• Title, Summary, Keyword: internal pressure

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Study on the Quantitative Rod Internal Pressure Design Criterion (정량적인 핵연료봉 내압 설계기준에 관한 연구)

  • Kim, Kyu-Tae;Kim, Oh-Hwan;Han, Hee-Tak
    • Nuclear Engineering and Technology
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    • v.23 no.4
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    • pp.363-373
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    • 1991
  • The current rod internal pressure criterion permits fuel rods to operate with internal pressures in excess of system pressure only if internal overpressure does not cause the diametral gap enlargement. In this study, the generic allowable internal gas pressure not violating this criterion is estimated as a function of rod power. The results show that the generic allowable internal gas pressure decreases linearly with the increase of rod power. Application of the generic allowable internal gas pressure for the rod internal pressure design criterion will result in the simplication of the current design procedure for checking the diametral gap enlargement caused by internal overpressure because according to the current design procedure the cladding creepout rate should be compared with the fuel swelling rate at each axial node at each time step whenever internal pressure exceeds the system pressure.

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Correlation of internal and external pressures and net pressure factors for cladding design

  • Bodhinayake, Geeth G.;Ginger, John D.;Henderson, David J.
    • Wind and Structures
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    • v.30 no.3
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    • pp.219-229
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    • 2020
  • Net pressures on roofs and walls of buildings are dependent on the internal and external pressure fluctuations. The variation of internal and external pressures are influenced by the size and location of the openings. The correlation of external and internal pressure influences the net pressures acting on cladding on different parts of the roof and walls. The peak internal and peak external pressures do not occur simultaneously, therefore, a reduction can be applied to the peak internal and external pressures to obtain a peak net pressure for cladding design. A 1:200 scale wind tunnel model study was conducted to determine the correlations of external and internal pressures and effective reduction to net pressures (i.e., net pressure factors, FC) for roof and wall cladding. The results show that external and internal pressures on the windward roof and wall edges are well correlated. The largest ${\mathcal{C}}_{{\check{p},net}$, highest correlation coefficient and the highest FC are obtained for different wind directions within 90° ≤ θ ≤ 135°, where the large openings are on the windward wall. The study also gives net pressure factors FC for areas on the roof and wall cladding for nominally sealed buildings and the buildings with a large windward wall opening. These factors indicate that a 5% to 10% reduction to the action combination factor, KC specified in AS/NZS 1170.2(2011) is possible for some critical design scenarios.

Effect of building volume and opening size on fluctuating internal pressures

  • Ginger, John D.;Holmes, John D.;Kopp, Gregory A.
    • Wind and Structures
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    • v.11 no.5
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    • pp.361-376
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    • 2008
  • This paper considers internal pressure fluctuations for a range of building volumes and dominant wall opening areas. The study recognizes that the air flow in and out of the dominant opening in the envelope generates Helmholtz resonance, which can amplify the internal pressure fluctuations compared to the external pressure, at the opening. Numerical methods were used to estimate fluctuating standard deviation and peak (i.e. design) internal pressures from full-scale measured external pressures. The ratios of standard deviation and peak internal pressures to the external pressures at a dominant windward wall opening of area, AW are presented in terms of the non-dimensional opening size to volume parameter, $S^*=(a_s/\bar{U}_h)^2(A_W^{3/2}/V_{Ie})$ where $a_s$ is the speed of sound, $\bar{U}_h$ is the mean wind speed at the top of the building and $V_{Ie}$ is the effective internal volume. The standard deviation of internal pressure exceeds the external pressures at the opening, for $S^*$ greater than about 0.75, showing increasing amplification with increasing $S^*$. The peak internal pressure can be expected to exceed the peak external pressure at the opening by 10% to 50%, for $S^*$ greater than about 5. A dominant leeward wall opening also produces similar fluctuating internal pressure characteristics.

