• 제목/요약/키워드: leakage rate

검색결과 934건 처리시간 0.033초

An Experimental Study on Air Leakage and Heat Transfer Characteristics of a Rotary-type Heat Recovery Ventilator

  • Han, Hwa-Taik;Kim, Min-Kyu
    • International Journal of Air-Conditioning and Refrigeration
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    • 제13권2호
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    • pp.83-88
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    • 2005
  • This study investigates the air leakage and heat transfer characteristics of a commercially available rotary-type air-to-air heat exchanger with a fiber polyester matrix. Crossover leakage between the exhaust and supply air is measured using a tracer gas method for various ventilation rates and rotational speeds of the wheel. A correlation equation for the leakage is obtained by summing up pressure leakage and carryover leakage. The pressure leakage is observed to be a function of ventilation rate only, and the carryover leakage is found to be a linear function of wheel speed. The real efficiency of the heat exchanger can be obtained from its apparent efficiency by taking into account the leakage ratio. The heat recovery efficiency decreases, as the ventilation rate increases. As the wheel speed increases, however, the efficiency increases initially but reaches a constant value for the speeds over 10rpm.

A new method fast measure cryogenic vessel heat leakage

  • LI, Zheng-Qing;LI, Xiao-Jin;LIU, Mo
    • 한국초전도ㆍ저온공학회논문지
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    • 제22권1호
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    • pp.24-28
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    • 2020
  • Heat leakage is an important parameter to reflect heat insulated performance of cryogenic vessel. According to the current standard requirements, it needs to measure the daily evaporation rate to indicate heat leakage. The test needs-over 24h after cryogenic vessel in heat equilibrium as standard required, therefore test efficiency is poor and new efficient method is required to cut test time. First of all, the volume of instantaneous evaporated gas and heat leakage are calculated by the current standard corresponding to the maximum allowable daily evaporation rate of cryogenic vessel. Depending on the relationship between real daily evaporation rate and maximum allowable daily evaporation rate of cryogenic vessel, we designed a new test method based on the pressure changes over time in cryogenic vessel to determine whether its heat insulated performance meets requirements or not. Secondly, the heat transfer process was analyzed in measurement of cryogenic vessel, and the heat transfer equations of whole system were established. Finally, the test was completed in four hours; meanwhile the heat leakage and daily evaporation rate of cryogenic vessel are calculated basing on test data.

격납건물 국부누설률시험 표준절차 개발 (Development of Standard Procedures for Local Leakage Rate Testing of Containment Vessel)

  • 문용식;김창수
    • 한국압력기기공학회 논문집
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    • 제8권2호
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    • pp.42-47
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    • 2012
  • The containment local leakage rate testing in nuclear power plants is performed in accordance with ANSI/ANS 56.8-1994 in Korea. Two methods, the make-up flow rate and the pressure decay, are used for local leakage rate testing. Though ANSI/ANS 56.8-1994 does not define clearly the minimum test duration for the make-up flow rate method, it requires obtaining the data after reaching the stable condition. Thus the prerequisite stable condition for data acquisition and the testing time is differently applied to each NPPs. Therefore, this study presents a standardized test procedure for data stabilization and testing time through experiments to improve the test reliability.

배급수관망에서의 누수복원량 산정방법 (Estimation method of natural rate of rise of leakage in water distribution system)

  • 진샘물;김경필;구자용
    • 상하수도학회지
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    • 제33권4호
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    • pp.299-309
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    • 2019
  • Waterworks facilities inevitably experience some amount of leakage even if there is a lot of investment or state-of-the-art technology that is applied such as DMA(District Metered Area) system construction, leakage detection, repair, pipe rehabilitation, etc. The primary reason is the leakage is naturally restored over time. In the UK, this restoration characteristic is defined as NRR(Natural rate of rise of leakage) and used to decision making for prioritizing active leakage control of DMAs. However, this restoration characteristic is well recognized, but researches on NRR in the water distribution system are insufficient in Korea. In this study, the estimation method of NRR was developed suitable for applicating in Korea considering of SCADA data, water infrastructure, and water usage patterns by modification of the UK's NRR method. The proposed method was applied to 9 DMAs and verified it's applicability by comparing with the other water loss performance indicators. It is expected that the proposed method can be used to support decision making for sustainable NRW(Nor-revenue water) management in the water distribution system.

Prediction of small-scale leak flow rate in LOCA situations using bidirectional GRU

  • Hye Seon Jo;Sang Hyun Lee;Man Gyun Na
    • Nuclear Engineering and Technology
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    • 제56권9호
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    • pp.3594-3601
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    • 2024
  • It is difficult to detect a small-scale leakage in a nuclear power plant (NPP) quickly and take appropriate action. Delaying these procedures can have adverse effects on NPPs. In this paper, we propose leak flow rate prediction using the bidirectional gated recurrent unit (Bi-GRU) method to detect leakage quickly and accurately in small-scale leakage situations because large-scale leak rates are known to be predicted accurately. The data were acquired by simulating small loss-of-coolant accidents (LOCA) or small-scale leakage situations using the modular accident analysis program (MAAP) code. In addition, to improve prediction performance, data were collected by distinguishing the break sizes in more detail. In addition, the prediction accuracy was improved by performing both LOCA diagnosis and leak flow rate prediction in small LOCA situations. The prediction model developed using the Bi-GRU showed a superior prediction performance compared with other artificial intelligence methods. Accordingly, the accurate and effective prediction model for small-scale leakage situations proposed herein is expected to support operators in decision-making and taking actions.

