• 한국지열·수열에너지학회논문집
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• 제13권1호
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• pp.1-6
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• 2017

In this paper, the flow characteristics of water in the water supply pipes of a WBC array were evaluated. We simulated the flow velocities and pressures for a standard pipe, an expansion pipe with a concentric reducer, and an expansion pipe with an eccentric reducer using computational fluid dynamics. In the case of the standard pipe, when the inlet flow velocities were 0.5 m/s and 2.0 m/s, the maximum flow velocities at the center of the WBC array were 0.54 m/s and 2.74 m/s, respectively, which were the greatest values among those of all the pipe models considered. In the case of the expansion pipe, the maximum flow velocities at the center of the WBC array were almost the same under the same conditions regardless of the type of reducer. The pressure losses in the pipe due to the concentric and eccentric reducers were found to be (165.09 ${\times}$ inlet $velocity^{1.6677}$) and (210.98 ${\times}$ inlet $velocity^{1.6478}$), respectively. The coefficient of determination at this time was greater than 0.99 and was the same for both the models. As a simulation result, it was found that in order to reduce the pressure loss when pipe with WBC array is connected with a conventional pipe, diameter of the pipe with WBC array at that section should be enlarged by one step, and then connected to the conventional pipe with a concentric reducer.

• 에너지공학
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• 제25권1호
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• pp.86-91
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• 2016

본 논문에서는 건축 관련 기술자들이 쉽게 사용할 수 있는 도파관 배열의 길이를 계산하는 가이드라인을 제시하였으며, 대상은 원형, 사각형 및 육각형 도파관을 단위 유닛으로 하는 배열이다. 본 가이드라인은 원형 도파관의 지름, 사각형 도파관의 가장 긴 한 변의 길이 및 육각형 도파관의 장축의 길이를 기준으로 간단하게 각 도파관 배열의 길이를 결정할 수 있는 그래프와 Table을 제시하는 것을 목표로 하였다. 연구결과, 지름 및 가장 긴 한변의 길이, 장축의 길이를 30 mm로 기준으로 하면, 차폐성능이 80 dB의 효과를 목표로 하면 육각형 도파관 배열의 길이가 사각형 도파관보다 5 mm 정도 짧아지게 된다. 또한 100 dB 차폐 성능을 목표로 할 경우 30 mm정도 짧은 것으로 나타났다. 원형 도파관을 비교하면 80 dB와 100 dB 모두 육각형 형태의 도파관을 사용하는 것이 도파관 배열의 길이를 13 mm 정도 단축시킬 수 있다. 따라서 동일한 차폐성능을 가지는 경우 압력손실을 고려하면 육각형 도파관을 사용하는 것이 가장 효율적 일것으로 판단된다.

• 한국지열·수열에너지학회논문집
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• 제12권1호
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• pp.1-6
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• 2016

Characteristics of exhaust from chimney of electricity generator are analyzed based on CFD when Waveguide-Below-Cutoff (WBC) array is installed in order to achieve the certain level of electromagnetic pulse (EMP) shielding. The main purpose is prediction of average and maximum velocity of exhaust. The results reveal that: 1) When the specification of waveguide is given as 80-diameter, 400-length, and the gap of 20 mm, the shielding effectiveness (SE) is 140dB. The average and maximum velocity of exhaust in the chimney with WBC Array can be represented as exponential functions. 2) As the number of WBC increases, the velocity in the chimney dwindles. 3) Under the situation that WBC with 80 mm diameter is located at intervals of 20 mm, the average velocity can be approximated by $25.5344{\times}e^{(-0.0098{\times}N_{WBC})}$ with input velocity of 15 m/s. In addition, the determination coefficient is 0.915, which is sufficiently high.

• 에너지공학
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• 제24권4호
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• pp.159-165
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• 2015

본 논문에서는 EMP 차폐를 위한 WBC 배열이 설치된 대형 비상발전기 연도의 최적형상을 결정하는 것을 목표로 연구를 진행하였다. 시뮬레이션은 WBC 배열의 외부관경이 800, 850, 900, 1050mm 및 1250mm를 대상으로 하였으며 기본연도와의 접속길이를 150, 300, 450 mm, 연도의 유속은 15, 20, 25m/s로 하였다. EMP 차폐를 위한 WBC 배열을 연도에 설치하는 경우 WBC 배열의 외부관경, Main 연도와의 접속길이가 배기가스 흐름에 큰 영향을 미치는 것으로 나타났다. WBC 배열의 외부관경이 1050, 1250mm이고 접속길이가 300, 450mm이면 도파관 배열에서 배기가스의 평균속도와 최고속도를 만족시키는 것으로 나타났다.

• 한국지열·수열에너지학회논문집
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• 제12권3호
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• pp.1-8
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• 2016

In this study, we evaluated the flow characteristics of various types of waveguide-below-cutoff (WBC) arrays and their shielding effectiveness (SE) of electromagnetic pulses (EMP) based on computational fluid dynamics (CFD). Three types of waveguides were selected for analysis: (1) grid type, (2) honeycomb type, and (3) multi-layer types (2-ply, 4-ply, 6-ply, and 8-ply). To analyze the air flow characteristics, the flow velocities in the longitudinal center of the WBC and the differential pressures between the WBC array inlet and outlet were evaluated. Consequently, we derive the following conclusions: (1) despite an increase in the inlet velocity, the pressure drop of the 6-ply multi-layer type did not significantly increase as compared to that of other types of waveguides (waveguide thickness of 0.1 mm, SE of 100 dB); (2) the grid and honeycomb type had the fastest flow rate of 17.5 m/s, which is approximately 2.5 m/s faster than that at the inlet (waveguide thickness of 1 mm, module size of 30 mm); and (3) the average pressure drop of the grid type waveguide is the lowest in the overall model, whereas that of the 8-ply is the highest (waveguide thickness of 1 mm, module size of 30 mm, and SE of 80, 100 dB).

• 설비공학논문집
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• 제29권7호
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• pp.366-372
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• 2017

The objective of this study was to characterize Waveguide-Blow-Cutoff (WBC) array for Electromagnetic Pulse (EMP) shield in air duct or water pipe, the typical pathway of pulse in indoor space with critical electronic device. A numerical investigation with three different WBC designs (circular, rectangular, and hexagonal or honeycomb) was conducted to satisfy recommended shielding effectiveness (SE) levels from 80 dB to 140 dB. Pressure drop between upstream and downstream of EMP shields based on WBC arrays was also investigated to understand air flow feature in air duct of HVAC system. Results showed that honeycomb geometry outperformed other shapes in terms of reducing the depth of EMP shield, thus providing better air flow in duct path with lower local loss coefficient in HVAC system under SE requirements.