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Numerical Analysis of Turbulent Flow around Tube Bundle by Applying CFD Best Practice Guideline (CFD 우수사례 지침을 적용한 관 다발 주위의 난류유동 수치해석)

  • Lee, Gong Hee;Bang, Young Seok;Woo, Sweng Woong;Cheng, Ae Ju
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.10
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    • pp.961-969
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    • 2013
  • In this study, the numerical analysis of a turbulent flow around both a staggered and an inline tube bundle was conducted using ANSYS CFX V.13, a commercial CFD software. The flow was assumed to be steady, incompressible, and isothermal. According to the CFD Best Practice Guideline, the sensitivity study for grid size, accuracy of the discretization scheme for convection term, and turbulence model was conducted, and its result was compared with the experimental data to estimate the applicability of the CFD Best Practice Guideline. It was concluded that the CFD Best Practice Guideline did not always guarantee an improvement in the prediction performance of the commercial CFD software in the field of tube bundle flow.

A Study on Fluid Flow and Heat Transfer of a Corrugated Structure for Crossflow Reduction of Impingement Jet (충돌제트에서의 횡방향 유동 감소를 위한 파형 구조의 유동 및 열전달에 관한 연구)

  • Hwang, Byeong Jo;Kim, Seon Ho;Joo, Won Gu;Cho, Hyung Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.5
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    • pp.329-339
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    • 2017
  • Impingement jets have been applied in a wide variety of fields as they provide significantly high heat transfer on the impingement-jet stagnation zone. However, the crossflow in an impingement chamber developed by spent wall jets can disrupt and deflect the downstream jets in the array, leading to a decrease in the cooling performance of an array of impingement jets. A numerical analysis is made of the fluid flow and heat transfer characteristics in a corrugated structure that traps the spent air in the corrugations between impingement jets and reduces crossflow effects on downstream jets. All computations are performed by considering a three-dimensional, steady, and incompressible flow by using the ANSYS-CFX 15.0 code. The effects of the configuration parameters of the corrugated structure on crossflow reduction of the array of impingement jets are presented and discussed.

Sidewalls Design for a Double-Passage Cascade Model (2피치 유로의 캐스케이드 모델을 위한 벽면설계에 관한 연구)

  • Cho, Chong-Hyun;Cho, Bong-Soo;Kim, Chae-Sil;Cho, Soo-Yong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.8
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    • pp.797-806
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    • 2008
  • In a double-passage cascade apparatus, only two blades are installed in order to increase the accuracy of experimental result by applying bigger blade than the size of multi-blades on the same apparatus. However, this causes difficulties to make correct periodic condition. In this study, sidewalls are designed to meet periodic condition without removing the operating fluid or adjusting tail boards. Surface Mach number on the blade surface is applied to a responsible variable, and 12 design variables which are related with sidewall profile control are selected. A gradient-based optimization is adopted for wall design and CFX-11 is used for the internal flow computation. The computed result shows that it could obtain the same flow structure by modifying only the sidewalls of the double-passage cascade apparatus.

A Study of Vertical Axis Wind Turbine (수직축 풍력터빈에 관한 연구)

  • park, Jung-Cheul
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.10 no.5
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    • pp.389-395
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    • 2017
  • This paper showed the difference in the optimum conditions by using the ANSYS CFX simulation program with the changes of the main-blade angle and sub-blade angle. Main-blade Shape 4,which had angle 45 while other Shapes with angle 0, was increased to 157.2[%] to 263.2[%] in the power and was increased to 110[%] to 250[%] in the power coefficient. Moreover, when the Shape 5 Fin length of main-blade doubled, the power was 70.8[%] when compared with Shape 1 and 27.5[%] with shape 4.If the main-blade geometry equals shape 1 in the case structure, The power of Case1 was increased to 13.3[%] when compared with Case2. Also, the power coefficient was increased to 15.4[%]. When sub-blade angle was 45, main-blade was better than the Fin type than the Bended type. The power of Case4 was increased to 47[%] when compared with Csae1 and increased to 13.6[%] with Case 3. Also, the power coefficient was 46.7[%] when compared with Case 1 and 15.8[%] with Case 3.

The Study of the Separation Efficiency of Wind Power Selector Using Computational Fluid Dynamics (전산유체역학을 이용한 풍력 선별기의 선별효율 연구)

  • Lee, Keon Joo
    • Journal of the Korea Organic Resources Recycling Association
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    • v.21 no.3
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    • pp.74-81
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    • 2013
  • In this study, the separation efficiency of wind power selector (the direction of the air flow of the air to perform gravity separation method) of municipal solid waste which was landfilled was investigated to reduce amount of waste that is designed to increase the recycling rate of wastes for the ANSYS CFX Program's numerical methods with wind through the separator. When a suction device designed to suction 1000mL of a plastic bag, the separation efficiency was 100% and when the wind speed was 0.9 m /sec or more and when the wind speed was 1.6 m / sec or more, the efficiency of plastic bottles in a mixture of 500mL and 1500mL plastic bottle waste was 100% and the aluminum screening efficiency of 250mL aluminum can was 100 % when the wind speed was 2.3 m / sec. In the last, 5mm thick compressed aluminum can efficiency was 90 % when the wind speed was 2.4 m / sec.

