• 에너지공학
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• 제14권1호
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• pp.62-71
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• 2005

B&C(Blowdown and Condensation)장치를 이용하여 APR1400 실규모 I-Sparger의 증기제트 응축에 의한 수조내 열혼합 현상에 대한 실험이 수행되었다. 한정된 가압기 용량으로 인하여 과도상태 실험이 수행되었으며, 실험을 통해 수조내에 배치된 열전대를 사용하여 열혼합 자료를 얻었다. 측정된 열혼합 자료를 바탕으로 지역별 온도 변화의 경향과 수조 수직-단면상의 온도 윤곽도를 작성하였으며 이를 바탕으로 I-Sparger의 열혼합 특성을 파악하였다. 실험결과에서 I-Sparger에 의한 열혼합 특성은 I-Sparger 설계특성이 나타나는 열혼합 경향을 보이고 있음을 확인하였다.

• Journal of Plant Biotechnology
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• 제32권2호
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• pp.111-116
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• 2005

생물반응기 배양을 통하여 인삼 부정근을 대량생산하고자 할 때, 가장 이상적인 공기주입량의 조절은 배양초기부터 말기까지 각각의 농도 (0.05, 0.1, 0.2, 0.3 vvm)를 가지고 동일하게 주입하는 방법보다는 인삼 부정근의 생장이 증가함에 따라 공기주입량을 약 10일 간격을 두고 $0.05{\sim}0.3\;vvm$으로 서서히 증가시키는 것이 인삼 부정근의 생장(175.8 g dry wt)과 총 ginsenoside 함량 (4.3 mg/g dry wt)을 최대로 증가시켰다. 또한 생물반응기내 sparger의 다공 크기를 15, 30, $60\;{\mu}m$으로 각각 제작하여 배양하였을 경우, 인삼 부정근의 생장은 $15\;{\mu}m$ sparger (175.9 g dry wt)에서 양호하였으나 총 ginsenoside 함량은 $60\;{\mu}m$ sparger (4.9 mg/g dry wt)에서 우수하게 나타났다. 마지막으로 sparger의 직경을 1.5, 3.0, 5.0, 8.0 cm로 각각 제작하여 배양하였을 때 (공기주입량은 $0.05{\sim}0.3$ vvm, sparger의 다공크기는 $15\;{\mu}m$로 채택), 8.0 cm sparger에서 인삼 부정근의 생장(191.9 g dry wt)과 총 ginsenoside 함량 (4.9 mg/g dry wt)이 다른 처리구에 비하여 가장 우수하게 나타났다.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1390-1398
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• 1999

A numerical analysis for ROT sparger of PWR(Pressurized Water Reactor) is carried out. Computation is performed to investigate the flow characteristics as the change of design factor. As the result of this study, RDT sparger's flow resistance coefficient is K=3.53 at the present design condition if engineering mar&in is considered with 20%, and flow ratio into branch pipe is $Q_s/Q_i=0.41$. Velocity distribution at exit is not uniform because of separation in branch pipe. In the change of inlet flow rate and section area ratio of branch pipe for main pipe, flow resistance coefficient is increased as $Q_s/Q_i$ decreasing, but in the change of branch angle and outlet nozzle diameter of main pipe, flow resistance coefficient is decreased as $Q_s/Q_i$ decreasing. As the change rate of $Q_s/Q_i$ is the larger, the change rate of flow resistance coefficient is the larger. The change rate of pressure loss is the largest change as section area ratio changing. The optimal design condition of sparger is estimated as the outlet nozzle diameter ratio of main pipe is $D_s/D_i=0.333$, the section area ratio is $A_s/A_i=0.2$ and the branch angle is ${\alpha}=55^{\circ}$.

• 설비공학논문집
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• 제13권5호
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• pp.356-367
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• 2001

A numerical analysis on branch type sparger in drain tank for depressurization is performed to investigate the flow characteristics due to the change of design factor. As the result of this study, sparger\\`s flow resistance coefficient(K) is 3.53 at the present design condition when engineering margin for surface roughness is considered as 20%, and flow ratio into branch pipe ($Q_s/Q_i$) is 0.41. The correlation for calculating flow resistance coefficients as design factor is presented. Flow resistance coefficient is increased as section area ratio of branch pipe for main pipe and outlet nozzle diameter of main pipe decreasing, but the effects of branch angle and inlet flow rate of main pipe are small. As the change rate of ($Q_s/Q_i$)becomes larger, the change rate of flow resistance coefficient increases. The rate of pressure loss has the largest change as section area ratio changing. The condition of maximum flow resistance in sparger is when the outlet nozzle diameter ratio of main pipe ($D_e/D_i$) is 0.167, the section area ratio ($A_s/A_i$) is 0.1 and the branch angle ($\alpha$) is 55^{\circ}$.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.137.2-137
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• 2001

