• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.736-743
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• 2005

In this study, three different types of mechanical ventilation systems are compared based on their ventilation characteristics: tracer gas concentration decay characteristics, and ventilation effectiveness by calculating actual ventilation air flow rate. The experiments are performed by using a step-down method for measuring tracer gas. $CO_{2}$ gas, concentration in the model chamber. Application of a mixing factor, k, was used and measured values ranged from 0.68 to 0.77. The Type 2 ventilation system was found to have the highest ventilation effectiveness rather than the Types 1 and 3.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.40-45
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• 2003

To evaluate the smoke control systems, the large eddy simulation turbulence model based Fire Dynamics Simulate was applied to a 2m $\times$ 2m $\times$ 2.4m room with an opening. The smoke removal rate was investigated for three different smoke control systems: ventilation, extraction and pressurization. When the opening was closed, the smoke removal rates of the smoke control systems were almost the same as expected. The pressurization system showed a lower smoke removal rate compared with the other two smoke control systems for the room with the opening, and hence the pressurization system might not be efficient for a place with large openings. It was shown that the lower extraction flowrate is, the longer time the ventilation system requires to remove smoke. From these results, the ventilation system is recommended for subway stations where several large openings exist.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.8
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• pp.1310-1315
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• 1999

Air quality in confinement pig houses is important to production and health. Mechanical ventilation and confinement is known to be the most practical tool for maintaining adequate air quality in pig houses through extensive researches since Millier (1950) invented the 'slotted inlet' ventilation system. A variety of mechanical ventilation systems have been applied to confined nursery pig houses in Korea without scientific verification of their ventilation effectiveness. Ventilation systems with three feasible combinations (NA, NB, and NC) of inlets and outlets in a confined nursery pig house were tested to evaluate their ventilation efficiency, of which the one with the performance was supposed to be taken as a standard ventilation system for nursery pig houses in Korea. Field data of air velocity and temperature fields, and ammonia concentration with three ventilation systems were taken and compared to determine the best system. The air velocity and temperature fields predicted by the PHOENICS computer program were also validated against the available experimental data to investigate the feasibility of computer simulation of air and temperature distribution with an acceptable accuracy in a confined house. NC system with duct-induced in-coming air, performed best among the three different ventilation systems, which created higher velocity field and evener distribution ($2.5m/s{\pm}0.3m/s$) over the space with a Reynolds number of $10^4$. The experimental data obtained also fitted well with the simulated values using the modified PHOENICS, which suggested a viable tool for the prediction of air and temperature field with given calculation geometries.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.5
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• pp.187-194
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• 2020

This study presents the energy-saving sequential control algorithm to handle indoor CO₂ and PM2.5 for the improvement of the air quality of school classrooms. To solve indoor air quality (IAQ) problems, air cleaning and ventilation systems are mainly used for school classrooms. Although air cleaning is able to collect PM2.5, it is difficult to remove harmful gas substances. The ventilation system is suitable to tackle CO and CO₂, the volume ventilation, however, is relatively small. In this paper, to remove CO₂ and PM2.5, the pollutant balance equation for improving indoor air quality is reviewed. The sequential control algorithm of the ventilation and air cleaning system with four levels of criteria is introduced for the effective removal of pollutants. The proposed sequential control algorithm confirms that indoor CO₂ and PM2.5 can be properly controlled below the standard value. In addition, the sequential operation of air cleaning and ventilation systems has shown significant improvement in IAQ compared to the independent ventilation system operation. Particularly, such systems are efficient when outdoor PM2.5 is high.

• Wind and Structures
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• v.19 no.2
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• pp.185-197
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• 2014

Ventilation and fire safety design in road tunnels are one of the most complex issues that need to be carefully considered and analysed in the designing stage of any potential upgrade of ventilation and other fire safety systems in tunnels. Placement road tunnels space has an important influence on fire safety, especially when considering the effect of adverse wind conditions that significantly influence ventilation characteristics. The appropriate analysis of fire and smoke control is almost impossible without the use of modern simulation tools (e.g., CFD) due to a large number of influential parameters and consequently extensive data. The impact of the strong wind is briefly presented in this paper in the case of a longitudinally ventilated road tunnel Kastelec, which is exposed to various severe wind conditions that significantly influence its fire safety. The possibility of using CFD simulations in the analysis of the tunnel placement in space terms negative effect of wind influence on the tunnel ventilation is clearly indicated.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.3 no.2
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• pp.152-165
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• 1993

