• Nuclear Engineering and Technology
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• 제31권6호
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• pp.548-560
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• 1999

An experimental investigation has been peformed to examine the effects of various geometrical parameters and an initial operating condition on the air-water countercurrent How limitation (CCFL) in a simulated PWR hot leg. A total of 118 experimental data for the onset of CCFL and zero liquid penetration were obtained for various combinations of test parameters. It was observe that the CCFL can be classified into three different categories: (the onset of CCFL, (the partial liquid delivery, and (r) the zero liquid penetration. The observed mechanisms of the onset of CCFL were different depending on the inlet water flow rate. The parametric effects of pipe diameter, horizontal pipe length, horizontal pipe length-to-diameter (L/D) ratio, and initial water level in the horizontal pipe of the test section on the onset of air-water CCFL were also examined. An empirical correlation for the onset of CCFL in a horizontal pipe connected to an inclined riser was developed in terms of Wallis flooding parameters for the low inlet water flow rate region. Comparisons of the present empirical correlation with the air-water CCFL data of large pipe diameters show that the present correlation agrees more closely with the experimental data than the existing CCFL correlations.

• 설비공학논문집
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• 제10권5호
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• pp.619-629
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• 1998

An experimental work was conducted to investigate a feasibility of simultaneous measurement of gas-liquid two-phase flowrates with double orifice plates using air and water. The tests were carried out under the atmospheric pressure and at the ambient temperature using two different tube sizes. Qualities of an air-water flow in the present study have values less than 0.1 and thus the mixed flow showed bubbly, plug, slug flow regimes. The probability density function (PDF) and the power spectral density function (PSDF) of the instantaneous pressure drop traces for the flow regimes were obtained. It is found that some distinctive features exist in the distribution of these functions, depending upon the two-phase flow pattern. The time-averaged value of the instantaneous pressure drop increases with increasing gas and liquid flowrates, showing a single-valued function for the total mass flowrate and the quality. It is also found that the two-phase discharge coefficient exhibits a consistent trend for variation of dimensionless parameters such as the superficial velocity ratio and the gas Reynolds number. The results indicate that simultaneous measurement of two-phase flowrate may be possible based upon a statistical analysis of the instantaneous pressure drop curves monitored using double orifice plates.

• 설비공학논문집
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• 제1권2호
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• pp.190-201
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• 1989

This experimental investigation has been conducted to determine the effects of swirling angle and flow patterns on distributions of void fraction, bubble velocity and two-phase pressure drop in a vertical straight tube. Swirling angles of $0^{\circ}$ (non swirling), $30^{\circ}$, and $45^{\circ}$ were tested with air-water two components over a range of superficial air velocities. A transparent lucite tube of 38mm in internal diameter was used for the test section. The void fraction and bubble velocities were measured by means of a optical fiber probe at the upper part of the swirler in the test section. Pressure drops which seem to be closely related with flow patterns and swirling angle were measured by a differential pressure transducer. It is shown that the probability density functions of pressure drop demonstrate peculiar features for both swirling angles and flow patterns, whereas the distributions of void fraction and bubble velocities are parabolic and flat shape in the vicinity of tube center, respectively except bubbly flow in any swirling angle cases, and the void fraction increases with increasing swirling angle around the center of tube.

• 에너지공학
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• 제21권1호
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• pp.43-46
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• 2012

A fluidized bed drying approach was utilized to the synthesis of water glass based silica aerogel powders. The effects of the fluidized bed drying conditions such as the superficial velocity and temperature of hot air and bead size as well as bead/wet-gel ratio, on the physical properties such as tapping density and productivity of the aerogel powders were systematically investigated. The experimental results showed that the amount of beads mixed with wet-gels in the fluidized bed column has the most profound impact on the fluidization efficiency, greatly enhancing the yield of the aerogel powders up to 98% with a proper bead/wet-gel weight ratio as compared to 72% without using beads. No significant change was observed in the tapping density over a wide range of the fluidized drying condition. Consequently the fluidized bed drying approach shows a good promise as an alternative route for the large-scale production of the aerogel powders.

