• Title/Summary/Keyword: 경사각

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Experimental Investigation of Variations in Inclination Angle of Natural Convective Heat Sink with Plate Fins (플레이트-휜을 가지는 자연대류 히트싱트의 경사각 변화에 대한 실험적 연구)

  • Do, Kyu-Hyung;Kim, Tae-Hoon;Han, Yong-Shik;Choi, Byung-Il;Kim, Myung-Bae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.6
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    • pp.571-578
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    • 2012
  • In this paper, an experimental investigation is performed to estimate the thermal performance of a natural convective heat sink with plate fins subject to the uniform wall temperature condition. Extensive experiments are performed with various input powers, fin spacings, and heights of the natural convective heat sinks with plate fins. In particular, the effect of the inclination angle on the thermal performance of the heat sink is studied. In order to validate the experimental data, the experimental results are compared with results from previous studies. Based on the experimental results, the appropriate ranges of the previous correlations between the input power, the fin spacing, the fin height, and the inclination angle for the natural convective heat sink with plate fins are evaluated.

Analysis of force exerted on the nose by the spectacles weight (안경의 무게에 의해 코에 작용하는 힘 해석)

  • Kim, Dae-Soo
    • Journal of Korean Ophthalmic Optics Society
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    • v.10 no.4
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    • pp.273-281
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    • 2005
  • The weight of spectacles fined on is resolved into its components along the nose's slide plane and the normal to the nose plane where the nosepad is located. The equation and its numerical solution to determine the component force was derived as a function of splay angle ${\Psi}$, $sin{\Psi}$, $cos{\Psi}$, and $cot{\Psi}$, incorporated with ${\theta}$ and ${\Phi}$, the angles viewed from side and front of the face, respectively. Values of inclination angle ${\theta}$ and ${\Phi}$ could be obtained to fulfill the condition where the frictional force between the nose and pad is either greater than the normal pressure exerted by the spectacles on the nose. With the value of ${\theta}$ fixed the normal pressure increases as ${\Phi}$ increases. With ${\Phi}$ fixed, the effect of ${\theta}$ is the same.

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A Model Study on Deformability of A Transversely Isotropic Rock (평면이방성 암석의 변형특성 모델연구)

  • Park, Chul-Whan;Park, Eui-Seob;Park, Chan
    • Tunnel and Underground Space
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    • v.18 no.4
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    • pp.252-262
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    • 2008
  • In the uniaxial compressive test of a single specimen of transversely isotropic rock, its 5 independent elastic constants can not be defined since maximum 4 independent strain measurements are available theoretically. In order to solve this problem, one equation proposed by Saint Venant in 19C and confirmed by Lekhnitskii through the test experiences has been used for long time. Accordign to authors' experiences, however, this equation turned out to give erroneous elastic constants in some cases. Three new equations are suggested and their compatibilities are discussed in this paper. As the results of the analyses of the models, Lekhnitskii's suggested equation is effective for the specimen with the high dip angle whereas it results in the large erred output for that with dip angle less than $25{\sim}30$. It was found that the effectivenesses of three suggested equations and their compatibilities are subject to the dip angle and not to the amounts of elastic constants. Guide map to the selection of the compatible one of those suggested equations is presented as a result of the study.

Modeling of Hot-Coil/Cassette Dynamics and Design of Cassette Wedge Angle (핫코일-카세트 동역학 모델링 및 지지경사각 설계)

  • Hong, Sup;Hong, S.W.;Hong, S.Y.;Kim, H.J.;Kim, J.H.;Park, Y.M.
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.3
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    • pp.70-75
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    • 1997
  • This paper concerns with a safe and efficient transportation method of hot-coils on cargo ship. An automatic loading and unloading system of hot-coils by cassettes, which secure the geometrically unstable cargo, hot-coil, by supporting with wedges on both sides, is considered efficient and profitable. Safety of hot-coil on cassette and subsequently safety of total cargo ship are directly affected by the wedge angle of cassette. For optimal design of the cassette wedge angle, a dynamic model of hot-coil/cassette cargo is developed with constraint of no relative motions between the coil and the cassette. Force equilibrium conditions between resultant alternating inertia forces on hot-coil due to motions of cargo ship in waves and reactions forces from cassette wedge surfaces are derived and consequently a numerical simulation code is implemented. Cassette wedge angle of 37 degree is taken as optimal by considering dynamic stability of hot-coil and strength of cassette structure. Performance of the designed cassette wedge angle is investigated by scaled bench test.

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Study on Earth Pressure Acting Against Caisson Structure with the Heel (뒷굽이 있는 케이슨 안벽에 작용하는 토압에 대한 연구)

  • Yoo, Kun-Sun
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.29 no.2
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    • pp.67-76
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    • 2017
  • In this study, the effect of caisson heel on the active earth pressure is investigated. Using limit analysis method, inclinations of slip surface developed above the heel with different lengths are analyzed. The shorter the heel length, the larger those of inside slip surface, however those of outside slip surface are not changed. According to the relative heel length, relationships of internal friction angle of backfill material - wall friction angle between caisson structure and backfill - friction angle acting on virtual section at the end of heel are presented. Earth pressures acting against caisson structure with relatively short heel are smaller than Rankine earth pressure but always greater than Coulomb earth pressure which does not consider the heel length.