This study was performed at eleven small-sized plating factories located in Seoul, Incheon, Ansan, and Taejeon from July 21 to October 6, 1992. The major objectives of this study were to evaluate worker exposure to hexavalent chromium and local exhaust ventilation (L.E.V.) systems at the chromium plating operations. The most suitable L.E.V. systems for chromium plating tanks were designed as examples for recommendation to the industry. The results are summarized as follows. The range of chromium plating operations investigated included decorative, hard, and black chromium plating on several kinds of parts. Most of plating tanks were not equipped with proper control methods against emission of hexavalent chromium mists and workers were not wearing appropriate personal protectives. The ariborne hexavalent chromium concentrations showed an approximate lognormal distribution. The geometric means of both personal and area samples were within the Korean and ACGIH standards, $50{\mu}g/m^3$. However, in comparison with the NIOSH criterion, $1{\mu}g/m^3$, the geometric means of personal samples at two factories and the geometric means of area samples at two factories exceeded it. The geometric means of personal and area samples of high exposure groups (above the NIOSH criterion) were 7 and 27 times higher than those of low exposure groups (below the NIOSH criterion), respectively. The L.E.V. systems of high exposure groups were improperly designed, and the factory with the highest exposure level had no L.E.V. systems at all on chemical etching process. Whereas at factories of low exposure groups, mist control methods such as mist suppressants, tank cover, and/or auxillary L.E.V. systems were added to L.E.V systems. The evaluation of L.E.V. systems showed that there was no chromium plating operation satisfying the ACGIH criteria for capture velocity, slot velocity, and exhaust rate simultaneously. To increase performance of L.E.V. systems, it must be designed to minimize the impact of boundary layer separation. Push-pull ventilation hood and downward plenum ventilation hood were suggested for the Korean industry.

• Journal of Environmental Science International
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• v.20 no.5
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• pp.581-587
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• 2011

Industrial natural ventilation systems consist of gravity ventilator, the high/low windows and doors. Especially, the high windows play an important role in the industrial natural ventilation systems. Generally speaking, industrial high windows are divided into 3 types; louver type, $45^{\circ}$ open type and $90^{\circ}$ open type. This study was numerically and experimentally conducted. Three types of windows were tested to know the ventilation characteristics and estimate the ventilation efficiencies. Numerically, computational fluid dynamics software (AIR PAK Ver. 2.0) was used to observe the flow characteristics inside the industrial building and the concentration contours generated by the tracer gas method. Experimentally, the flow visualization technique and the tracer gas method were applied with the model building to characterize the flow pattern inside the model building and to estimate the ventilation efficiencies with the different windows. It was found that $90^{\circ}$ open type window was most effective for the discharge of pollutants from the industrial building. On the other hand, the louver type window was found to be less effective than any other windows.

• Journal of the Korean Institute of Educational Facilities
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• v.11 no.2
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• pp.17-23
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• 2004

The purpose of this study concerns the improvement of air quality in school classrooms. Polluted indoor air is improved by efficient ventilation systems. So it is important to measure the amount of ventilation needed in classrooms. First, the amount of natural ventilation were measured through a tracer gas method. And we have established a heat recovery ventilation system from 4 cases of airflow in classrooms, and we have measured the change of $CO_2$ density. According to air quality measurements in the classrooms, the density of $CO_2$ is well above environmental standards which are acceptable. When the amount of ventilated airflow increases, indoor air quality is improved. It is surveyed that the most suitable amount of external inducted air is 770 CMH to satisfy $CO_2$ less than 1,000 ppm in classrooms. For improvement of air quality in classrooms, we must consider a suitable ventilation plan and installation of ventilation systems when constructing school buildings.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.1 s.139
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• pp.10-17
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• 2005

Due to emission of vehicles during loading/unloading, ventilation system in Roll-on/Roll-off ship is inevitable; however it is very difficult to predict the ventilation performance before it is finally built in. Although the requirements for the ventilation system include air change rate and maximum allowable concentration of CO in the cargo holds, even prototype tests are hardly able to quantify the ventilation performance. In the present paper, a new method to assess the ventilation performance of Roll-on/Roll-off ship is proposed by using computational fluid dynamics. The air exchange is modeled by introducing multi-species transport of existing air In the holds and new air from the ventilation system. Conservation of multi-species as well as 3D Navier-Stokes equation are solved numerically in time dependent manner. Several cases of different configuration are considered. The results include predicted mass fraction of new air in the holds. It is also presented that CO concentration can be estimated based on the predicted air change performance. Due to the lack of experimental data, the computed results are not verified; however the proposed method can be applied as au assessment tool.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.87-92
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• 2001

In automobile highway tunnels, in order to maintain a suitable environment for drivers and traffic, visibility in the tunnel must be maintained, and the concentrations of poisonous substances including carbon monoxide must be kept at or below allowable levels. For this reason, in long tunnels and tunnels with heavy traffic, ventilation facilities are installed. When the ventilation facilities are run at full capacity, the environment in the tunnel is obviously adequately maintained, but this consumes a great deal of electric power. Consequently, a central problem in highway tunnel ventilation control systems is to keep the pollution concentration at or below the allowable level, and thus provide a safe environment for traffic, while consuming as little electricity as possible. This paper introduces an operation method of longitudinal flow ventilation systems with jet-fan, dust collector and vertical ducts.