• Title/Summary/Keyword: 직경증가

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Mixing Performance of Unlike Doublet Impinging Liquid Jets (이중 충돌제트의 혼합 성능 연구)

  • Jo, Yong Ho;Lee, Seong Ung;Yun, Ung Seop
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.4
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    • pp.82-91
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    • 2003
  • Experiments to investigate the mixing performance of unlike doublet impinging jets are conducted. Reynolds number of simulants used in this study rages from 1.0 to 1.5 Cold flow test is performed to investigate the hydrodynamic effect and spray of the impinging jets are collected locally and calculated by using Rupe's mixing efficiency equation. Momentum exchanges and relative velocity ratio between two jets are taken as the main parameter to represent the effect of enlargement of the orifice diameter. As diameter ratio increases, the corresponding momentum ratio where maximum mixing efficiency occurs and relative velocity at the maximum mixing efficiency ranges 0.6 to 0.7, respectively. Penetration depth can be taken as a prominent parameter to estimate the mixing efficiency.

Study on Performance Evaluation of Mixing Section of Ejector using CFD simulation (CFD 시뮬레이션을 이용한 이젝터 혼합실 형상에 따른 성능 평가에 관한 연구)

  • Sin, Won-Hyeop;Kim, Min-Woo;Park, Young-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.5
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    • pp.2610-2616
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    • 2014
  • An ejector is a kind of pump which is using pressure energy of high pressure fluid. This study aims to investigate performance influencing according to change the ejector mixing section shape using CFD simulation by Finite Volume Method. Optimum conditions were suggested 3 kind of variable such as nozzle diameter, nozzle length, distance from nozzle tip to the diffuser inlet. The results, It was confirmed that the diameter of the nozzle was the greatest effect in performance of the ejector. The diameter of the nozzle get smaller, mixing ratio was increased. On the other hand, nozzle length, distance from nozzle tip to the diffuser inlet had little effect on performance. It was proposed specific Mixing section, Nozzel diameter 23.8mm using the Artificial Neural Network.

Comparison in Cultural Characteristics According to Pot Diameter and Substrate Weight in Pot Cultivation of Pleurotus ostreatus (느타리버섯 봉지재배시 봉지직경 및 배지량에 따른 생육 특성 비교)

  • Lee, Yun-Hae;Cho, Yun-Jeong;Kim, Hee-Dong
    • The Korean Journal of Mycology
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    • v.30 no.1
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    • pp.18-22
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    • 2002
  • This study was carried to investigate efficient pot diameter and substrate weight in pot cultivation of Pleurotus ostreatus. Cultivating substrate was pine sawdust+beet pulp+cotten seed flour (50 : 30 : 20, v/v). Ranges of pot diameter and substrate weight were $10{\sim}20\;cm\;and\;600{\sim}2,500\;g/pot$, respectively. Smaller pot diameter resulted in longer pot length according to increasing substrate weight, so mycelial growth period and total cultivation period was retarded. Wider pot diameter resulted in a little lower biological efficiency in the same substrate weight. Heavier substrate weight was brought higher yield but lower biological efficiency. Average yield according to pot diameter was decreased at wider than 14 cm during second flush. And average biological efficiency according to substrate weight was lower than 100% at heavier than 1,200 g/pot during second flush. So suitable pot diameter and substrate weight in pot cultivation of Pleurotus ostreatus were estimated $10{\sim}14\;cm\;and\;800{\sim}1,200\;g$, respectively.

레이놀즈수 변화에 따른 대기압 플라즈마 제트의 방전 특성 변화

  • Kim, Yun-Jung;Jin, Se-Hwan;No, Jun-Hyeong;Song, Seo-Jin;Lee, Ye-Gwon;Choe, Min-Seong;Kim, Hui-Ju;Gwon, Gi-Cheong;Jo, Gwang-Seop
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.240.1-240.1
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    • 2014
  • 대기압 플라즈마 제트 장치에 주입되는 기체의 유량 변화에 따른 방전 특성을 유체역학적으로 해석하였다. 장치에 주입되는 기체의 유량 변화는 레이놀즈수에 의한 유체 흐름의 상태 변화와 베르누이 정리에 의한 압력 변화를 동반한다. 유리관에 주입되는 기체의 레이놀즈수가 Re<2000이면 층류이며 Re>4000이면 난류, 2000

