• International Journal of Air-Conditioning and Refrigeration
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• 제13권2호
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• pp.61-70
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• 2005

This study treats the numerical analysis of performance and design for plume abatement wet/dry cooling tower with a dry type heat exchanger. A two-dimensional analysis is performed using the finite volume method for mechanical draft counterflow and crossflow tower. For a coupling problem between water and air system, a turbulent two phase flow is considered. The Effectiveness-NTU method is used for modeling of the dry type heat exchanger. The parametric simulations such as the relative flowrate of air and attachment length of an air mixer are performed to examine the effect on plume abatement. It is found that if the relative air flowrate ratio and the adequate air mixer type are chosen well in addition to the ratio of water to air flowrate, the loss of cooling capacity and the additional cost are reduced and the plume is abated.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.491-494
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• 2006

The output performance characteristics for surveyed sites were analyzed, using developed model. It consists of two main parts, the deciding flow duration characteristic of river and performance prediction model to estimate the output characteristics of small hydropower plants. As a result, it was found that the flowrate concerning with 25% of time ratio on flow duration curve can be selected to design flowrate of small hydropower plants, and the output characteristics of small hydropower plants having overflow dam are different from large scale hydropower plants.

• Korean Journal of Hydrosciences
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• 제3권
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• pp.81-96
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• 1992

This study represents the methodology for feasibility analysis of small hydro power SHP plant. Cumulative density function of Weibull distribution and Thiessen method were adopted to decide flow duration curve at SHP candidate site. The perfomance prediction model and construction cost estimation model for tunnel-type SHP plant were developed. Eight tunnel -type SHP candidate sites existing on Han-river were selected and surveyed for actual site reconnaissance. The performance characteristics and economical feasibility for these sites were analyzed by using developed models. As a result, it was found that the optimum design flowrate with the lowest unit generation cost for tunel-type SHP candidate site were the flowrate concerming with between 20% and 30% of time ratio on the flow duration curve. Additionally, primary design specifications such as design flowrate, effective head, capacity, annual averageload factor, annual electricity production were estimated and discussed for eight surveyed SHP candidate sites.

• 한국유체기계학회 논문집
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• 제7권5호
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• pp.7-12
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• 2004

Multi-path ultrasonic flowrate measuring technology is being received much attentions from a variety of industrial fields to exactly measure the flowrate. Multi-path ultrasonic flowmeter has much advantage since it has no moving parts and little pressure loss. It offers good accuracy, repeatability, linearity and turn-down ratio can be over 1:50. The present study investigates flowrate integration errors using weighting factors. A theoretical flow model uses power law to describe a fully developed velocity profiles and wall roughness is changed. Gaussian, Chebyshev, and Tailor methods are used to integrate line-average velocities. The obtained results show that Chebyshev method in 2, 4-path arrangement and Gaussian method in 3, 5-path arrangement are not affected for wall roughness changes.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.154-160
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• 2003

Multi-path ultrasonic flowrate measuring technology is being received much attentions from a variety of industrial fields to exactly measure the flowmeter. Multi-path ultrasonic flowmeter has much advantage since it has no moving parts and not occurred pressure loss. It offers good accuracy, repeatability, linearity and Tum-down ratio can measure over 1:50. The present study investigates flowrate integration errors using weighting factors. A theoretical flow model uses power law to describe a fully developed velocity profiles and wall roughness changes. The methods of weighting factor simulate three configurations of measuring location of gaussian, chebyshev and tailor method. The obtained results show that many chord arrangements are not affected for wall roughness changes and can measure accurate flowrate.

• 동력기계공학회지
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• 제4권3호
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• pp.25-33
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• 2000

This study represents three-dimensional turbulent flow characteristics around an axial fan measured at the operating point ${\varphi}=0.32$, which is equivalent to the maximum flowrate region, by using three-dimensional fiber-optic type LDA system. This LDA system is composed of a 5 W Argon-ion laser, two optics in back-scatter mode, three BSA's, a PC, and a three-dimensional automatic traversing system. A kind of paraffin fog is used for laser particles in this study. Mean velocity profiles around an axial fan along the downstream radial distance show that the streamwise and the tangential components exist as a predominant velocity and have the maximum value at the radial distance ratio 0.8, while the radial component has a small scale distribution and its flow direction is inward except a part of blade tip. The turbulent intensity profiles show that the radial component exists the most greatly. And also the turbulent kinetic energy shows about 60% as a maximum value at the radial distance ratio 0.9. Moreover, the Reynolds shear stresses do not exist at upstream flow, but the streamwise and the radial components of them show about 20% as a maximum value at the radial distance ratio 0.9 at downstream flow.

