• Tunnel and Underground Space
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• v.13 no.4
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• pp.287-293
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• 2003

A long vertical duct is an essential installation for extracting smoke to the ground level when a fire occurs in an underground space. Due to the limitations of its basic assumptions, the existing two-layer zone model is unsuitable to model smoke dispersion through a long vertical duct. Therefore, an assessment was made to investigate the applicability of the field model, which is based on the computational fluid dynamics (CFD). A similar configuration to the published experimental work was modeled to test the validity. It is clear that under a consistent decision criterion based on the mass fraction, the field model (CFD) is able to predict that the diffusion front progresses up the shaft with exactly the same rate as that in the empirical correlation equation. This result is for better than the mathematically obtained equations in previously published research. Therefore, it can be said that the field model is an excellent option to predict the smoke dispersion through the long vertical shaft.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.139-146
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• 2011

The ventilation performance of a vertical exhaust duct system in the high riser public house has been evaluated by a commercial software, Fluid Flow, which solves pressure losses through the duct system including bathroom fans and a hybrid roof fan. During the numerical simulations, outdoor wind condition and stack effects in summer and winter were considered as well as the operating conditions of a basement damper and the roof fan. The results show that the bathroom ventilation in summer is the most unsatisfactory. The opening of the basement damper has a problem that the polluted air in the lower floors is exhausted to the underground parking lot, not to the rooftop. If the basement damper is closed, the exhaust flow rate in the lower floors is not sufficient due to the strong flow resistance in the long vertical duct even though the roof fan is under operating.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.1-6
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• 2001

An experimental study was carried out to investigate the emission characteristics of LP gas burner for the Practical combustion conditions including fm voltage, inlet area, gas Pressure, emission resistance, duct length and height. The result shows that CO is almost remains constant for the emission fan voltage, but significantly increases with the reduction rate of air inlet, up to 3000ppm at 50% of reduction rate. Also, the variation of gas pressure has no effect to CO of gas boiler due to its governor which controls gas pressure secondly, but it gives an rapid increase of CO for the gas range. The emission resistance test shows that CO is suddenly increased with the reduction rate of emission duct above 70% and main burner is stopped at 90%. The reverse wind test shows that CO is suddenly increased with the air velocity above 7m/s and main burner is stopped at 9m/s. The more horizontal length of emission duct is long and the vertical height is low, CO is infinitesimally increased.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.153-166
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• 2015

Long subsea tunnel to be built below the seabed, as compared to the general railway tunnel, is subject to many restrictions in terms of spatial limitation when vertical or inclined shafts are built for the purpose of ventilation and fire safety. So, the construction of some artificial island is required to provide ventilation. But, because of construction difficulty and cost increase, it is necessary to minimize the artificial island construction. The longer ventilation distance is, the more fresh air requirement is needed. When supply airflow becomes excessive, duct size is restricted by the limitations of structure clearance and fan pressure and power increase exponentially. Therefore, in order to build a long subsea tunnel, it is necessary to overcome these practical problems and to develop technical solution that can keep the comfortable condition of tunnel environment during construction. In this study, as on ventilation method development suitable for long subsea tunnel, through comparison of temporary ventilation capacity calculation methods during construction phase, domestic and abroad, the application of Swiss SIA 196 code is found suitable for long subsea tunnel. And, through experiment on leakage of the duct connector, we confirmed that the leakage ratio per 100 m of domestic duct connection type is between 1.5~3.0%. Based on S-class duct of SIA 196 code, ventilation distance is 10.2 km, So, ventilation distance can be longer if duct connection method is improved. So, we confirmed that the improvement of leakage ratio is key issue in the construction-phase ventilation of long subsea tunnel.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.119-125
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• 1998

In long vertical duct, the aspect of second flame in laminar flame propagating through lycopodium-air mixtures and the behavior of dust particles in neighborhood in front of flame have been examined experimentally. In order to trace the development of second flame to its origin, the velocity and vorticity distribution of dust particles in front of flame were measured by using with the real-time PIV system. The velocity of particles was approximately zero at the central part of flame front and the ahead of the flame leading edge, but maximum near the duct wall. The flame velocity of second flame and the movement of leading flame edge depend mainly on behavior of dust particles by the flow distribution of temperature and pressure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.145-160
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• 2018

Long subsea tunnel is subject to many restrictions in terms of spatial limitation when vertical or inclined shafts are built for tunnel ventilation. So, the construction of some artificial island is required to provide ventilation. But, because of construction difficulty and cost increase, it is necessary to minimize the artificial island construction. As a result, ventilation distance become longer and supply airflow becomes excessive due to air leakage, So, duct mounting for temporary ventilation is impossible or fan pressure and power increase exponentially. Therefore, in order to build a long subsea tunnel, it is necessary to overcome these practical problems and to develop technical solution that can keep the comfortable condition of tunnel environment during construction. In previous study, we have found that air leakage is the key factor in solving these problems and experimental results show that the new connection method has a leakage rate of about $1.46mm^2/m^2$ (Jo et al., 2017). In this study, we present the experimental results of the measurement of the leakage rate of the prototype with the new connection method, and analyze experimentally the improvement of the leakage rate when applying the flexible cover inside the duct to improve the leakage performance of the existing connection method.

• Journal of Animal Environmental Science
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• v.16 no.1
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• pp.41-50
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• 2010

The goal of this study was to develop a suitable ventilation system for high-rise hog building (HRHB) for growing-fattening with combined slatted floor pen in second story and in situ manure management system in Korea. The HRHB was constructed as 29m long, 9m wide and 7.6m high for outer dimension with an indoor height of 3.1m and 2.4 for lower and upper floor, respectively. Ventilation systems for each treatment were installed in separated rooms of HRHB. The ventilation types installed in each room were following 3 types: ventilation type 1 (V1), where air was pulled through a circular duct inlet and exhausted by fans; ventilation type 2 (V2), where air was pulled through eave inlet (side ceiling inlet) and exhausted by fans; and ventilation type 3 (V3), where air was pulled through baffled ceiling inlet and exhausted by fans. For each ventilation system, investigated air velocity under minimum, medium and maximum ventilation ratio and air flow pattern inside. The results were as follows; For air flow pattern from top to bottom, V1 showed a homogeneous vertical type, V2 showed a bilateral symmetry type and V3 showed an vertical umbrella type. Under minimum ventilation ratio, air velocity in upper floor (80cm above the slated floor) was similar for V1, V2, and V3. Under maximum ventilation ratio, air velocity in upper floor was undeviating for V1 (0.10~0.26m/s) and varied for V2 (0.12~0.63m/s) while those for V3 was relatively slow and less varied (0.07~0.15m/s). In conclusion, Duct inlet type (V1) can be applied to the development of a new HRHB with additional evaluations such as field test hog feeding.