• Title/Summary/Keyword: 간헐류

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Evaluation of the Effect of Annular-to-Intermittent Plow Transition Model on the Dryout Model (환상류-간헐류 천이 모텔이 드라이아웃 모델에 미치는 영향 평가)

  • WU S.I.;Im In Cheol
    • 한국전산유체공학회:학술대회논문집
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    • 2004.03a
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    • pp.220-223
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    • 2004
  • The initial conditions such as the film thickness and the void fraction at the onset of annular flow are required for the analytical dryout model. The Disturbance Wave Instability model(DWI model) is one of the model describing the Annular-to-Intermittent Flow regime Transition(AIFT). The experimental CHF conditions for the uniformly heated tube were compared with the predictions by the modified Levy model, for which the initial conditions at AIFT were estimated by the DWI model. For the flow through long tubes with small inlet subcooling, the effect of AIFT model on the dryout prediction was little. However, the use of DWI model gave better prediction of CHF in a short tube.

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Effect of Intermittent Plasma Discharge on the Hydrocarbon Selective Catalytic Reduction of Nitrogen Oxides (간헐적 플라즈마 방전이 질소산화물의 탄화수소 선택적 촉매환원에 미치는 영향)

  • Kyeong-Hwan Yoon;Y. S. Mok
    • Applied Chemistry for Engineering
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    • v.34 no.5
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    • pp.507-514
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    • 2023
  • The selective catalytic reduction (SCR) of nitrogen oxides (NOx) was investigated in a catalyst (Ag/γ-Al2O3) packed dielectric barrier discharge plasma reactor. The intermittent generation of plasma in the catalyst bed partially oxidized the hydrocarbon reductant for NOx removal to several aldehydes. Compared to using the catalyst alone, higher NOx conversion was observed with the intermittent generation of plasma due to the formation of highly reductive aldehydes. Under the same operating conditions (temperature: 250 ℃; C/N: 8), the NOx reduction efficiencies were 47.5%, 92%, and 96% for n-heptane, propionaldehyde, and butyraldehyde, respectively, demonstrating the high NOx reduction capability of aldehydes. To determine the optimal condition for intermittent plasma generation, the high voltage on/off cycle was adjusted from 0.5 to 3 min. The NOx reduction performance was compared between continuous and intermittent plasma generation on the same energy density basis. The highest NOx reduction efficiency was achieved at 2-min high voltage on/off intervals. The reason that the intermittent plasma discharge exhibited higher NOx reduction efficiency even at the same energy density, compared to the continuous plasma generation case, is that the intermediate products, such as aldehydes generated from hydrocarbon, were more efficiently utilized for the reduction of nitrogen oxides.

Identification of Internal Flow Pattern in Effervescent Atomizers (기체주입노즐의 내부유동양식의 구분)

  • Kim, Joo-Youn;Lee, Sang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.2
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    • pp.306-315
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    • 2000
  • An experimental study was conducted to examine the internal flow patterns inside the mixing chamber of effervescent atomizers. The mixing chamber has the rectangular cross section ($8mm{\times}2mm$) and made of transparent acrylic plate for flow visualization. The parameters tested were the air/liquid ratio (ALR), injection. pressure, and the nozzle orifice diameter. Three different flow regimes were observed; bubbly, annular, and intermittent flows. In the bubbly flow regime, the discharged mixture was disintegrated into drops through the bubble expansion and the ligament breakup. On the other hand, in the annular flow regime, the liquid annulus was disintegrated into small drops by the aerodynamic interaction between the phases due to the high relative velocities between the gas and the liquid. In the intermittent flow regime, the bubble-expansion/ligament-disintegration mode and the annulus-disintegration mode appeared alternatively. The correlations representing the transition criteria between the two-phase flow patterns within the mixing chamber were proposed based on the drift-flux models.

A Study on Two-Phase Flow Pattern of Pure Refrigerants R134a and Rl23 and Zeotropic Mixture R134a/R123 in Horizontal Tubular (R134a 및 Rl23과 비공비 혼합냉매 R134a/R123의 수평관내 이상유동양식에 관한 연구)

  • Lim, Tae-Woo;Kim, Jun-Hyo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.8
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    • pp.1033-1041
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    • 2003
  • Two-phase flow pattern data during horizontal in-tube flow boiling are presented for pure and mixed refrigerants of R134a and Rl23, The flow pattern is observed through tubular sight glasses located at inlet and outlet of the test section, which is made of a stainless steel tube, 2m long with 10mm I.D., 1.5mm wall thickness. The obtained results are compared with the available various correlations for flow pattern. The flow pattern map of Hashizume was in good agreement with the present data except the region of low mass velocity. Weisman flow pattern map was also known to satisfactorily predict data for refrigerants in the region of annular flow. In this study, the flow pattern are simply classified into two groups; stratified(including intermittent, stratified and stratified-wavy) flow and annular flow. The transition quality from stratified to annular flow was obtained by modifying the liquid Froude number.

