• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.109-117
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• 2005

In this study, the 1/20 reduced-scale experiments using Froude scaling were conducted to investigate the ventilation velocity of the variation of burning rate in tunnel fires. The heptane square pool fire with heat release rate ranging from 3.71~15.6 kW were used. The burning rate of fuel was obtained by measuring mass using load cell and temperature distributions were measured by K-type theomocouples in order to investigate smoke movement. The ventilation velocity in the tested tunnel was controlled by inverter of the wind tunnel. In heptane pool fire case, the increase in ventilation velocity incresed the burning rate due to the direct supply of oxygen to the fire plume. For the same dimensionless velocity($\bar{V}$), burning rate increased as the size of pool fire decreased.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.3
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• pp.343-350
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• 2019

Objectives: This study aims to identify whether ventilation conditions and their effectiveness can be significantly improved in an experimental chamber by increasing the mixing factor (K-Factor). Methods: In a chamber with a volume of $1m^3$, air velocity was measured at six different points with four roof fans in the upper part of the chamber being operated in order. The impact of the ventilation conditions was analyzed when the flow rates were increasing and the first inlet of the chamber was either open or closed. Smoke patterns were also observed at four corner points where ventilation was limited. Kruskal Wallis and Mann-Whitney tests were performed to compare air velocities measured in the chamber. Results: The air velocities measured at only the third point increased significantly from $0.03{\pm}0.03m/s$ (door open) and $0.05{\pm}0.06m/s$ (door closed) with two fans, $0.08{\pm}0.08m/s$ with three fans, and $0.09{\pm}0.09m/s$ with four fans operating (p<0.05). However, air velocities at the four corner points did not significantly increase. Smoke patters also showed that the open inlet of the chamber had no effect on improvement of ventilation conditions and effectiveness. Conclusions: In this study, the air velocities at six points in the chamber did not significantly increase despite the increase in the mixing factor and flow rates of ventilation in the controlled environment. Therefore, the inflow of outdoor air throughout an open inlet and installation of a forced ventilation system can potentially increase the indoor air velocity and improve ventilation condition without an increase in the mixing factor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.16-22
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• 2018

This study is about flow distribution in ventilation systems used in marine louvers. The flow analysis on a louver installed on the vent of a vessel results in the following conclusions: (a) as the velocity of the fluid entering the louver increases, the pressure drop increases; (b) as the pressure drop increases, it tends to increase following a quadratic function. The velocity was confirmed to decrease at the entrance of the louver. This indicates that as the pressure increases, the velocity decreases, and the velocity of the moving fluid is increasing as it passes through the louver vanes.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.46-49
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• 2005

Vents at outer walls of a large factory building are very important for natural ventilation. But, if a full-open vent is used, rain comes through the vents. We tried to utilize the natural ventilation effectively using a louver. A 1/120 scale-down building model was placed inside an atmospheric boundary layer simulated in a wind tunnel test section. The effect of louver angle on the ventilation flow inside the factory building was investigated experimentally. Instantaneous velocity fields inside the building model were measured using a 2-frame PIV system with varying the louver angles ($\theta=20^{\circ},\;40^{\circ},\;60^{\circ}$). For the case of $\theta=60^{\circ}$, as the incoming flow into the factory building increases, the inside velocity distribution becomes uniformly.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.496-500
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• 2010

Understanding train-wind is the best method to know how to optimize subway ventilation system. The capacity and efficiency of the subway ventilation system are known by pressure and velocity while train runs. Analysis of the internal flow in subway tunnel and around subway station are studied using numerical methods. Characteristics of internal flow and influence of subway ventilation system for the subway station with platform screen door and tunnel are analyzed by unsteady state analysis. Velocity and pressure of train wind transformation are compared at around subway ventilation system and the internal flow is investigated at the subway tunnel.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.72-79
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• 2000

In recent, occupational diseases in harmful working places become a social issue. It is the well-known fact that a respiration in polluted working places exert a serious effect on health of workers. Accordingly, the cutting off contaminants air originally is the best way to improve working environments. In these cases, ventilation systems should be essentially installed to dilute or exhaust the contaminated indoor air. In this study, we investigated the characteristics of ventilation system of the noxious gas in working indoor places with natural ventilation by using COMET. The numerical simulations were carried out the natural ventilation with two phase(air, dust). For turbulent flow, Reynolds stresses were closed by the standard $\kappa$-$\varepsilon$ model. The results are as follows ; 1) In the natural exhaust in the working place, the flows of the central region have a more rapid velocity vector than the right and left one. 2) Numerical results show that the distribution of contaminants concentration have greater influence on convection than the case of diffusion by government of velocity vectors. 3) To observe the velocity variation with distance, three location of distance are considered. As results, it shows that the velocity are 0.075(m/s) at y=5(m), 10(m) and mean concentration are raised 10.6% at y=5(m), 10(m). 4) We have presented the useful data for the adequate counterplan in the harmful working places by carrying out the various investigation of the natural ventilation.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.3 no.2
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• pp.204-212
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• 1993