원전 안전주입 배관에서의 In-Leakage 에 의한 열성층 현상에 관한 연구 (A Study on Thermal Stratification Phenomenon due to In-Leakage in the Safety Injection Piping of Nuclear Power Plant)

  • 김광추;박만홍;염학기;김태룡;이선기
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.1633-1638
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    • 2003
  • In case that in-leakage through the valve disk occurs, a numerical study is performed to estimate on thermal stratification phenomenon in the Safety Injection piping connected with the Reactor Coolant System piping of Nuclear Power Plant. As the leakage flow rate increases, the temperature difference between top and bottom of horizontal piping has the inflection point. In the connection point of valve and piping, the maximum temperature difference between top and bottom was 185K and occurred in the condition of 10 times of standard leakage flow rate. In the connection point of elbow and horizontal piping, the maximum temperature difference was 145K and occurred in the condition of 15 times of standard leakage flow rate. In the vertical piping of Safety Injection piping, the near of connection point between elbow and vertical piping showed the outstanding thermal stratification phenomenon in comparison with another region because of turbulent penetration from Reactor Coolant System piping. In order to prevent damage of piping due to the thermal stratification when in-leakage through the valve disk occurs, the connection points between valve and piping, and the connection points between elbow and piping need to be inspected continually.

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파일럿형 공기압 방향제어 밸브의 누설 고장판정 기법에 관한 연구 (Leakage Failure Determination Method of Pilot Pneumatic Directional Control Valve)

  • 강보식;김경수;장무성
    • 한국신뢰성학회지:신뢰성응용연구
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    • 제14권4호
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    • pp.230-235
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    • 2014
  • The failure modes of pneumatic directional control valves include leakage, wear of the spool seal, and sticking of the spool. Among them, the main failure mode of the valve is leakage. The leakage is caused by the wear of the spool seal. However, due to the characteristics of the seal material, the leakage rate is fluctuated a lot rather than constantly increased over time. If life analysis is performed using the first time data of leakage failure, predicted life cycles can be different from the real life cycles. This paper predicts life cycles of the pilot pneumatic directional control valve based on the three point moving average which considers the average of the fluctuating leakage rate.

연료전지자동차의 고압수소저장시스템 수소 누출 안전성 평가 (The Evaluation of Hydrogen Leakage Safety for the High Pressure Hydrogen System of Fuel Cell Vehicle)

  • 김형기;최영민;김상현;심지현;황인철
    • 한국수소및신에너지학회논문집
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    • 제23권4호
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    • pp.316-322
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    • 2012
  • A fuel cell vehicle has the hydrogen detection sensors for checking the hydrogen leakage because it use hydrogen for its fuel and can't use a odorant to protect the fuel cell stack. To verify the hydrogen safety of leakage we select the high possible leak points of fittings in hydrogen storage system and test the leaking behavior at them. The hydrogen leakage flow rate is 10, 40, 118 NL/min and the criterion for maximum hydrogen leakage is based on allowing an equivalent release of combustion energy as permitted by gasoline vehicles in FMVSS301. There are total 18EA hydrogen leakage detection sensors installed in test system. we acquire the hydrogen leakage detection time and determine the ranking. Hydrogen leakage detection time decrease when hydrogen leakage flow rate increase. The minimum hydrogen leakage detection time is about 3 seconds when the flow rate is 118NL/min. In this study, we optimize hydrogen sensor position in fuel cell vehicle and verify the hydrogen leakage safety because there is no inflow inside the vehicle.

제습로터의 공기누설모델 개발 및 성능 특성에 관한 실험적 연구 (Experimental Study on Development of Air Leakage Model and Performance Characteristics of a Desiccant Rotor)

  • 강병하;피창헌;장영수
    • 대한기계학회논문집B
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    • 제36권1호
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    • pp.37-45
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    • 2012
  • 제습로터에서 발생하는 공기누설은 로터와 브러쉬 형태의 누설방지모 틈새의 양단 사이 차압에 의해 발생하는 압력누설이 지배적이며, 실험을 통해 압력누설특성을 파악하였다. 그 결과로, 압력누설량을 로터와 누설방지모의 틈새면적과 차압의 함수로 나타내었다. 위의 상관식을 바탕으로 제습로터의 공기누설모델을 개발하였으며, 실험을 통해 측정된 값과 위 모델을 바탕으로 계산된 값을 비교함으로써 공기누설모델을 검증하였다. 그리고 풍량에 따른 제습로터의 성능실험을 수행하였으며, 공기누설모델을 적용한 성능 분석을 통하여 실질적인 제습량과 공기누설량을 확인 하였다. 또한 동일한 제습로터가 적용된 제습냉방시스템을 고려하여 차압변화에 따른 공기누설의 영향을 공기누설모델을 이용하여 고찰하였다.

수치계산에 의한 축류터보기계의 유동장과 유동온실의 평가 III [회전차 익말단의 누설손실과 효율저하에 대한 평가] (Evaluation of Flowfield and Flow Losses insied Axial Turbomachinery Using Numerical Calculation [Evaluation of Tip Leakage Loss and Reduction of Efficiency by Tip Clearance])

  • 노수혁;조강래
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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    • pp.240-247
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    • 1998
  • Leakage vortices formed near blade tip causes an increase of total pressure loss near casing endwall region and as a result, the efficiency of rotor decreases. The reduction of rotor efficiency is related to the size of tip clearance. In this study, the three-dimensional flowfields in an axial flow rotor were calculated with varying tip clearance under various flow rates, and the numerical results were compared with experimental ones. The effects of tip clearance and attack angle on the leakage vortex and overall performance, and the less distributions were investigated through numerical calculations. In this study, tip leakage flow rate and total pressure loss by tip clearance were evaluated using numerical results and aprroximate equations were presented to evaluate the reduction of rotor efficiency by tip leakage flow.

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