Prediction of Two-phase Flow Patterns and Noise Evaluation for Evaporator Pipe in a Refrigerator (냉장고 증발기 배관의 2상유동양식 예측 및 소음 평가)

  • Heo, So-Jung;Kim, Min-Seong;Han, Hyung-Suk;Jeong, Weui-Bong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.10
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    • pp.916-923
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    • 2011
  • The refrigerant after the expansion valve interchanges the heat at the evaporator. At this moment, the state of gas and liquid becomes two-phase flow and causes irregular noise. In order to avoid the noise, the two-phase flow pattern should be predicted. In this paper, the procedure to predict the two-phase flow patterns such as churn flow and annular flow was suggested using the CFD software. The experiments using refrigerant-supplying equipment was carried out and the noise levels according to the flow pattern were measured. The flow patterns predicted by this procedure showed good agreement with those by experiments. The churn flow is noisier than annular flow pattern.

수의학강좌 - 소에서 난산 처치 및 분만 전.후 생식기 질병 관리요령

  • Ryu, Il-Seon
    • Journal of the korean veterinary medical association
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    • v.46 no.6
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    • pp.548-561
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    • 2010
  • 최근 국내 소 사육규모의 대규모 및 전업화 추세에 발맞추어 소 사육농가 현장에서 간헐적으로 발생하고 있는 난산의 부적절한 처치, 분만 전 후 생식기질병관리 부정확 등으로 인한 난산 사고나 생식기 질병의 발생을 초래하고 있는 실정에 있다. 따라서 본고는 특히 작금의 대동물임상수의사가 되기 위한 젊은 수의사들이 예전보다는 다소 늘어가고 있는 추세에 발맞추어 소에 있어서 난산처치 및 분만 전 후의 생식기질병 등의 예방관리요령을 정리하여 소 사육농가들에게 생산성 및 번식률을 제고하였으면 하는 바램을 피력하여 본다.

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

  • Kim, Min-Seong;Han, Hyung-Suk;Kim, Tae-Hun;Jeong, Wei-Bong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.10
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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.

디젤류가 오염된 토양에서 공기주입법으로 처리한 토양 판별 인자들의 변화

  • Kim, Yeong-Am;No, Jong-Su;Lee, Dong-Seon;Lee, Yong-Hui
    • Proceedings of the Korean Environmental Health Society Conference
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    • 2005.11a
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    • pp.110-114
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    • 2005
  • 인공적으로 디젤류에 오염시킨 5kg의 토양이 충전된 두 개의 실험 column을 이용해서 외부 온도변화 효과를 최소화하기 위해서 $25^{\circ}C{\pm}2.5$로 유지시켰으며, 유량속도도 10ml/min로 일정하게 유지시켰다. 또한 수분은 활동범위 능력의 $60{\sim}80%$에서 유지시켰다. 따라서 연속식과 간헐 주입식 모드를 운전비용의 감소 및 효율의 향상 측면에서 모드의 평가를 위한 방법으로 이용기간 동안 총세균 수, 유류분해균 수의 변화, 탈수소효소 활성도의 변화 추이 분석을 하였다. 두 venting 모드별로 본 총 종속영양균 수와 유류분해균 수는 모두 대등한 성장률을 보였으며, 반응일 수에 따라 비교된 탈수소효소 활성도 반응 90일 동안 비슷한 활성을 유지 했다.

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A Study on Combustion Characteristics using Forced Pulsating Flow (강제 맥동류를 이용한 연소특성 연구)

  • Yang, Young-Joon
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.5
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    • pp.109-114
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    • 2012
  • The combustion characteristics using forced pulsating flow were experimentally investigated with confined premixed flames stabilized by a reward-facing step. The intermittent combustion has many merits, for instance, such as high load combustion, high heat transfer, low emission gas, compared with those of continuous combustion. For these purposes, data processing of binary image was conducted to reveal the differences between intermittent and continuous combustion. As the results, it was possible to calculate the reaction zone using OH-emission band and, therefore, showed that forced pulsating flow was useful in combustion technology.