This study was conducted to evaluate ventilation efficiency of 4-stage slot hood by variation of slot width, flow rate, hood size and baffle size. The slot velocity, control velocity and plenum velocity were related to slot width and the distance between source of contamination and hood. The results obtained from laboratory experiment for local exhaust ventilation systems were as follows ; 1. When slot widths were constant(equally changed) and the velocity was 6-10 m/s, the slot velocity from 1st slot to 4th slot gradually decreased. As the slot width-to-slot length ratio(WLR) decreased, the slot velocity of each stage increased. But if WLR value was less than 0.04, the slot velocity decreased. 2. When slot velocity exceeded 10 m/s with constant slot widths, the slot velocity of each stage was uniform. 3. When the slot velocity was uniform within 10 m/s and the first slot width was 14-20 mm, the slot width ratio between 1st slot and each of three other slots were 1, 1.25, 1.5 and 3.0, respectively. 4. The slot and plenum velocity were uniform when exhaust flow rate changed from 14 to $19m^3/min$ and there were no hood splitter vanes. 5. When the slot velocity at each stage was uniform, the control velocity at site 30 cm away from hood No.2 increased from 0.15-0.30 to 0.25-0.45 m/s and the control distance from 20 to 30 cm(about 1.5 times).

• Journal of Biosystems Engineering
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• v.36 no.6
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• pp.444-452
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• 2011

In this study the characteristics of natural ventilation of Venlo-type greenhouse with continuous roof vents were analyzed using commercial computational fluid dynamics (CFD) code. Developed CFD simulation model was verified by comparison with experimental data. Simulation errors were 1.9-46.0% for air velocity and 1.7-11.2% for air temperature at each measurement point. CFD simulations were conducted to estimate the effect of roof vents opening direction, opening angle, outside wind velocity and wind directions on ventilation rate and climate condition in greenhouse. The results of this study showed that ventilation rate of the present greenhouse was increased linearly in proportion to the increase of roof vent opening angle and outside wind velocity over 2.0 m/s. According to the analysis on the effects of different roof vent opening direction, simultaneous opening of wind and leeward vents showed the highest ventilation rate and lowest mean temperature in greenhouse.

• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.175-181
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• 2006

Nursery pig building is imperative to provide environmental conditions favorable to maintenance of piglet health and the efficiency of growth rate. To meet the ultimate goal, it is necessary to apply proper ventilation design and construction to a confinement livestock building. This study was conducted to investigate the performance of a modified ventilation system in terms of devised slot-inlet (modification I) and exhaust fan (modification II) to improve air change rate in a confined nursery pig building, with dimension of 5.9 m(W) ${\times}$ 12.6 m(L) ${\times}$ 2.2 m(H) in an Darby Genetic Station. The experiment was carried out in August, especially when the outdoor peak temperature were above $30^{\circ}C$ and the measured indoor environmental factors were temperature, air velocity, humidity and ammonia concentration which have been known to affect the piglet health and growth. There was no difference in indoor temperature between the original and modified ventilation systems, however the air velocity and ammonia concentration in confined nursery pig building with modified ventilation system were, in most cases, better performance than original ventilation system. Therefore, it was concluded that the slot-inlet system that kept indoor environmental factors pertinent and had an economic advantage, should be considered as a ventilation system for decreasing sensible heat from piglet in confined nursery pig building during extreme summer season.

• KIEAE Journal
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• v.6 no.2
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• pp.43-50
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• 2006

A Double Facade System(DFS) is well known as an innovative solution of ecological facade in the west european countries. There are more than 200 various realized DFS in Germany. At the same time, the korean engineers have researched to find out the physical advantages of DFS in the moderate korean climate, which has a very humid summer with high temperature and a dry winter with low temperature. For example, the monthly mean temperature in Korea comes up to 28K, while that in Germany comes up to only 19K. That is, why a other solution of DFS is needed in Korea. This study has experimented the physical performance of the natural ventilation in the heating period. The preheating function of the cold air by DFS can improve no doubt the performance of the natural ventilation at the cold season as well as spring and autumn. The physical difference between single and double facade on natural ventilation has been tested at the newly constructed laboratory, which can turn $360^{\circ}$ to confirm the characteristic of a facade with the various directions. The results show the natural ventilation of the DFS has definitely much more comfortable than that of the single facade system. The air velocity of the inflow as well as the air temperature in the DFS provide a more stable condition than in the SFS. The theoretical limit(air velocity max 0.2m/s, air temperature min. $18^{\circ}C$, temperature difference between 100mm and 1700mm height max. 3K) on the indoor comfortableness doesn't go over in the DFS. On the other hand, the SFS showed an unstable condition with an excess of comfortableness limit on air velocity as well as temperature. In view of the researching results so far achieved, the research came to a conclusion, that the DFS can provide a more comfortable indoor condition by the preheating in the heating period than a SFS, and the period of natural ventilation in winter time could be definitely increased at the DFS.