• Journal of Advanced Marine Engineering and Technology
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• 제28권2호
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• pp.338-346
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• 2004

Experimental data on the effect of the variable gravity magnitude, namely microgravity, normal gravity and hyper-gravity, on flow pattern and frictional pressure drop were obtained during co-current air-water flow in a horizontal tube, The flow patterns were found to depend strongly on the gravity magnitude and certain flow pattern were found to depend on the gas superficial velocity. The effect of the gravity magnitude had an effect on the frictional pressure drop only at low flow rates. The present data are used to evaluate some of existing flow pattern transition and pressure drop models and correlations.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2002년도 생물공학의 동향 (X)
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• pp.515-518
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• 2002

The method of foam fractionation can be applied to enrich proteins from a dilute protein solution if the proteins are hydrophobic and foam. If a protein, such as invertase, is hydrophilic, a dilute solution containing this protein may not foam. In that case, a batch foam fractionation process may not be appropriate for recovering a concentrated solution of that protein. In this paper, various concentrations of invertase were added to a dilute solution containing bromelain (a hydrophobic protein), in order to determine how the presence of a hydrophilic protein can affect the recovery of the desired hydrophobic protein. The effect of invertase on bromelain recovery was studied here at an initial bulk solution pH of 5 and an air superficial velocity of 4.6 cm/s.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.371-373
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• 2003

해수 중 초기 단백질 농도가 증가할수록 준정상상태에 도달하는 시간이 길어졌으며 최대 포말생성 높이는 증가하였다. 공기분산기의 기공크기가 작을수록 포말생성 높이는 증가하였으나 G3, G4, 산기석에서는 포말생성 높이가 거의 비슷하게 나타났다. 공탑공기유속이 증가할수록 포말생성 높이는 증가하였으며 운전시 안정적인 기포생성을 위해서 공탑공기유속을 0.7-0.8 cm/sec 로 하는 것이 보다 좋을 것으로 생각된다. 최적 pH 조건은 5-8의 약산과 약염기 부근이었으며 해수에서 $NaHCO_3$ 농도에 따른 포말생성 높이의 변화는 거의 없는 것으로 나타났는데 이는 해수 중 NaCl의 영향 때문이라고 생각된다.

• 설비공학논문집
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• 제27권10호
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• pp.520-526
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• 2015

The characteristics of gas-liquid Taylor (Slug) flow in a square micro-channel of $600{\sim}600{{\mu}m}$ were investigated experimentally in this paper. The test fluids were nitrogen and water. The liquid and gas superficial velocities were 0.01~3 m/s and 0.1~3 m/s, respectively. Bubble and liquid slug length, bubble velocity, and frequency were measured by analyzing optical images using a high speed camera. Bubble length decreased with higher liquid flow rate, which increased dramatically with higher gas flow rate. However, slug length did not vary with changes in inlet liquid conditions. Additionally, bubble velocities and frequencies increased with higher liquid and gas flow rates. It was found that measured bubble lengths were in good agreement with the empirical models in the existing literature, but slug lengths were not.

• Korean Chemical Engineering Research
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• 제55권6호
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• pp.846-853
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• 2017

순환유동층 모사장치와 $30kW_{th}$급 파일럿 연소기를 활용하여 슬러지 순산소 유동층 연소특성을 살펴보았다. 순환유동층 모사실험에서 최소유동화속도($U_{mf}$)는 0.120 m/s로 계산되었고, 고속유동화를 위한 공탑속도는 2.5 m/s 이상으로 결정되었다. 파일럿 연소실험에서는 일반공기 및 21~40% 순산소 연소실험이 수행되었다. 배출가스 온도의 경우 21~25% 순산소 연소가 일반공기 및 30% 이상의 순산소 연소보다 상대적으로 높았다. 또한, 배출가스 중 $CO_2$ 배출농도가 21~25% 순산소 연소 범위에서 80% 이상으로 나타났다. 이를 고려한 전반적인 연소특성을 살펴 보았을 때 25% 순산소 연소가 본 슬러지 연료 연소에 대한 장시간 운전에 있어 보다 적합한 것으로 사료된다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.24-32
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• 2004

The characteristics of heat transfer from horizontal cylinder immersed in both a riser and downcomer of a circulating fluidized beds were investigated experimentally under different values of solids mass flux, superficial air velocity, particle size diameter, and different bed materials. The test results indicated that local heat transfer coefficients in both riser and downcomer are strongly influenced by angular position, and mass flux, as well as by particle size and bed materials. The local heat transfer coefficients around a circumference of the cylinder inside a riser and downcomer of a CFB exhibited a general tendency to increase with decreasing particle size and increasing solids mass flux and vary with different bed materials. Also the averaged heat transfer coefficient calculated from local heat transfer coefficient exhibited the same trend as a local i.e increase with decrease particle size and increasing solids mass flux and vary with varying bed materials. The general trend for a riser local heat transfer coefficient is decrease with increase angle until ${\Phi}$ = 0.5-0.6 (Where at angle =180$^{\circ}$ ${\Phi}$ =1). Also the general trend for a local heat transfer coefficient in downcomer is to increase with increase the angle until ${\Phi}$= ${\theta}/{\Pi}$ = 0.3-0.5 (Where at angle =180$^{\circ}$ ${\Phi}$ =1). Comparison the results of the heat transfer in the riser and downcomer of a circulating fluidized beds shows that they have approximately the same trend but the values of heat transfer coefficients in riser is higher than in downcomer.