CFD simulation of fluid flow in a novel prototype radial mixed plug-flow reactor

Majid Rasouli,Seyyed Mohammad Mousavi,Hamidreza Azargoshasb,Oveis Jamialahmadi,Yahya Ajabshirchi 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.64 No.-

This research describes a simulation based on three dimensional computational fluid dynamics (CFD) in a semi-continuous PFR reactor. The commercial software FLUENT 6.3 was employed to solve the governing equations. The gas-liquid flow was modeled using an Eulerian multiphase and k–ε turbulence (RNG) model. Hydrodynamics investigated for different total solid (TS) levels and mixing regime using multiple reference frame (MRF) model within the whole multiphase bioreactor. The simulation results in a prototype reactor are validated against the experimental data. Simulation results indicate that flow pattern within the reactor was highly influenced by the substrate density and viscosity, and stirring intensity. Moreover, substrate density and viscosity are variable according to the TS content. The results demonstrate adequate mixing process providing the required amount and intensity of mixing for uniform distribution of reactor content and needed conditions to improve the reactor performance. Comparison of three impeller mixing speed in a reactor demonstrates that mixing intensity has affected the gas phase above the fluid surface. Such a mixing intensity may create a turbulent region with a homogenous mixture of gas and liquid, which is not suitable for this anaerobic digestion.

Design of a Mixed-Spectrum Reactor With Improved Proliferation Resistance for Long-Lived Applications

Abdalla Abou-Jaoude,Anna Erickson,Nicolas Stauff 한국방사성폐기물학회 2018 방사성폐기물학회지 Vol.16 No.3

Long-lived Small Modular Reactors are being promoted as an innovative way of catering to emerging markets and isolated regions. They can be operated continuously for decades without requiring additional fuel. A novel configuration of long-lived reactor core employs a mixed neutron spectrum, providing an improvement in nonproliferation metrics and in safety characteristics. Starting with a base sodium reactor design, moderating material is inserted in outer core assemblies to modify the fast spectrum. The assemblies are shuffled once during core lifetime to ensure that every fuel rod is exposed to the thermalized spectrum. The Mixed Spectrum Reactor is able to maintain a core lifetime over two decades while ensuring the plutonium it breeds is below the weapon-grade limit at the fuel discharge. The main drawbacks of the design are higher front-end fuel cycle costs and a 58% increase in core volume, although it is alleviated to some extent by a 48% higher power output.

A Study on the Gas-Liquid Mixing Characteristics in Reactor System Using Ejector

ZhenHua Jin,Tony Utomo,HanShik Chung,HyoMin Jeong,YouSik Shin,SangChul Lee 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

The aim of this paper is further studies to achieve deeper understanding in this field. First investigate the influence of operating conditions and design parameters on the hydrodynamics and the mass transfer properties of a loop reactor. This paper provides a literature review on the ejectors applications in the mixing system. A number of studies are grouped and discussed in several topics such as the background, theory of ejector, mixing characteristics, optimization of the system. Since the high efficiencies reactor using ejector widely used in gas-liquid system, especially in a number of chemical and biochemical processes. This is due to their high efficiency in gas dispersion resulting in high mass transfer rate and low power requirements. Thus ejector has been applied to the mixing system. An investigation on hydrodynamics and mass transfer characteristics of gas-liquid ejector has been carried out using three-dimensional CFD modeling.

Design of a Mixed-Spectrum Reactor With Improved Proliferation Resistance for Long-Lived Applications

Abou-Jaoude, Abdalla,Erickson, Anna,Stauff, Nicolas Korean Radioactive Waste Society 2018 방사성폐기물학회지 Vol.16 No.3

Long-lived Small Modular Reactors are being promoted as an innovative way of catering to emerging markets and isolated regions. They can be operated continuously for decades without requiring additional fuel. A novel configuration of long-lived reactor core employs a mixed neutron spectrum, providing an improvement in nonproliferation metrics and in safety characteristics. Starting with a base sodium reactor design, moderating material is inserted in outer core assemblies to modify the fast spectrum. The assemblies are shuffled once during core lifetime to ensure that every fuel rod is exposed to the thermalized spectrum. The Mixed Spectrum Reactor is able to maintain a core lifetime over two decades while ensuring the plutonium it breeds is below the weapon-grade limit at the fuel discharge. The main drawbacks of the design are higher front-end fuel cycle costs and a 58% increase in core volume, although it is alleviated to some extent by a 48% higher power output.