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증기 제트 응축현상에서의 응축하중에 대한 실험적 연구

  • Park, Chun-Kyung;Cho, Seok;Song, Cheol-Hwa;Yang, Seon-Kyu;Cheon, Se-Young;Jeong, Mun-Ki
    • Proceedings of the Korean Nuclear Society Conference
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    • 1998.05a
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    • pp.541-546
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    • 1998
  • 증기 제트 응축에서 발생하는 응축하중을 실험적으로 고찰하였다. 네 가지 서로 다른 직경의 노즐 (5, 10, 15, 20mm) 과 증기분사기를 응축실험에 사용하였으며, 증기 질량유속과 물온도를 변화하면서 동압을 측정하였다. 실험결과에 의하면 압력파의 진폭은 노즐 직경이 작을수록 작았다. 한편 압력파의 진폭은 일반적으로 물온도가 증가할수록 증가하나 물온도가 어느 한도 이상으로 증가하면 오히려 감소하는 경향을 보였다. 그러나 물온도가 아주 높고 증기 질량유속이 큰 경우에는 불안정한 압력파가 발생할 가능성이 관찰되었다.

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An Experimental Investigation of the Underwater Oil Drop Formation (수중으로 방출되는 유류의 유적화에 관한 실험연구)

  • Song Museok
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.6 no.1
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    • pp.3-10
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    • 2003
  • Oil drop formation during the underwater oil discharge is investigated experimentally. The focus is placed on the size of the drops formed with the variation of discharge speed and nozzle diameter. As the Reynolds number based on the nozzle diameter increases, the droplet size decreases first and then increases until an explosive atomization occurs. The length of the jet attached to the nozzle Increases with the Reynolds number and then decreases. The transition occurs when the flow becomes asymmetry.

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Buckling Strength of Cylindrical Shell Subjected to Axial Loads (축하중을 받는 원통형 쉘의 좌굴강도)

  • Kim, Seung Eock;Choi, Dong Ho;Lee, Dong Won;Kim, Chang Sung
    • Journal of Korean Society of Steel Construction
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    • v.13 no.2
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    • pp.191-200
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    • 2001
  • This paper presents buckling analysis of the cylindrical shell subjected to axial loads using numerical method. The modeling method, appropriate element type, and number of element are recommended by comparing with analytical solution. Based on the parametric study, buckling stress decreases significantly as the diameter-thickness ratio increases. These results are different from those obtained from buckling analysis of columns. The number of buckling half-wave in circumferential direction decreases as the diameter-height ratio increases. Buckling stress increases 1~2% as the thickness of base plate increases. Therefore the effect of base plate on buckling strength for cylindrical shell can be disregarded. Buckling stress significantly decreases as the amplitude of initial geometric imperfection used for calculating buckling stress is developed and it shows a good agreement with numerical results.

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방사성 폐기물 유리화를 위한 이송식 아크 플라즈마 전산해석

