• Title/Summary/Keyword: 액체판

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Heat Transfer in Bubble Columns with High Viscous and Low Surface Tension Media (고점성 낮은표면장력 매체 기포탑에서 열전달)

  • Kim, Wan Tae;Lim, Dae Ho;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.52 no.4
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    • pp.516-521
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    • 2014
  • Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02~0.1 m/s), liquid viscosity ($0.1{\sim}0.3Pa{\cdot}s$) and surface tension ($66.1{\sim}72.9{\times}10^{-3}N/m$) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; $$h=2502U^{0.236}_{G}{\mu}^{-0.250}_{L}{\sigma}^{-0.028}_L$$ $$Nu=325Re^{0.180}Pr^{-0.067}We^{0.028}$$.

Characteristics of Bubble Flow Behavior in a Gas-liquid Countercurrent Bubble Column Bioreactor (기-액 향류 흐름 기포탑 생물 반응기에서 기포 흐름 거동 특성)

  • Son, Sung-Mo;Kang, Suk-Hwan;Lee, Chan-Gi;Jung, Sung-Hyun;Kang, Yong;Kim, Sang-Done
    • Korean Chemical Engineering Research
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    • v.43 no.2
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    • pp.272-277
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    • 2005
  • Characteristics of bubbling behavior and bubble properties were investigated in a gas-liquid countercurrent bubble column of in diameter 0.152 m and 3.5 m in height, respectively. Effects of gas and liquid velocities and bubble distribution mode(even, wall-side, central or asymmetric distribution) on the bubble properties such as chord length, frequency, rising velocity and holdup in the reactor were measured and examined by means of dual resistivity probe method. The bubble size, frequency and holdup increased with increasing gas($U_G$) or liquid velocity($U_L$). The rising velocity of bubbles increased with increasing $U_G$, whereas decreased with increasing $U_L$. The uniformity of bubble size distribution and bubble holdup decreased when the distribution mode of bubbles at the gas distributor was changed from even to wall-side, central or asymmetric. The central distribution of bubbles was better than asymmetric mode but worse than wall-side distribution, in considering the bubble holdup and uniformity of distribution.

Study of Cooling Performance Enhancement on Injector Face Plate of Rocket Engine (로켓엔진 분사면의 냉각성능 향상에 관한 연구)

  • Cho Won Kook;Seol Woo Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • v.y2005m4
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    • pp.215-218
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    • 2005
  • An optimal fuel manifold is suggested to improve the cooling performance of injector face plate. The cooling performance at the center area of the injector face plate is to be augmented while the spatial injection uniformity is maintained. The comparison of the cooling performance of 7 candidates gives the conclusion that the dividing plate from 2-3 injector row to 9-10 injector row is an optimal. The maximum face plate temperature decreases by $27\%$ while the injection uniformity is close to that of the original design. The pressure drop in the fuel manifold of the optimal design is also same as the original design.

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Cooling Performance Enhancement of a Rocket Engine Injector Face Plate (로켓엔진 분사면의 냉각성능 향상)

  • Cho Won Kook;Seol Woo Seok
    • Journal of the Korean Society of Propulsion Engineers
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    • v.9 no.3
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    • pp.92-100
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    • 2005
  • An optimal fuel manifold is suggested to improve the cooling performance of an injector face plate. The cooling performance at the center area of the injector face plate is to be augmented while the spatial injection uniformity is maintained. The comparison of the cooling performance of f candidates gives the conclusion that the dividing plate from 2-3 injector .ow to 9-10 injector. row is an optimal. The maximum face plate temperature decreases by 27$\%$ while the injection uniformity is close to that of the original design. The pressure drop in the fuel manifold of the optimal design is also same as the original design.

Numerical approach for comparative performance study of tube type and box type hybrid photovoltaic/thermal system (시뮬레이션을 통한 박스형과 튜브형 태양광열 복합 시스템의 성능 분석)

  • Bhattarai, Sujala;Kim, Dae-Hyun
    • Journal of the Korean Solar Energy Society
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    • v.31 no.5
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    • pp.9-18
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    • 2011
  • 태양광열 복합 시스템(photovoltaic/thermal hybrid solar system, PV/T)은 태양광 모듈 및 태양열 집열판의 단일화를 통한 전기 및 열에너지의 동시 생산이 가능하도록 구성되고 기존 태양광 모듈의 온도 상승에 따른 효율 저하의 문제점을 보완 및 발생하는 열을 회수하여 온수 생산이 가능한 장치이다. 본 연구에서는 액체형 PV/T 시스템의 대표적인 두 형태인 박스형과 튜브형의 성능 검증을 위하여 수학적 모델링을 통한 두 시스템의 열 및 전기적 성능을 비교 분석하였다. 모델링은 에너지 평형식을 이용하여 시간에 따른 각 부분의 온도의 변화를 예측할 수 있도록 수립되었으며 계산된 결과를 기준으로 전기, 열, 및 전체효율을 도출해 내고, 이를 바탕으로 두 시스템의 성능을 분석하였다. 시뮬레이션 결과를 바탕으로, 박스형 PV/T 시스템의 최고 온수 온도는 $52^{\circ}C$로 예측되었고, 반면에 튜브형은 $48^{\circ}C$에 머물렀다. 또한 열효율은 박스형이 최대 51%, 튜브형이 41%, 전기효율은 박스형이 약 14%, 그리고 튜브형이 13%로 나타났으며, 전체효율은 박스형이 73%, 그리고 튜브형이 64%로 나타나 박스형 PV/T 시스템이 튜브형보다 더 나은 성능을 가지는 것으로 예측되었다. 이는 박스형이 튜브형보다 태양광 모듈과 온수와의 접촉면적이 넓어 더 많은 열전달이 발생하기 때문으로 사료된다.

