• Title, Summary, Keyword: Multiphase flow

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Parametric Study on the Characteristics of Multiphase Laminar Flow with Density Difference in Various Microchannels (다양한 형상의 마이크로 채널 내 밀도 차를 가진 다상 층류 유동의 특성에 대한 매개변수 연구)

  • Paek, Seung-Ho;Kim, Dong-Sung;Choi, Young-Ki
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.10
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    • pp.783-788
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    • 2009
  • In this paper, we have performed a parametric study on the characteristics of multiphase laminar flow with density difference in various microchannels. The interface between multiphase fluids is rotated by the gravitational forces induced by density difference. The numerical simulations were carried out via commercial CFD package to study the characteristics of multiphase laminar flow. The results of the numerical simulations in this study were verified by comparing with the previously reported experimental results in the literature. We have also proposed a new dimensionless relationship between dimensionless rotation angle of interface and dimensionless parameters are proposed for square microchannels with various aspect ratios. The dimensionless relationship could be widely applied to the reliable design of various microfluidic devices dealing with multiphase laminar flow.

Hybrid medium model for conjugate heat transfer modeling in the core of sodium-cooled fast reactor

  • Wang, X.A.;Zhang, Dalin;Wang, Mingjun;Song, Ping;Wang, Shibao;Liang, Yu;Zhang, Yapei;Tian, Wenxi;Qiu, Suizheng;Su, G.H.
    • Nuclear Engineering and Technology
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    • v.52 no.4
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    • pp.708-720
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    • 2020
  • Core-wide temperature distribution in sodium-cooled fast reactor plays a key role in its decay heat removal process, however the prediction for temperature distribution is quite complex due to the conjugate heat transfer between the assembly flow and the inter-wrapper flow. Hybrid medium model has been proposed for conjugate heat transfer modeling in the core. The core is modeled with a Realistic modeled inter-wrapper flow and hybrid medium modeled assembly flow. To validate present model, simulations for a three-assembly model were performed with Realistic modeling, traditional porous medium model and hybrid medium model, respectively. The influences of Uniform/Non-Uniform power distribution among assemblies and the Peclet number within the assembly flow have been considered. Compared to traditional porous medium model, present model shows a better agreement with in Realistic modeling prediction of the temperature distribution and the radial heat transfer between the inter-wrapper flow and the assembly flow.

Simulation on mass transfer at immiscible liquid interface entrained by single bubble using particle method

  • Dong, Chunhui;Guo, Kailun;Cai, Qinghang;Chen, Ronghua;Tian, Wenxi;Qiu, Suizheng;Su, G.H.
    • Nuclear Engineering and Technology
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    • v.52 no.6
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    • pp.1172-1179
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    • 2020
  • As a Lagrangian particle method, Moving Particle Semi-implicit (MPS) method has great capability to capture interface/surface. In recent years, the multiphase flow simulation using MPS method has become one of the important directions of its developments. In this study, some key methods for multiphase flow have been introduced. The interface tension model in multiphase flow is modified to maintain the smooth of the interface and suitable for the three-phase flow. The mass transfer at immiscible liquid interface entrained by single bubble which could occur in Molten Core-Concrete Interaction (MCCI) has been investigated using this particle method. With the increase of bubble size, the height of entrainment column also increases, but the time of film rupture is slightly different. With the increase of density ratio between the two liquids, the height of entrained column decreases significantly due to the decreasing buoyancy of the denser liquid in the lighter liquid. In addition, the larger the interface tension coefficient is, the more rapidly the entrained denser liquid falls. This study validates that the MPS method has shown great performance for multiphase flow simulation. Besides, the influence of physical parameters on the mass transfer at immiscible interface has also been investigated in this study.

Simulation of industrial multiphase flows (공학적 관점에서의 다상유동 문제의 수치해석)

  • Han aehoon;Alajbegovic Ales;Seo Hyeoncheol;Blahowsky Peter
    • Proceedings of the KSME Conference
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    • pp.389-392
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    • 2002
  • In many industrial applications, multiphase flow analysis is the norm rather than an exception as compared to more-conventional single-phase investigation. This paper describes the implementation of the multiphase flow simulation capability in the general purpose CFD software AVL FIRE/SWIFT. The governing equations are discretized based on a finite volume method (FVM) suitable fur very complex geometry, The pressure field is obtained using the SIMPLE algorithm. Depending on the characteristics of the multiphase flow to be examined, the user can choose either the two-fluid model or an explicit interface-tracking model based on the Volume-of-Fluid approach. For truly 'multi'-phase flow problems, it is also possible to apply a hybrid model where certain phases are explicitly tracked while the other phases are handled by the two fluid model. In order to demonstrate the capability of the method, applications to the Taylor bubble flow simulations are presented.

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CFD simulation of flow and heat transfer characteristics in a 5×5 fuel rod bundles with spacer grids of advanced PWR

  • Wang, Yingjie;Wang, Mingjun;Ju, Haoran;Zhao, Minfu;Zhang, Dalin;Tian, Wenxi;Liu, Tiancai;Qiu, Suizheng;Su, G.H.
    • Nuclear Engineering and Technology
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    • v.52 no.7
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    • pp.1386-1395
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    • 2020
  • High fidelity nuclear reactor fuel assembly simulation using CFD method is an effective way for the structure design and optimization. The validated models and user practice guidelines play critical roles in achieving reliable results in CFD simulations. In this paper, the international benchmark MATiS-H is studied carefully and the best user practice guideline is achieved for the rod bundles simulation. Then a 5 × 5 rod bundles model in the advanced pressurized water reactor (PWR) is established and the detailed three-dimensional thermal-hydraulic characteristics are investigated. The influence of spacer grids and mixing vanes on the flow and hear transfer in rod bundles is revealed. As the coolant flows through the spacer grids and mixing vanes in the rod bundles, the drastic lateral flow would be induced and the pressure drop increases significantly. In addition, the heat transfer is enhanced remarkably due to the strong mixing effects. The calculation results could provide meaningful guidelines for the design of advanced PWR fuel assembly.

