• 제목/요약/키워드: 2-Phase Flow

검색결과 2,086건 처리시간 0.03초

증발기 입구 배관의 구조 개선을 통한 냉장고 냉매 소음 저감 (Reduction of Refrigerant-induced Noise of the Refrigerator by Modification of the Evaporator Inlet Pipe)

  • 김민성;한형석;김태훈;정의봉
    • 한국소음진동공학회논문집
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    • 제19권10호
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    • pp.1012-1020
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    • 2009
  • This research is focused on the experimental study of the noise induced by two-phase refrigerant flow in the evaporator. The two-phase flow in the evaporator has various flow patterns. The effects of two-phase flow pattern's characteristics on the noise of the evaporator are investigated experimentally. The experimental data shows that the generated noise is mainly related to the layout of the pipe and the certain two-phase flow patterns such as the churn and slug flow. Based on these results, we removed the unnecessary vertical pipe and changed the pipe diameter of the evaporator - inlet into small one in order to avoid the intermittent flow condition. The noise level of newly-designed inlet-pipe of the evaporator was measured experimentally by refrigerant-supplying equipment and compared with that of conventional one.

난류유동장에서 Shear - thinning 유체에 의한 마찰저항 감소에 관한 연구 (A Study on the Drag Reduction by Shear-thinning Fluid in Turbulent Flow Fields)

  • 차경옥;김재근;오율권
    • Journal of Advanced Marine Engineering and Technology
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    • 제21권2호
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    • pp.126-135
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    • 1997
  • Drag reduction in polymer solutions is the phenomenon where by extremely dilute solutions of high molecular weight polymers exhibit frictional resistance to flow much lower than the pure solvent. This effect, largely unexplained as yet, has attracted the attention of polymer scientists and fluid flow specialists. Although applications are beginning to appear, the principle interest to data has been in attempting to relate the effect to the fluid mechanics of turbulent flow. Drag reduction in two phase flow can be applied to the transport of crude oil, phase change system such as chemical reactor, and pool and boiling flow. But the research on drag reduction in two phase flow is not intensively investigated. Therefore, experimental investigations have been carried out to analyze the drag reduction produced by polymer addition in the single phase and two phase flow system. The objectives of the proposed investigation are primarily in identifying and developing high performance polymer additives for fluid transportations with the benefits of turbulent drag. Also we want to is to evaluate the drag reduction in horizontal flow by measuring pressure drop and mean velocity. Experimental results show higher drag reduction using co - polymer(A611P) then using polyacrylamide (PAAM) and faster degradation using PAAM than using A611P under the same superficial velocity.

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VOC 회수를 위한 이젝터 시스템에 관한 수치모사 및 실험적 연구 (Numerical Simulation and Experimental Study on an Ejector System for VOC Recovery)

  • 김현동;이동엽;김윤기;정원택;안주하;김경천
    • 한국가시화정보학회지
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    • 제9권2호
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    • pp.54-60
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    • 2011
  • This paper is a basic study on volatile organic compounds(VOC) recovery system in a crude oil carrier. VOC is easily evaporated in cargo tankers during loading and transportation of crude oil, causes serious environmental contamination and a huge economic loss. An ejector system is designed to mix VOC gas into crude oil flow to reduce VOC concentration. Detail two-phase flow inside the ejector is simulated using a commercial CFD code. To verify the numerical prediction, a scale-down experiment is conducted. Instead of crude oil and VOC, water and air are used as the working fluids. Flow characteristics and main parameters are obtained by two-phase flow visualization and PIV measurements. Air volume flow rate induced by the ejector is compared with respect to the volume flow rate of water using experimental and numerical results. Overall performance of the two-phase ejector predicted by the CFD simulation agrees well with that of the experiment.