Internal pressures in buildings with a dominant opening and background porosity

  • Kim, P.Y.;Ginger, J.D.
    • Wind and Structures
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    • v.16 no.1
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    • pp.47-60
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    • 2013
  • A dominant opening in a windward wall, which generates large internal pressures in a building, is a critical structural design criterion. The internal pressure fluctuations are a function of the dominant opening area size, internal volume size and external pressure at the opening. In addition, many buildings have background leakage, which can attenuate internal pressure fluctuations. This study examines internal pressure in buildings for a range of dominant opening areas, internal volume sizes and background porosities. The effects of background porosity are incorporated into the governing equation. The ratio of the background leakage area $A_L$ to dominant opening area $A_W$ is presented in a non-dimensional format through a parameter, ${\phi}_6-A_L/A_W$. Background porosity was found to attenuate the internal pressure fluctuations when ${\phi}_6$ is larger than 0.2. The dominant opening discharge coefficient, ${\kappa}$ was estimated to lie between 0.05 to 0.40 and the effective background porosity discharge coefficient ${\kappa}^{\prime}_L$, was estimated to be between 0.05 to 0.50.

Characteristic of Wind Pressure Distribution on the Roof of Hyperbolic Paraboloid Spatial Structures (쌍곡선포물선 대공간 구조물의 측벽개구율에 따른 지붕의 풍압특성)

  • You, Jang-Youl;You, Ki-Pyo
    • Journal of the Korean Association for Spatial Structures
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    • v.13 no.1
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    • pp.51-57
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    • 2013
  • There can be diverse causes in the destruction of a large space structure by strong wind such as characteristics of construction materials and changes in internal and external wind pressure of the structure. To evaluate the wind pressure of roof against the large space structure, wind pressure experiment is performed. However, in this wind pressure experiment, peak internal pressure coefficient is set according to the opening of the roof in Korea wind code. In this article, it was tried to identify the change of internal pressure coefficient and the characteristics of wind pressure coefficient acting on the roof by two kinds of opening on the side of the structure with Hyperbolic Paraboloid Spatial Structures roof. When analyzing internal pressure coefficient according to roof shape, it was found that minimum (52%) and maximum (30%~80%) overestimation was made comparing to partial opening type proposed in the current wind load. It is judged that evaluation according to the opening rate of the structure should be made to evaluate the internal pressure coefficient according to load.

Simple Modeling of Plastic Layer in Coke Oven for Internal Gas Pressure (단순 연화층 모델을 적용한 석탄 성상별 Coke Oven 내의 가스압 특성)

  • Park, Ju-Hyun;Choi, Sang-Min
    • 한국연소학회:학술대회논문집
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    • pp.36-41
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    • 2006
  • A simplified model of plastic layer and internal gas pressure In a coke oven is presented. We calculate internal gas pressure using presented model. And results are compared with calculated results using experimental data. Results show the difference of internal gas pressure by coal composition. The model is used to show that the permeability at the resolidification end of the plastic layer is a key determinant of the magnitude of the internal gas pressure.

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A Method to Monitor Vacuum Degree Using Capacitive Partial Discharge Coupler

  • Sun, Jong-Ho;Youn, Young-Woo;Hwang, Don-Ha;Yi, Sang-Hwa;Kang, Dong-Sik
    • Journal of Electrical Engineering and Technology
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    • v.7 no.6
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    • pp.959-964
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    • 2012
  • Internal pressure of vacuum interrupter (VI) is one of the most important parameters in VI operation and may increase due to the outgassing from the materials inside VI or gas permeation through metal flange or ceramic vessel. The increase of the pressure above a certain level leads to the failures of switching or insulation. Therefore, an effective pressure check of VI is essential and an analysis of partial discharge (PD) characteristics is an effective monitoring method to identify the degree of the internal pressure of VI. This paper introduces a research work on monitoring the internal pressure of VI by analyzing PDs which were measured using a capacitive PD coupler. The authors have developed cost effective capacitive coupler based on the ceramic material that has an excellent insulation properties and the main component of the capacitive coupler is made by SrTiO3. Detectable internal pressure range and distinguishability of the internal pressure of VI were investigated. From the PD tests results, the internal pressure range, from $10^{-2}$ torr to 500 torr, can be monitored by PD measurements using the capacitive coupler and PD inception voltage (PDIV) follows the Paschen's law. In addition, rise time of PD pulse at 13.2kV decreases with the increase of the internal pressure of VI.