PIV measurement and numerical investigation on flow characteristics of simulated fast reactor fuel subassembly

  • Zhang, Cheng;Ju, Haoran;Zhang, Dalin;Wu, Shuijin;Xu, Yijun;Wu, Yingwei;Qiu, Suizheng;Su, G.H.
    • Nuclear Engineering and Technology
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    • v.52 no.5
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    • pp.897-907
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    • 2020
  • The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

Development of Compressible Three Phases Flow Simulator Based on Fractional Flow Approach (압축성을 고려한 분율 흐름 접근 방식에 근거한 삼상흐름모델 개발)

  • Suk, Hee-Jun;Ko, Kyung-Seok;Yeh, Gour-Tsyh
    • Economic and Environmental Geology
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    • v.41 no.6
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    • pp.731-746
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    • 2008
  • Most multiphase flow simulators following fractional flow approach assume incompressibility of fluid and matrix or consider only two phase flow (water and air, water and NAPL). However, in this study, mathematical governing equations were developed for fully compressible three-phase flow using fractional flow based approach. Also, fully compressible multiphase flow simulator (CMPS) considering compressibilities of matrix and fluid was developed using the mathematical governing equations. In order to verify CMPS, the CMPS were compared with analytical solution and the existing multiphase flow simulator, MPS, which had been developed for simulating incompressible multiphase flow (Suk and Yeh 2007; Suk and Yeh 2008). According to the results, solutions of CMPS and MPS and analytical solutions are well matched each other. Thus, it is found that CMPS has the capability of simulating compressible three phase flow phenomena assuming compressibilities of fluids and matrix.

NUMERICAL CODE DEVELOPMENT OF THE MULTIPHASE FLOW AROUND AN UNDERWATER VEHICLE UNDER SUBMARINE WAKE. (후류중에 있는 수중운동체의 캐비테이션 유동 현상 및 유체력 변화 해석 코드 개발)

  • Park, S.I.;Ha, C.T.;Park, W.G.;Lee, K.C.
    • 한국전산유체공학회:학술대회논문집
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    • pp.115-121
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    • 2010
  • Cavitating flow is widely shown in many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work focuses on the numerical analysis of the multiphase flow around the underwater vehicle which was launched from a submarine. The governing equation is the Navier-Stokes equation with a homogeneous mixture mode. The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinate. For the code validation, the results from the present work are compared with the existing experimental and numerical results, and a reasonably good agrements are obtained. The multiphase flow around an underwater vehicle is simulated which includes submarine wake effects.

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Assessment of ECCMIX component in RELAP5 based on ECCS experiment

  • Song, Gongle;Zhang, Dalin;Su, G.H.;Chen, Guo;Tian, Wenxi;Qiu, Suizheng
    • Nuclear Engineering and Technology
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    • v.52 no.1
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    • pp.59-68
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    • 2020
  • ECCMIX component was introduced in RELAP5/MOD3 for calculating the interfacial condensation. Compared to other existing components in RELAP5, user experience of ECCMIX component is restricted to developmental assessment applications. To evaluate the capability of the ECCMIX component, ECCS experiment was conducted which included single-phase and two-phase thermal mixing. The experiment was carried out with test sections containing a main pipe (70 mm inner diameter) and a branch pipe (21 mm inner diameter) under the atmospheric pressure. The steam mass flow in the main pipe ranged from 0 to 0.0347 kg/s, and the subcooled water mass flow in the branch pipe ranged from 0.0278 to 0.1389 kg/s. The comparison of the experimental data with the calculation results illuminated that although the ECCMIX component was more difficult to converge than Branch component, it was a more appropriate manner to simulate interfacial condensation under two-phase thermal mixing circumstance, while the two components had no differences under single-phase circumstance.

An experimental study on two-phase flow resistances and interfacial drag in packed porous beds

  • Li, Liangxing;Wang, Kailin;Zhang, Shuangbao;Lei, Xianliang
    • Nuclear Engineering and Technology
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    • v.50 no.6
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    • pp.842-848
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    • 2018
  • Motivated by reducing the uncertainties in quantification of debris bed coolability, this paper reports an experimental study on two-phase flow resistances and interfacial drag in packed porous beds. The experiments are performed on the DEBECO-LT (DEbris BEd COolability-Low Temperature) test facility which is constructed to investigate the adiabatic single and two phase flow in porous beds. The pressure drops are measured when air-water two phase flow passes through the porous beds packed with different size particles, and the effects of interfacial drag are studied especially. The results show that, for two phase flow through the beds packed with small size particles such as 1.5 mm and 2 mm spheres, the contribution of interfacial drag to the pressure drops is weak and ignorable, while the significant effects are conducted on the pressure drops of the beds with bigger size particles like 3 mm and 6 mm spheres, where the interfacial drag in beds with larger particles will result in a descent-ascent tendency in the pressure drop curves along with the fluid velocity, and the effect of interfacial drag should be considered in the debris coolability analysis models for beds with bigger size particles.