2상 횡유동을 받는 튜브군의 유체탄성 불안정성 (Fluid-Elastic Instability of Tube Bundles in Two-Phase Cross-Flow)

  • 김범식;장효환
    • 대한기계학회논문집
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    • 제15권6호
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    • pp.1948-1966
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    • 1991
  • 본 연구에서는 2상 횡유동을 받는 튜브군의 진동 메카니즘을 규명하기 위한 실험계획의 일환으로 실시된 실험으로부터 튜브군의 유체탄성 불안정성 상수에 관해 고찰하였다. 실험은 먼저 p/d=1.47 및 1.32 튜브군에 대해 수행되었는데, 이들 튜브 군의 결과는 참고문헌에 발표하였다. 본 논문은 후속 실험으로 수행된 p/d=1.22인 튜브군을 사용하여 유체탄성 불안정성 상수를 고찰한 참고문헌의 후속논문이다. 실 험은 액체상태로 부터 99% 보이드율(void fraction)까지 변화된 2상 유동에서 튜브가 유체탄성 불안정성 상태에 도달할 때까지 점진적으로 증가하였다.실험결과는 p/d= 1.32 alc 1.47 튜브군의 유체탄성 불안정성 결과들과 종합. 비교되었다.

협소 사각유로에서 대향류 2상유동의 기공률과 압력구배 (Void Fraction and Pressure Gradient of Countercurrent Two-Phase Flow in Narrow Rectangular Channels)

  • 김병주;정은수;손병후
    • 설비공학논문집
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    • 제13권4호
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    • pp.304-311
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    • 2001
  • An experimental study on the countercurrent two-phase flow in narrow rectangular channels has been performed. The void fraction and the pressure gradient were investigated using air and water in 760 mm long, 100 mm wide. vertical test sections with 2, 3 and 5 mm channel gaps. Tests were systematically performed with downward liquid superficial velocities and upward gas velocities covering 0 to 0.08 and 0 to 2.5 m/s ranges. respectively. the experimental results were compared with the previous correlations, which were mainly for round tubes, and the qualitative trends were found to be in good agreements. However the quantitative discrepancies were hardly neglected. as the superficial gas velocities increased, the void fraction increased and the pressure gradient decreased, where the effects of the liquid superficial velocities were infinitesimal. as the gap width of the rectangular channel increased the void fraction and the 2-phase frictional pressure gradient approached those values for the round tubes. Equi-periphery diameter, rather than the hydraulic diameter, seemed to be more effective in the analysis of two-phase flow behavior.

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수직상향 기액이상류의 유동특성 (Flow Characteristics of Vertical Upward Gas-Liquid Two-Phase Flow)

  • 최부홍
    • Journal of Advanced Marine Engineering and Technology
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    • 제29권4호
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    • pp.377-383
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    • 2005
  • This paper deals with the flow characteristics of air-water two-phase flow in a vertical tube of 10mm I.D. and 600mm in length at an adiabatic condition. The obtained experimental data were covered with the liquid superficial velocity ranging from 0.095m/s to 2.56m/s. and the gas superficial velocity ranging from 0.032m/s to 21.08m/s. The effects of the gas and liquid superficial velocity on the flow pattern transitions, frictional pressure drop, and film thickness and gas-liquid interface roughness were also examined. It was found that the film thickness increased and the liquid film wave length was more longer with the liquid superficial velocity $j_L$ increasing at $j_G$ constant. It was also showed that the frictional pressure drops were experienced in three regions. namely increasing region(bubbly flow), decreasing region (Taylor bubble and slug flows) and re-increasing region (annular flow).

The Characteristics of Two-Phase Flow Distribution in a Bottom Dividing Header

  • Im, Yang-Bin;Kim, Jang-Soo
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권8호
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    • pp.1195-1202
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    • 2004
  • In this paper an experimental study was investigated for two-phase flow distribution in compact heat exchanger header. A test section was consisted of the horizontal bottom dividing header($\phi$: 5 mm, L: 80 mm) and 10 upward circular mini channels ($\phi$: 1.5 mm, L: 850 mm) using an acrylic tube. Three different types of tube intrusion depth were tested for the mass flux and inlet mass quality ranges of 50 - 200 kg/$m^2$s and 0.1 - 0.3, respectively. Air and water were used as the test fluids. The distribution of vapor and liquid is obtained by measurement of the total mass flow rate and the calculation of the quality. Two-phase flow pattern was observed, and pressure drop of each channel was measured. By adjusting the intrusion depth of each channel an uniform liquid flow distribution through the each channel was able to solve the mal-distribution problem.