Internal pressure dynamics of a leaky and quasi-statically flexible building with a dominant opening

  • Guha, T.K.;Sharma, R.N.;Richards, P.J.
    • Wind and Structures
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    • v.16 no.1
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    • pp.61-91
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    • 2013
  • An analytical model of internal pressure response of a leaky and quasi-statically flexible building with a dominant opening is provided by including the effect of the envelope external pressure fluctuations on the roof, in addition to the fluctuating external pressure at the dominant opening. Wind tunnel experiments involving a flexible roof and different building porosities were carried out to validate the analytical predictions. While the effect of envelope flexibility is shown to lower the Helmholtz frequency of the building volume-opening combination, the lowering of the resonant peak in the internal and net roof pressure coefficient spectra is attributed to the increased damping in the system due to inherent background leakage and envelope flexibility. The extent of the damping effects of "skin" flexibility and background leakage in moderating the internal and net pressure response under high wind conditions is quantified using the linearized admittance functions developed. Analytical examples provided for different combinations of background leakage and envelope flexibility show that alleviation of internal and net pressure fluctuations due to these factors by as much as 40 and 15% respectively is possible compared to that for a nominally sealed rigid building of the same internal volume and opening size.

Frozen Layer Effect on Internal Cavity Pressure during Injection Molding (사출성형 공정에서 고화층이 캐비티 압력에 미치는 영향)

  • Lee H.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.474-479
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    • 2005
  • Experimental and theoretical studies of internal cavity pressure during injection molding of a spiral tube cavity were carried out. The frozen layer thickness and the evolution of internal cavity pressure were calculated using a commercial software (C-MOLD). The evolution of the internal cavity pressure was recorded during injection molding of polystyrene into a spiral tube mold. To explain the differences observed between the calculated and measured internal cavity pressure, a pressure correction factor (PCF) was introduced based on the plane stress theory. This factor was determined by analyzing the stress state in the melt and calculating the frozen layer thickness near the mold wall. The corrected and experimental pressures have been compared to validate the applicability of the pressure correction factor.

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Characteristics of wind loading on internal surface and its effect on wind-induced responses of a super-large natural-draught cooling tower

  • Zou, Yun-feng;Fu, Zheng-yi;He, Xu-hui;Jing, Hai-quan;Li, Ling-yao;Niu, Hua-wei;Chen, Zheng-qing
    • Wind and Structures
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    • v.29 no.4
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    • pp.235-246
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    • 2019
  • Wind loading is one of important loadings that should be considered in the design of large hyperbolic natural-draught cooling towers. Both external and internal surfaces of cooling tower are under the action of wind loading for cooling circulating water. In the previous studies, the wind loads on the external surface attracted concernedly attention, while the study on the internal surface was relatively ware. In the present study, the wind pressure on the internal surface of a 220 m high cooling tower is measured through wind tunnel testing, and the effect of ventilation rate of the packing layer on internal pressure is a major concern. The characteristics of internal wind pressure distribution and its effect on wind-induced responses calculated by finite element method are investigated. The results indicate that the wind loading on internal surface of the cooling tower behaves remarkable three-dimensional effect, and the pressure coefficient varies along both of height and circumferential directions. The non-uniformity is particularly strong during the construction stage. Analysis results of the effect of internal pressure on wind-induced responses show that the size and distribution characteristics of internal pressure will have some influence on wind-induced response, however, the outer pressure plays a dominant role in the wind-induced response of cooling tower, and the contribution of internal pressure to the response is small.