A Study of Mixing System Using Gas-Liquid Ejector

ZhenHua Jin,YouSin Jun,Tony Suryo Utomo,XueSong Li,HanShik Chung,HyoMin Jeong 한국동력기계공학회 2006 한국동력기계공학회 학술대회 논문집 Vol.- No.-

A literature review has been carried out on reactor using gas-liquid ejector. The aim of this paper is further studies to achieve deeper understanding in this field. First to investigate the influence of operating conditions and design parameters on the hydrodynamics and the mass transfer properties of a loop reactor. This paper provides a literature review on the ejectors applications in the mixing system. A number of studies are grouped and discussed in several topics. Such as the background, theory of ejector, mixing characteristics, optimization of the system. Since the high efficiencies reactor using ejector widely used in gas-liquid system, especially in a number of chemical and biochemical processes. This is due to their high efficiency in gas dispersion resulting in high mass transfer rate and low power requirements. Circulation and gas dispersion are achieved when the liquid is injected into the reactors with high velocity which entrain the gas phase and create a fine dispersion of the two phases. Thus ejector has been applied to the mixing system.

염색폐수 처리성능에 대한 호기성 고정 및 유동층 생물막공법과 회전매체를 가진 완전혼합 활성슬러지 공법의 비교연구

김홍태,김규창 한국환경과학회 1999 한국환경과학회지 Vol.8 No.4

This study was conducted to evaluate capability of dyeing wastewater treatment for 3 type reactors. These reactors were Packed Bed Reactor(PBR), Fluidized Bed reactor(FBR) and Moving Media Complete Mixing Activated Sludge reactor(MMCMAS). Experiments of PBR and FBR were performed by various packing ratios and organic loading rates, experiments of MMCMAS were performed by various organic loading rates In order to obtain SBOD_5 removal efficiencies of more than 90%, the F/Mv ratios of PBR, FBR, MMCMAS were 0.11 ㎏BOD/㎏MLVSS·d, 0.12 ㎏BOD/㎏MLVSS·d, and 0.37 ㎏BOD/㎏MLVSS·d, respectively. So MMCMAS system which has more active microorganisms showed better capability of organic removal and also stronger dynamic and shock loadings than those of PBR and FBR. In PBR and FBR, the media packing ratio of 20% showed better performance of organic matters removal effciencies than 10% and 30%, but sludge production rate at media packing ratio of 30% was relatively lower than that of 10% and 20%. When more than 90% organic matters removal efficiency was obtained, the ratios of attached biomass to total biomass at PBR, FBR, MMCMAS were 89∼99%, 87∼98%, and 54∼80%, respectvely. The ratio of attached biomass to total biomass was low in MMCMAS. This was formation of thin biofilm due to shear force between rotating disc and water. The average sludge production rates(㎏VSS/㎏BODrem.) of PBR, FBR and MMCMAS were 0.20, 0.29 and 0.54, respectively.

Ultrasound spray nozzle atomizer as a chemical reaction medium: Evaluation using Villermaux-Dushman test reaction

Mojdeh Basiri,Masoud Rahimi 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.5

The present work illustrates the possibility of atomizing the reactant mixture using an ultrasound spray nozzle atomizer to increase reactant contact surface area. The more surface area of the mist-like spray generated due to the atomization provides a means for mixing of reactants, thereby enhancing the reaction rate. Therefore, this work implements an ultrasound spray nozzle atomizer as a reactor. The micromixing efficiency of this novel reactor was evaluated using the Villermaux-Dushman test reaction protocol. An inlet micromixer was placed upstream of the ultrasonic atomizer reactor to provide an early mixing of the reactants. Two simple Y-shaped micromixers with diameters of 0.8 mm and 1.5 mm were examined as the inlet micromixers. The effects of flow rate ratio, flow rate, reactant concentration and inlet micromixer diameter on micromixing efficiency were investigated. Furthermore, the micromixing time was calculated based on the incorporation model through a detailed mathematical formulation. For the studied ranges of operating conditions, the micromixing time was in the range of 0.1–1 s. The small value of estimated micromixing times confirmed that the proposed technique is a valuable concept for intensifying micromixing in chemical reactors.