DEVELOPMENT OF INTERFACIAL AREA TRANSPORT EQUATION

  • ISHII MAMORU;KIM SEUNGJIN;KELLY JOSEPH
    • Nuclear Engineering and Technology
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    • 제37권6호
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    • pp.525-536
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    • 2005
  • The interfacial area transport equation dynamically models the changes in interfacial structures along the flow field by mechanistically modeling the creation and destruction of dispersed phase. Hence, when employed in the numerical thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Accounting for the substantial differences in the transport mechanism for various sizes of bubbles, the transport equation is formulated for two characteristic groups of bubbles. The group 1 equation describes the transport of small-dispersed bubbles, whereas the group 2 equation describes the transport of large cap, slug or chum-turbulent bubbles. To evaluate the feasibility and reliability of interfacial area transport equation available at present, it is benchmarked by an extensive database established in various two-phase flow configurations spanning from bubbly to chum-turbulent flow regimes. The geometrical effect in interfacial area transport is examined by the data acquired in vertical fir-water two-phase flow through round pipes of various sizes and a confined flow duct, and by those acquired In vertical co-current downward air-water two-phase flow through round pipes of two different sizes.

2차원 압축공기-물의 압축성 이상 유동 수치 해석 (Numerical Analysis for Two-Dimensional Compressible and Two-Phase Flow Fields of Air-Water in Eulerian Grid Framework)

  • 박찬욱;이승수
    • 대한기계학회논문집B
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    • 제32권6호
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    • pp.429-445
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    • 2008
  • Two-phase compressible flow fields of air-water are investigated numerically in the fixed Eulerian grid framework. The phase interface is captured via volume fractions of each phase. A way to model two phase compressible flows as a single phase one is found based on an equivalent equation of states of Tait's type for a multiphase cell. The equivalent single phase field is discretized using the Roe‘s approximate Riemann solver. Two approaches are tried to suppress the pressure oscillation phenomena at the phase interface, a passive advection of volume fraction and a direct pressure relaxation with the compressible form of volume fraction equation. The direct pressure equalizing method suppresses pressure oscillation successfully and generates sharp discontinuities, transmitting and reflecting acoustic waves naturally at the phase interface. In discretizing the compressible form of volume fraction equation, phase interfaces are geometrically reconstructed to minimize the numerical diffusion of volume fraction and relevant variables. The motion of a projectile in a water-filled tube which is fired by the release of highly pressurized air is simulated presuming the flow field as a two dimensional one, and several design factors affecting the projectile movement are investigated.

사다리꼴 미세유로의 대류비등 2상유동 : 1부-압력강하 특성 (Convective Boiling Two-phase Flow in Trapezoidal Microchannels : Part 1-Pressure Drop Characteristics)

  • 김병주;김건일
    • 설비공학논문집
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    • 제23권1호
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    • pp.87-94
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    • 2011
  • Characteristics of two-phase pressure drop in microchannels were investigated experimentally. The microchannels consisted of 9 parallel trapezoidal channels with each channel having $205\;{\mu}m$ of bottom width, $800\;{\mu}m$ of depth, $3.6^{\circ}$ of sidewall angle, and 7 cm of length. Pressure drops in convective boiling of Refrigerant 113 were measured in the range of inlet pressure 105~195 kPa, mass velocity $150{\sim}920\;kg/m^2s$, and heat flux $10{\sim}100\;kW/m^2$. The total pressure drop generally increased with increasing mass velocity and/or heat flux. Two-phase frictional pressure drop across the microchannels increased rapidly with exit quality and showed bigger gradient at higher mass velocity. A critical review of correlations in the literature suggested that existing correlations were not able to match the experimental results obtained for two-phase pressure drop associated with convective boiling in microchannels. A new correlation suitable for predicting two-phase friction multiplier was developed based on the separated flow model and showed good agreement with the experimental data.