STUDY ON THE PERFORMANCE OF THE SHAPE OF THE AIR-LIQUID EJECTOR DIFFUSER (기체-액체 이젝터의 디퓨저 형상에 대한 연구)

  • Jang, Jin-Woo;Sin, Won-Hyeop;Park, Young-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.11
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    • pp.6412-6418
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    • 2014
  • This paper performed a numerical study of an air-liquid ejector. An ejector is a fluid-transportation device that spouts high-pressure fluid from driving pipes using the kinetic energy of the spouted fluid and increases the pressure through the exchange of momentum with the surrounding gases of the lower pressure. The air-liquid ejector was investigated through steady three-dimensional multiphase CFD analysis using commercial software ANSYS-CFX 14.0. Water as the primary fluid is driven through the driving nozzle and air is ejected as the second gas instead of ozone in real applications. The difference in performance according to the shape of the diffuser of the ejector was examined. The results provide deep insight into the influence of various factors on the performance of the air-liquid ejector. The proposed numerical model will be very helpful for further design optimization of the air-liquid ejectors.

A Study on the Development of Low Speed Twin-Hull Form for Seabed Organic Sediment Collection (해저 유기퇴적물 수거를 위한 저속 쌍동형 선형개발 연구)

  • Park, Je-woong;Kim, Do-jung;Oh, Woo-jun;Jeong, Uh-cheul
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.22 no.2
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    • pp.246-252
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    • 2016
  • In this study, conceptual design of the fore-body hull form of catamaran type dredging vessel was performed that can effectively remove the contaminated sediments in coastal seabed. The hull form was simpled for the easy hull construction and the resistance performance was investigated to find out the effect of hull form parameters between variation of waterline and angle of entrance, etc. The relation between resistance performance and characteristics of free surface flows according to variation of bow forms was investigated by model testing in the circulating water channel and using Ansys CFX. The improvement of ship resistance performance to the wave resistance decrease due to improved wave pattern has been verified according to move the stem and the volume of the shoulder to the fore part of the vessel.

Simulation to identify the frost formation of the heat pump outdoor unit (히트펌프 실외기의 서리층 형성을 파악하기 위한 시뮬레이션)

  • Kim, Jong-Ryeol
    • Journal of the Korean Applied Science and Technology
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    • v.36 no.4
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    • pp.1410-1419
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    • 2019
  • In this research, it is to find a method that frost does not form on the outdoor unit to develop a heat pump capable of heating in cold regions. For this reason, we produced an incubator capable of creating an environment of -25℃, and constructed an experimental apparatus so that experiments in the room were possible. However, it is necessary to grasp the characteristics of the air reaching the front of the heat pump outdoor unit installed in the experimental apparatus, and flow analysis was performed using ANSYS CFX, which is general-purpose software. As a result, the flow velocity of the air reaching the front of the outdoor unit in the outdoor unit chamber in the entire region of the simulation conditions (5.0 to 7.5 m/s) has many differences in the upper and lower portions, resulting in a natural state. It turned out that the condition can not be satisfied. Therefore, it is determined that it is necessary to additionally install a frequency divider at the front of the outdoor unit to make the flow velocity constant.

DEVELOPMENT OF A TWO-DIMENSIONAL THERMOHYDRAULIC HOT POOL MODEL AND ITS EFFECTS ON REACTIVITY FEEDBACK DURING A UTOP IN LIQUID METAL REACTORS

  • Lee, Yong-Bum;Jeong, Hae-Yong;Cho, Chung-Ho;Kwon, Young-Min;Ha, Kwi-Seok;Chang, Won-Pyo;Suk, Soo-Dong;Hahn, Do-Hee
    • Nuclear Engineering and Technology
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    • v.41 no.8
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    • pp.1053-1064
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    • 2009
  • The existence of a large sodium pool in the KALIMER, a pool-type LMR developed by the Korea Atomic Energy Research Institute, plays an important role in reactor safety and operability because it determines the grace time for operators to cope with an abnormal event and to terminate a transient before reactor enters into an accident condition. A two-dimensional hot pool model has been developed and implemented in the SSC-K code, and has been successfully applied for the assessment of safety issues in the conceptual design of KALIMER and for the analysis of anticipated system transients. The other important models of the SSC-K code include a three-dimensional core thermal-hydraulic model, a reactivity model, a passive decay heat removal system model, and an intermediate heat transport system and steam generation system model. The capability of the developed two-dimensional hot pool model was evaluated with a comparison of the temperature distribution calculated with the CFX code. The predicted hot pool coolant temperature distributions obtained with the two-dimensional hot pool model agreed well with those predicted with the CFX code. Variations in the temperature distribution of the hot pool affect the reactivity feedback due to an expansion of the control rod drive line (CRDL) immersed in the pool. The existing CRDL reactivity model of the SSC-K code has been modified based on the detailed hot pool temperature distribution obtained with the two-dimensional pool model. An analysis of an unprotected transient over power with the modified reactivity model showed an improved negative reactivity feedback effect.

Design optimization of the staking line for an electric fan blade using CFD (CFD를 이용한 선풍기 날개의 스태킹 라인 최적 설계)

  • Park, Seunghwan;Ryu, Minhyoung;Cho, Leesang;Cho, Jinsoo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.42 no.11
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    • pp.903-910
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    • 2014
  • Electric fans, which consist of axial blades, are operated by the induction motor. In this paper, the objective of this study is the performance improvement of the base model fan using the design optimization. In order to aerodynamic analysis, computational simulations are performed using commercial tool ANSYS-CFX ver. 14.5. And k-ω SST turbulence model is used for the CFD analysis. The design variables are set up as sweep and lean angles. Volumetric flow rate and torque of the fan blades are fixed to objective function. The optimized model is shown the increment of the volumetric flow rate and the reduction of the torque compared with the base model. The experimental procedure is followed KS C 9301. CFD results and experimental results are fairly well matched.