Synthesis of mesoporous silica SBA-15 using a dropwise flow reactor

류성철,이종환,문희 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.9

Generally, mesoporous silica materials, such as SBA-15, are hydrothermally synthesized in batch reactors. We synthesized SBA-15 in a dropwise flow reactor, which has several merits, such as short reaction times, continuous operation, and easy scale-up. The reaction system had three parts: a mixer and two reaction channels, one operated at a low temperature of 35 oC for the self-assembly of 2D hexagonal silica structures, and the other operated at a high temperature of over 80 oC to increase the stability of the silica structure. Two different operating schemes were used to mix the two immiscible reactant streams, one with a magnetically driven active mixer and the other with a direct supply of premixed reactants. The dropwise flow reactor with the active mixer instead of the low-temperature reaction channel produced fractured silica particles in the final product. However, when a premixed solution under hydrolysis conditions was employed, the synthesis of mesoporous silica SBA-15 was successful within 2.5 h in the dropwise flow reactor, showing close physical properties to the reference SBA-15 sample obtained in a conventional batch reactor.

Investigation of pressure pulsations in a reactor coolant pump with mixed-flow vaned diffuser and spherical casing

Xide Lai,Daoxing Ye,Bo Yu,Xiaoming Chen,Yaguang Heng 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.1

Pressure pulsations are an important factors that cause unstable phenomena such as vibration and noise in the reactor coolant pump (RCP), which is much more complex than inside a general mixed-flow pump due to its structure and actual operating conditions. It is necessary to figure out its characteristics at different operating conditions in order to meet the high requirements of reliability and safety in both design and operation phases. Pressure pulsations inside the impeller and diffuser vanes was carefully investigated by using 3D unsteady flow simulations of the completed pump at 5 operating conditions. To seek the relationship between the pressure pulsations characteristics and operating conditions, the timedomain and frequency-domain characteristics of pressure pulsations at different locations inside the RCP were analyzed. It has been shown that the dominant frequency of pressure pulsations is mainly governed by the blade-passing frequency due to rotor-stator interaction (RSI) between the impeller and diffuser vanes at all operating conditions, and the amplitude of pressure pulsations mainly depends on the operating discharges. The influence on the peak amplitude of its higher harmonics can be neglected when operating at the design discharge, but cannot be negligible for operating at the smaller discharge. The behavior of pressure pulsations at the inlet of the impeller in circumferential direction is not the same and more intensive on the suction side than the pressure side of a blade at different operating conditions, but it is almost the same at the outlet of the impeller as the interaction between the impeller and diffuser vanes. The maximum amplitude of pressure pulsations mainly depends on the operating discharge and reaches the smallest level at the design operating condition. Due to geometric features of the spherical casing, the vortex flow inside the spherical casing leads to the highly irregular and unsteady pressure pulsations inside flow channel of the impeller and diffuser under the smaller discharge operating conditions, and the amplitude of pressure pulsations in higher frequencies increases with the decreasing of the operating discharge. The amplitude of pressure pulsations inside the whole flow channel distinctly increases when the RCP is operating at the extreme small operating discharge. The spherical casing does have influence on the pressure pulsations inside the impeller and diffuser vanes, the effect is stronger under smaller discharge operating conditions than at larger ones.

소형모듈원전 냉각재펌프 임펠러 최적설계

유제용,김덕수,정재호 한국유체기계학회 2023 한국유체기계학회 논문집 Vol.26 No.4

The authors have studied hydraulic design of reactor coolant pump used for small modular reactor. Computational fluid dynamics was used to evaluate the impeller design. Seven factors for the 3D shape variables of the Impeller were selected as a design variables. As a result of using the response surface method for optimizing the shape of the impeller, we were able to select four major design factors for efficiency. The four factors were the impeller blade lengths, outlet blade angle component, and rake component. Finally, we obtained an efficient impeller design through the optimization of these four factors. The head increasing was 0.4m and the efficiency was improved by 0.5% compared to the original model.