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.780-791
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• 2023

To study oscillation characteristic of steam and non-condensable gas direct contact condensation through multi-hole sparger at low mass flux, a series of experiments of pure steam and mixture gas condensation have been carried out under the conditions of steam mass flux of 20-120kg/m²s, water temperature of 20-95 ℃ and mass fraction of non-condensable gas of 0-5%. The regime map of pure steam condensation through multi-hole sparger is divided into steam chugging, separated bubble, aggregated bubble and escaping aggregated bubble. The bubbles behavior of synchronization in the same hole columns and desynchronized excitation between different hole columns can be found. The coalescence effect of mixture bubbles increases with water temperature and non-condensable gas content increasing. Pressure oscillation intensity of pure steam condensation first increases and then decreases with water temperature increasing, and increases with steam mass flux increasing. Pressure oscillation intensity of mixture gas condensation decreases with water temperature and non-condensable gas content increasing, which is significantly weaker than that of pure steam condensation. The oscillation dominant frequency decreases with the rise of water temperature and non-condensable gas content. The correlations for oscillation intensity and dominant frequency respectively are developed in pure steam and mixture gas condensation at low mass flux.

• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.482-491
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• 2001

An experimental study has been carried out to investigate an I-type sparger-performance in view of pressure oscillation and thermal mixing in a pool. Its pitch-to-hole diameter, P/D, varies from 2 to 5. The test conditions are restricted to the condensation oscillation regime. In the present study, two different hole patterns, staggered and parallel types, are employed under various test conditions. The amplitude of the pressure pulse shows a peak for pool temperatures of 45∼85$\^{C}$, which depends on P/D and the steam mass flux. The effect of hole pattern on the pressure load is smaller than that of P/D. The dominant frequency increases with the subcooling temperature of pool water and P/D. A correlation for the dominant frequency is proposed in terms of the pitch-to-hole diameter ratio and other dimensionless thermal hydraulic parameters.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.813-820
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• 2001

The Safety depressurization System(SDS) of KNGR prevents RCS from overpressurization by discharging high pressure and temperature coolant through the I-sparger into the IRWST during an accident. If IRWST water temperature rise locally, around the sparger, beyond $200_{\circ}$2000 F by the discharged coolant, unstable steam condensation can cause large pressure load on the IRWST wall. To investigate whether this condition can be avoided for the design basis event IOPOSRV(Inadvertent Opening of one Pilot Operated Safety Relief Valve), the flow and temperature distribution of water in the IRWST is calculated by using CFX 4.3 computational fluid dynamic code. According to the results, since pool water temperature does not exceeds temperature limit within 50 seconds after the opening of one POSRV, it can be assured that the integrity of IRWST wall is maintained.

• Nuclear Engineering and Technology
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• 제36권4호
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• pp.285-294
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• 2004

Pressure wave propagation in the discharge piping with a sparger submerged in a water pool, following the opening of a safety relief valve, is analyzed. To predict the pressure transient behavior, a RELAP5/MOD3 code is used. The applicability of the RELAP5 code and the adequacy of the present modeling scheme are confirmed by simulating the applicable experiment on a water hammer with voiding. As a base case, the modeling scheme was used to calculate the wave propagation inside a vertical pipe with sparger holes and submerged within a water pool. In addition, the effects on wave propagation of geometric factors, such as the loss coefficient, the pipe configuration, and the subdivision of sparger pipe, are investigated. The effects of inflow conditions, such as water slug inflow and the slow opening of a safety relief valve are also examined.

• 에너지공학
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• 제11권3호
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• pp.237-246
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• 2002

한국형차세대원자로 APR-1400의 안전감압계통이 작동하면 물, 공기 및 증기가 sparger를 통해 격납건물 내 핵연료재장전 수조로 차례로 방출된다. 방출 과정 중 생기는 여러 현상 중에서 수조 내의 공기 기포군은 저주파, 고진폭의 진동 하중을 발생하며, 주파수가 침수 구조물의 고유 주파수와 거의 같은 경우에는 구조물에 심각한 영향을 줄 수 있다. 이러한 현상은 복잡하기 때문에 주파수와 하중에 대한 규명은 주로 실험에 의존해 왔으며 수치해석적 연구는 이루어지지 않았다. 본 연구에서는 sparger를 통해 수조 내로 방출되는 공기 기포군의 거동에 대한 수치해석을 상용 열수력 해석 코드인 FLUENT Version 4.5를 사용하여 수행하였다. 다상유동 해석모델중 VOF(Volume Of Fluid)모델을 사용하여 물, 공기 및 증기 등의 다상유동을 모의하였다. 해석결과를 sparger 개발을 위해 ABB-Atom이 수행하였던 실험결과와 비교하여 만족할만한 결과를 얻었다.