• Korean Chemical Engineering Research
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• 제47권5호
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• pp.630-638
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• 2009

생활폐기물 소각장에서 발생되는 질소산화물($NO_x$)을 저감을 위한 요소용액 이용 선택적 무촉매 환원(SNCR: selective non-catalytic reduction) 상용화 공정에 대하여 전산유체역학(CFD: computational fluid dynamics) 모델을 개발하였고, 이 모델은 현장 실험결과로 검증되었다. 저 농도 일산화탄소와 12% 과잉공기 조건에서 요소와 질소산화물간의 7개 화학반응식과 액적의 증발과정을 포함하는 3차원 난류반응 흐름 CFD 모델은 소각로에 설치된 SNCR 공정의 유체역학 모사를 위하여 사용하였다. 본 SNCR 공정에서는 정면 노즐 1개와 측면 노즐 2개를 사용하여 2차 연소로 내에 요소용액을 공기와 함께 분사하였다. 3개의 노즐에 동일유량으로 NSR=1.8에서 요소용액과 공기를 분사할 경우, 출구온도는 현장 실험값과 모사값이 일치하며, 질소산화물 저감효율은 실험에서는 57%, CFD 모사에서는 59%를 보여주었다. 각 노즐 별 분사유량의 비율을 변화하면서 수행된 CFD 모사 결과에서는 3개의 노즐에 동일 유량을 분사하는 것보다 정면 1개 노즐에 측면노즐 유량의 2배를 분사하는 것이 약 8% 높은 질소산화물저감 효율을 보여주었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.1008-1013
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• 2001

KSR-III propulsion system designed in KARI has a gas-pressurization system for propellant feeding system. This system uses a regulator for the control of the ullage pressure of propellant tank and a venturi for passive control of propellant flowrate. This system seems to be very reliable, but the flowrate of propellant varies according to the change of acceleration with the rocket flight. In this paper, dynamic characteristic of KSR-III propulsion feeding system was analyzed in flight condition. The purpose of this research is to find the variation of off ratio and propellant flowrate change for certification condition of engine reliability test.

• Biotechnology and Bioprocess Engineering:BBE
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• 제4권1호
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• pp.46-50
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• 1999

The application of pulsed electric field was investigated in the crossflow ultrafiltration of BSA (bovine serum albumn) to economize the application time of electric current as well as to avoid inherent problems of long-term application of electric field. During the application of various cyclic patterns of pulsed electric current, the averaged filtration flowrate and the degree of concentration were maintained higher than those obtained in the absence of electric current application. The temperature increase, pH change, and BSA loss by electrodeposition were all negligible during the operation. The averaged filtration flowrate increased as the ON/OFF duration ratio of electric current was higher and as the period of ON/OFF cycle was shorter. The re-establishment of concentration polarization was dependent to the duration of current OFF state and, therefore, a longer duration of OFF state was not favorable in maintaining higher filtration flow rate. Although the averaged filtration flowrate was enhanced as the magnitude of electric current increased, the flowrate enhancement became smaller as the magnitude of current value above which the degree of electrokinetic depolarization is no further improved.

• 대한환경공학회지
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• 제22권4호
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• pp.651-659
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• 2000

천연중화제의 스크러버 타입의 탈취장치에 의한 암모니아 제거반응 특성 및 중화반응에의 산화반응의 관여여부에 대하여 연구하였다. 중화제 희석비 및 유입유량, 공기유량, 암모니아 초기 농도를 운전인자로 선정하여 이들이 암모니아 제거효율에 미치는 영향을 살펴본 결과, 중화제 희석비는 1.0%, 중화제 유입유량은 $60m{\ell}/min$이 적절하고, 암모니아 초기농도 및 공기유량에 대해서는 loading rate를 함께 고려하면 제거효율에 큰 영향성은 나타내지 않았다. 암모니아의 중화반응에 산화반응의 관여여부를 살펴본 결과, 암모니아의 아질산염 및 질산염으로의 산화반응이 확인되었으며, 중화제량이 증가할수록 그 산화반응의 진행정도도 증가함을 확인하였다. 즉, 중화제에 의한 흡수현상과 함께 부분적으로 산화반응이 관여함을 확인하였다.