  • Go, Ju-Yeong;Choe, Su-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.194.1-194.1
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    • 2016
  • 방사성 폐기물의 운반이나 장기 보관 시 방사성 물질의 침출을 차단하기 위한 유리화 기술을 실현하기 위해 이송식 아크 플라즈마에 대해 전산해석을 수행하였다. 본 연구에서는 운전전류나 아크길이와 같은 운전조건 변화에 따른 열플라즈마의 특성 변화 뿐만 아니라 150 kW급 고출력 이송식 아크 플라즈마의 최적 설계를 위하여 핵심 부품인 파일럿 노즐의 길이와 직경 변화에 따른 예상 용융영역을 전산해석 하여 방사성 폐기물의 유리화 기술을 상업적으로 이끌어내는데 기초 자료를 제공하고자 하였다. 노즐직경은 4, 5, 6 mm로 변화시켰으며, 길이는 2, 4, 6mm로 하였다. 이러한 다양한 설계조건에 대하여 운전변수로는 전류 200 A, 방전 기체인 알곤의 유량 15 L/min, 아크 길이 2 cm로 고정하였다. 전산해석 결과 노즐직경이 작을수록 아크압축 효과에 의해 중심부에서 최고 온도가 높은 열플라즈마 제트를 발생시킬 수 있으나, 반경방향으로 온도구배가 커서 고온 구간이 급격히 감소하는 경향이 예상되었다. 반면 노즐직경이 증가할수록 아크 압축효과는 줄어들지만 반경방향으로 온도가 완만히 감소하여 콘크리트가 대부분인 유리화 대상물질을 충분히 용융시킬 수 있는 $2,600^{\circ}C$ 이상의 고온 면적이 넓어지게 될 것으로 예상되었다. 또한, 노즐길이가 줄어들 경우 아크방전의 안정성은 다소 떨어 질 수 있으나 수 있으나 고온의 열플라즈마 제트가 반경방향으로 효과적으로 넓어 질 수 있음이 예측되었다. 따라서 고온 영역의 확장 관점에서 이송식 아크 플라즈마 토치를 제작할 경우 아크의 안정성을 유지하는 범위 내에서 파일럿 노즐의 직경을 크게 하고 길이는 짧게 하는 것이 효과적인 유리화를 위해 유리할 것으로 예상되었다.

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Radial Variation of Anatomical Characteristics of Chestnut Wood (Castanea crenata) Grown in Korea - Vessel Element and Ray - (국내산 밤나무 목재의 해부학적 특성의 방사방향 변이성 - 도관요소 및 방사조직 -)

  • Lee, Seon-Hwa;Kwon, Sung-Min;Lee, Sung-Jae;Lee, Uk;Kim, Mahn-Jo;Kim, Nam-Hun
    • Journal of the Korean Wood Science and Technology
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    • v.37 no.1
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    • pp.19-28
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    • 2009
  • Some wood anatomical characteristics of seven chestnut cultivars (Tanzawa, Ibuki, Arima, Ginyose, Tsukuba, Riheiguri, and Mansung) grown in Korea were examined in this study. We investigated the radial variation of wood components such as diameter and number of earlywood vessel element and ray density in cross section and number and height of ray in tangential section. Discs were taken from the stem of seven chestnut cultivars at breath height and cut into the radial strip. Cross, radial, and tangential sections, 10 to $20{\mu}m$ thick, were sliced with a sliding microtome. These sections were stained, dehydrated, and mounted with Canada balsam according to common procedure. Measurement and observation were performed with a light microscopy. In all chestnut cultivars, radial and tangential diameter of vessel element increased but number of vessel element per $mm^2$ decreased with increasing tree age. Ray spacing (per mm) in cross section from pith to bark showed no significant variation, while number of ray per $mm^2$ increased but ray height decreased with the increase of tree age. Conclusively, the results obtained in present study were thought to be some valuable information for separating juvenile and adult wood as well as identifying chestnut cultivars.

An Experimental Study on the Effects of the Shape of a Drencher Head on the Characteristics of a Water Curtain (드렌처 헤드의 형상에 따른 수막특성에 관한 실험적 연구)

  • Lee, Seung-Chul;Kim, Bong-Jun;Lee, Jae-Ou;Park, Chung-Hwa;Hwang, Cheol-Hong
    • Fire Science and Engineering
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    • v.30 no.3
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    • pp.86-93
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    • 2016
  • The effects of the shape of a drencher head on the flow characteristics and radiation attenuation of a water curtain, in order to prevent a fire spread, were experimentally studied. The distance (h) between the orifice exit and deflector and the diameter of deflector (D) were varied as the shape factors of the head, with the same orifice diameter (d). It was found that an increase in h leads to an increase in the water flow rate and spray angle. However, the change in the spray angle decreases with increasing D. Increasing D brings about a subtle increase in the water flow rate and a significant decrease in the spray angle. A larger value of D makes it possible to produce a flatter pattern of the water curtain, but reduces the uniformity of the droplets inside the spray angle. The mean droplet diameter decreases significantly as the operating pressure increases. However, the variation in the shape of the drencher head does not significantly affect the change in the mean diameter at the same operating pressure. Finally, it was found that the radiation attenuation afforded by the water curtain at the same operating pressure was affected by water flow rate and droplet uniformity, which were determined by h and D, respectively.