, Zhongnan Xi'an Electronic Engineering Research Institute Xi’an710100 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China State Key Laboratory of Nonferrous Metals and Processes GRINM Group Co. Ltd. Beijing100088 China

The challenges faced by radar seeker primarily stem from inadequate heat dissipation in chips and excessive weight. To address these issues, this study introduces a novel integrated phase-change heat sink architecture, composed of a copper alloy matrix, annealed pyrolytic graphite (APG), and phase-change materials (PCMs) serving as heat conduction reinforcements. The numerical analysis of the heat dissipation performance of this architecture is conducted using Fluent software. The study evaluates the impact of APG anisotropy, APG/Cu interface thermal resistance, APG thickness, and surface area on the heat conduction efficiency. Results demonstrate that APG facilitates a uniform in-plane temperature distribution, allowing PCMs to absorb heat more evenly. Consequently, APG proves effective in enhancing heat dissipation and safeguarding chips from high temperatures. In comparison to a pure copper component, the APG/Cu/PCM structure reduces chip temperature by a substantial 56.27%. Furthermore, increasing the surface area of APG generally contributes to an enhanced heat transfer capability of entire architecture. The paper presents a quantitative relationship between APG surface area and optimal thickness. Importantly, APG satisfies the lightweight requirement, further emphasizing its suitability for addressing the thermal challenges in radar seeker structures. © 2024, The Authors. All rights reserved.

关键词： Phase change materials

Development of a Two-Phase flow Solver with Drift-Flux Model Based on Openfoam: Validation Against Single/Two-Phase and Boiling flow

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SSRN 2024年

作者： Wu, Wenqiang Zhang, Dalin Huang, Tao Du, Peng Zhou, Lei Wang, Bo Deng, Jian Qiu, Zhifang Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China

Based on the open-source platform OpenFOAM, this paper implements a two-phase flow solver for drift flux models with realistic closure relations. The solver inherits the numerical method from the OpenFOAM framework, adopts the PIMPLE algorithm, and follows its discrete and matrix-solving criteria, focusing on developing a two-phase flow model and constitutive models. The drift velocity model is based on Ishii and his collaborators’ work. The remaining models, such as wall friction, wall heat transfer, interfacial heat and mass transfer, are taken from TRACE Theory Manual. To fulfill the condition of conjugate heat transfer between fluid and solid, a virtual solid heat transfer function is developed under the premise of a single-domain solver. Extensive and successful validation has been conducted involving single-phase, two-phase, and boiling flow heat transfer phenomena by comparing with experimental data or typical system codes, and the two-phase flow solver's success has been demonstrated in several aspects. © 2024, The Authors. All rights reserved.

关键词： Two phase flow

The Proposal and Calculation Method of the Annular Domain Weight Function for the Electromagnetic flowmeter Under Annular Conductivity Distribution

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SSRN 2024年

作者： Yang, Yang Yang, Biaohu Zhang, Chao Yang, Bin 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 University of Shanghai for Science and Technology Shanghai200093 China

The electromagnetic flowmeter has many advantages, including non-invasiveness, absence of movable parts, high reliability, and insensitivity to physical properties of fluid such as density, temperature, pressure, and viscosity. However, it is susceptible to the impact of non-uniform distribution of medium conductivity. Therefore, studying the characteristic of weight function distribution under non-uniform conductivity distribution is of significant importance for expanding the engineering applications of electromagnetic flowmeter. This includes the case where the conductivity distribution is annular. In this paper, the influence of annular feature input parameters on the weight function distribution is explored by changing the radial distribution size and conductivity ratio of the center and outer ring under annular conductivity distribution. The research results indicate that annular feature input parameters will have complex effects on the distribution of weight function for electromagnetic flowmeter. However, an important finding is that the average value of the weight function within any small annular domain of the center or outer ring remains constant as the radial position changes. Therefore, this paper innovatively proposes the concept of ‘annular domain weight function’. It utilizes the average weight function of the center and outer ring to represent the contribution of the induced electromotive force generated by the average flow velocity within the center and outer ring under axisymmetric flow distribution to the potential difference between the two electrodes. Furthermore, the relationship between the ratio of the annular domain weight function of the center and outer ring and the annular feature input parameters is further studied. Ultimately, the expressions for calculating the weight function of the center and outer ring are obtained. This will be crucially significant for establishing theoretical response model for electromagnetic flowmeter under an

关键词： Distribution functions

Study of flow Pattern Transition Criterion and Heat Transfer Characteristics in Vertical Rectangular Narrow Channel for Steam Heating

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SSRN 2023年

作者： Gu, Shengjie Tao, Leren Jin, Cheng Ju, Yiwei Zhao, Xiefei 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 and Engineering University of Shanghai for Science and Technology Shanghai200093 China

To clarify the heat transfer characteristics of flow boiling in a narrow vertical rectangular channel at each stage and optimise the performance of the heat exchanger, an experimental study of the flow pattern and local heat transfer characteristics in a narrow vertical rectangular channel of steam heating with dimensions of 1400 mm × 250 mm × 2.75 mm (l × w × s) was carried out using deionized water as the working medium. Based on the mechanical model and the empirical formulas of the researchers, the preliminary derivation of the flow pattern transition criterion in the vertical rectangular narrow channel for steam heating is obtained. The effects of inlet temperature, mass flux and heating power on the local heat transfer characteristics were analyzed in conjunction with the flow patterns, and based on the parametric analysis of the experimental data, a new flow boiling heat transfer correlation formula was obtained which applies to the experimental conditions in this paper. The results show that the increase in inlet temperature has a positive effect on the nucleate boiling section, while the degree of effect on the local heat transfer coefficient is minimal after entering the churn flow phases. The increase in mass flux decreases the local heat transfer coefficient in the nuclear state boiling stage and enhances the local heat transfer coefficient in the evaporation zone of liquid film flow. The peak of the local heat transfer coefficient shows a tendency to shift to the left as the heating power increases. The new heat transfer correlation equation can well predict the local heat transfer coefficient of flow boiling in a vertical rectangular narrow channel heated by steam in this experimental condition. © 2023, The Authors. All rights reserved.

关键词： flow patterns