• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.29 no.7
• /
• pp.366-372
• /
• 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.

• Fire Science and Engineering
• /
• v.30 no.4
• /
• pp.94-102
• /
• 2016

When establishing shielding facilities for EMP protection, WBC effect is used to protect fire pipes and honeycomb cells are inserted into the fire pipes to improve the shielding effectiveness. At this point, the smaller unit cell of honeycombs becomes, the more likely it interrupts the flow of water, which ends up clogging the fire pipes with sediment. To prevent this phenomenon, I would suggest a design method due to the pilarization loss of water molecules that contributes to increasing the size of honeycomb cells and remaining thin-walled sufficient for required shielding effectiveness.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.12 no.3
• /
• pp.1-8
• /
• 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).

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.10 no.4
• /
• pp.15-24
• /
• 2014

This study conducted a computational fluid dynamics(CFD) analysis to find an appropriate diameter or sectional area of air ducts and fluid pipes which have an electromagnetic pulse(EMP) shied to protect indoor electronic devices in special buildings like military fortifications. The result shows that the optimized outdoor air intake size can be defined with either the ratio of the maximum air velocity in the supply duct to the air intake size, or the shape ratio of indoor supply diffuser to the outdoor air intake. In the case of water channel, the fluid velocity at EMP shield with the identical size of the pipe, decreases by 25% in average due to the resistance of the shield. The enlargement of diameter at the shield, 2 step, improves the fluid flow. It illustrated that the diameter of downstream pipe size is 1step larger than the upstream for providing the design flow rate. The shield increases friction and resistance, in the case of oil pipe, so the average flow velocity at the middle of the shield increase by 50% in average. In consideration of the fluid viscosity, the oil pipe should be enlarged 4 or 5 step from the typical design configuration. Therefore, the fluid channel size for air, water, and oil, should be reconsidered by the engineering approach when EMP shield is placed in the middle of channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.4
• /
• pp.426-433
• /
• 2014

The high-altitude electromagnetic pulse(HEMP) generated by a high-altitude nuclear explosion. This paper presents the comparison of electric field penetration in Bell laboratories and IEC 61000-2-9 standard when HEMP source penetrates through Naval Warship conducted coupling path and radiated coupling path. Also we analyze the effects of two kinds of coupling and propose Protective measures. Simulation results confirm IEC 61000-2-9 standard is more strict than the Bell Laboratories standard except for a lower frequency band, so we proposed IEC 61000-2-9 standard as a Naval HEMP standard. Finally, we offer the protective measures such as the shielding coating, Honeycomb ventilation, TVS in order to meet the military criteria.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.6
• /
• pp.452-458
• /
• 2017

Multi-layered Waveguide-Below-Cutoff Array(WBCA) used in air duct and water pipe has advantages in manufacturing process as well as flow characteristics. In addition, it is possible to increase the Shielding Effectiveness(SE) by increasing the number of layers. However, since the SE of the multi-layered WBCA can not be predicted by the conventional SE equation, we propose the modified SE equation. The modified SE equation is obtained for both air and arbitrary fluid flowing in a multi-layered WBCA by increasing the number of layers from 2 to 64. In order to confirm the validity, the results of the proposed SE equations are compared with the EM simulation results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.8
• /
• pp.735-741
• /
• 2016

Increasing the total length of waveguide-below-cutoff array(WBCA) as it is used to the duct in order to enhance shielding effectiveness, the design could cause higher cost, higher levels of difficulties in construction and the interruption a flow velocity. The multi-layered WBCA can compensate for this problem, which can be designed by crossing each waveguide layer. By conducting simulations from 2-layer to 8-layer structure, it can be observed that the shielding effectiveness increases from 52 dB to 75 dB. Comparing with the original WBCA in a shape of mono layer rectangular, our proposed waveguide becomes similar with the original value as the number of crossing layer increases. In addition, the analysis with the flow of fluid in the duct installed multi-layered WBCA are required. We demonstrate this analysis by doing the flow of fluid simulation, and concluded that the multi-layered WBCA has loss of flow of fluid less than unit rectangular WBCA.