Response Surface Approach to Design Optimization of Regenerator Using Hot Air Heated by Solar Collector (태양열 온풍 이용을 위한 재생기의 설계 최적화 모델에 관한 연구)

  • Woo, Jong-Soo;Choi, Kwang-Hwan;Yoon, Jeong-In
    • Journal of the Korean Solar Energy Society
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    • v.23 no.3
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    • pp.7-14
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    • 2003
  • Absorption potential of desiccant solution significantly decreases after absorbing moisture from humid air, and a regeneration process requires a great amount of energy to recover absorption potential of desiccant solution. In an effort to develop an energy efficient regenerator, this study examines a regeneration process using hot air heated by solar radiation to recover absorption potential by evaporating moisture in liquid desiccant. More specifically, this study is aimed at finding the optimum operating condition of the regenerator by utilizing a well-established statistical tool, so-called response surface methodology(RSM), which may provide a functional relationship between independent and dependent variables. It is demonstrated that an optimization model to find the optimum operating condition can be obtained using the functional relationship between regeneration rate and affecting factors which is approximated on the basis experimental results.

Analysis on Heat Dissipation Characteristics of a Tile-Type Digital Transmitter/Receiver Module (적층형 디지털송수신모듈의 방열특성 분석)

  • Yoon, Kichul;Kim, Sangwoon;Heo, Jaehun;Kwak, Nojin;Kim, Chan Hong
    • Journal of the Korea Institute of Military Science and Technology
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    • v.22 no.2
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    • pp.249-254
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    • 2019
  • A Digital Transmitter/Receiver Module(DTRM), which is an essential part in active phased-array radar systems, generates a high heat density, and needs to be properly cooled for stable operation. A tile-type DTRM that is a stacking structure of multi-layer components was modeled with simplification and heat dissipation characteristics of the DTRM model were studied using computational fluid dynamics(CFD) simulations. Most of the heat was dissipated by the heat conduction through the cold plate, but the heat transfer by the forced convection on top of the DTRM also was found to play an important role in the thermal management. Under the given conjugated heat transfer environment, the DTRM was confirmed to secure a stable operating temperature range.

Numerical Formulation of Axisymmetric Shell Element and Its Application to Geotechnical Problems (축대칭 쉘 요소의 유한요소 수식화와 지반공학적 활용)

  • Shin, Hosung;Kim, Jin-Wook
    • Journal of the Korean Geotechnical Society
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    • v.36 no.12
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    • pp.27-34
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    • 2020
  • Use of axisymmetric shell element for the structure increases the efficiency and accuracy in finite element analysis of the interaction between the ground and the structure. This paper derived the force balance equation and the moment balance equation for an axisymmetric shell element based on Kirchhoff's theory. The governing equation for the axial deformation used the isoparametric shape function in the Galerkin formulation, and the governing equation for the shell bending used the higher-order shape function. The developed axisymmetric shell element was combined with Geo-COUS, a geotechnical finite element program for the coupled analysis with the ground. The accuracy of the developed element was confirmed through the example analyses of the circular plate and the liquid storage tank. And the energy balance equation for the axisymmetric shell element is presented.

An improved crystal rotation method for simultaneous measurement of pretilt angle and thickness of a liquid crystal layer (액정셀의 선경사각과 액정층의 두께를 함께 재는 개선된 결정회전법)

  • Son, Gong-Sook;Park, Chan;Park, Hee-Gap;Kim, Jin-Seung;Rho, Bong-Gyu;Lee, Hyong-Jong;Kim, Jae-Ki
    • Korean Journal of Optics and Photonics
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    • v.7 no.3
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    • pp.213-218
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    • 1996
  • An improved crystal rotation method with increased accuracy and range is proposed and experimentally verified for simultaneous measurement of molecular tilt angle and thickness of LC (liquid crystal) layer of an LC cell. The improvement is brought about by direct determination of difference between phases instead of intensities of two components of orthogonal linear polarization of the light passing through an LC cell filled with uniformly oriented molecules. By comparing the experimental data with theoretical result the thickness and pretilt angle are determined more precisely. Further improvement is brought about by use of a liquid gate filled with an index matching liquid in which the LC cell is immersed. Because of the index matching liquid reflection of light at the surfaces of an LC cell almost completely disappears and the range of angle of refraction in the LC layer increases significantly, which gives rise to increased signal to noise ration as well as decreased statistical error. With this improvement precise measurement for either very thin (<10 ${\mu}{\textrm}{m}$) and/or higher pretilt angle($\geq$10$^{\circ}$) LC cells become possible.

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Effect of Construction Joint on Leakage Resistance of Gas in Reinforced Concrete Pressure Vessels (철근콘크리트 압력용기에서 시공이음이 가스의 누설저항에 미치는 영향)

  • Yi, Seong-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.2
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    • pp.87-94
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    • 2017
  • In the nuclear power plant, the steel or polymer liner plates are adopted to prohibit the inner concrete surface from contacting with gas or liquid materials. If there is an accident, the plate may be damaged, and, in this case, concrete shall have the final responsibility to safety requirements. In this paper, an experimental research was carried out to investigate the effects of construction joint and wet and loading conditions on the permeability of concrete. The test results showed that, under a construction joint in the wet condition, leakage of gas pressure has been started from $1kg/cm^2$. However, when there are no construction joints, it is initiated from $2kg/cm^2$. In addition, under the air dried and unloading condition, regardless of with or without the presence of the construction joint, since the gas passage that exist in concrete is constant, leakage has a constant tendency to increase. Finally, under the loading condition, as described in Reference 1, since leakage is inversely proportional to the thickness of the wall, and, considering the wall thickness of the actual plant, it is found that there will not be no problem in the sealing of the gas.