Performance Analysis on the Trapezoidal Fins having Different Slope for Enhanced Heat Exchange (열교환 향상을 위한 경사각이 다른 사다리꼴 휜에 대한 성능해석)

  • 강형석;윤세창
    • Journal of the Korean Society of Propulsion Engineers
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    • v.3 no.3
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    • pp.16-24
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    • 1999
  • Performance of the trapezoidal fins having different upper side slope is investigated by the three dimensional analytic method. It is shown that one equation can be used to analyse the trapezoidal fins having different upper side slope by adjusting the slope factor only. The performances for these fins are represented as a function of the non-dimensional fin length, fin width, Biot number and the slope factor when the remaining variables are fixed arbitrarily. One of the results is that the fin effectiveness increases as Biot number, the non-dimensional fin width and the slope factor decrease and as the non-dimensional fin length increases in the case of Bi $\leq$ 0.1 but the trend of the fin shape effect on the effectiveness is somewhat irregular for higher Biot number(i.e. Bi = 0.3).

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Development of Empirical Correlation to Calculate Pool Boiling Heat Transfer Coefficient on Inclined Tube Surface (경사진 튜브 표면의 풀비등 열전달계수 계산을 위한 실험식 개발)

  • Kang, Myeong-Gie
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.8
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    • pp.527-533
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    • 2016
  • A new empirical correlation was developed to identify the effect of an inclination angle on pool boiling heat transfer coefficient of a tube submerged in the saturated water at atmospheric pressure. Through the experiments and the survey of published results 431 data points were obtained and the nonlinear least square method was used as a regression technique. The heat flux of the tube($0{\sim}120kW/m^2$), inclination angle($0^{\circ}{\sim}90^{\circ}$), and the length divided by the diameter of a tube(18~42.52) were selected as major parameters. The newly developed correlation well predicts the experimental data within ${\pm}18%$, with some exceptions.

Heat Transfer Characteristics of Water Jet Impinging on Oblique Surface (경사면(傾斜面)에 충돌(衝突) 하는 수분류(水噴流)의 열전달(熱傳達) 특성(特性)에 관(關)한 연구(硏究))

  • Choi, Guk-Gwang;Na, Gi-Dae;Kim, Yeun-Young;Jeon, Sung-Taek;Lee, Jong-Su
    • Solar Energy
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    • v.13 no.1
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    • pp.1-10
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    • 1993
  • The purpose of this research is to investigate the characteristics of heat transfer in the downward axisymmetric free water jet system impinged on a flat oblique plate which has the uniform heat flux. Experimental conditions considered were Reynolds number, distance between nozzle and Bat plate, inclination angle of heater surface and nozzle exit velocity. Local Nusselt number was subjected to the influence of Re number, Pr number, oblique angle of heating surface and local position of flat plate. In the wall region of downward surface, The secondary peak point of heat transfer appeared at the local point of X/D=-8 from the stagnation point. The stagnation heat transfer rate of this experimental study augments 2.4 times than that of laminar theorical solution. The stagnation nusselt number is function of Reynolds number, nozzle-plate spacing Prandtl number and oblique angle of impinging plate.

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Effect of roof slope on the transmissivities of direct and diffuse solar radiation in multispan glasshouse by a computer simulation (컴퓨터 시뮬레이션에 의한 연동 유리온실내의 직달일사 및 산란일사 투과율에 미치는 지붕경사각의 영향)

  • 이석건;김용현
    • Journal of Bio-Environment Control
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    • v.7 no.4
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    • pp.324-329
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    • 1998
  • Effect of roof slope on the transmissivities of direct and diffuse solar radiation using a computer simulation model developed by Kim and Lee(1997) was analyzed for 10-span glasshouse located in Seoul(37$^{\circ}$34' N), Chonju(35$^{\circ}$49' N) and Cheju(33$^{\circ}$31' N). Transmissivities of diffuse solar radiation in glasshouse with roof slopes of 15, 20, 24.6, 30 and 35 degree were calculated as 61.3, 61.6, 61.7, 56.8 and 58.6%, respectively. Transmissivities of direct solar radiation(TDSR) during the period except summer season were highly affected by the roof slope. During the winter season, TDSR in glasshouse with roof slopes of 30 and 35 degree were higher than those with other roof slopes. Also, during the period except winter season, TDSR in glasshouse with roof slope of 20 degree were higher than those with other roof slopes. Difference in TDSR with latitude was significant during the period from October to February. At this period TDSR were highly appeared at lower latitude. Effect of roof slope on TDSR in S-N greenhouse was smaller than those in E-W greenhouse. It is considered that direct solar radiation highly transmitted in the glasshouse with roof slope of 20 degree.

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Effect of size and slope angle of tooth-shaped asperity on shear fracturing characteristics (삼각형 돌출부의 크기 및 경사각이 전단파괴 형상 특성에 미치는 영향)

  • Kim, Won-Keun;Choi, Woo-Yong;Park, Jong-Deok;Lee, Seok-Won
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.4
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    • pp.431-442
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    • 2013
  • Most of previous studies have insufficiently investigated the shear behavior and fracturing characteristics, experimentally in respect to the change of size of tooth-shaped surface asperity such as length and slope angle in a broad range. This study investigates the influence of the length and slope angle of a tooth-shaped surface asperity on the fracturing characteristics and the interface shear strength by using direct shear test apparatus. A total of 36 interface direct shear tests were conducted by changing the three types of slope angle of surface asperity, four type of length, and three types of normal stress. The shape of fractured surface after the test was quantified by using a three-dimensional surface roughness measurement apparatus. Through the experimental test results, the characteristics of fractured shape of surface asperity according to the normal stress were investigated. In addition, fractured length and height were quantified at each slope angle of surface asperity under a certain normal stress condition.