• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.982-992
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• 2001

In this paper, the performance of ventilation equipments in enclosed parking garages were investigated for several air distribution systems by numerical method. Air change effectiveness of the non-mixing system was 0.42. It meant that more supply air as much as the design supply air was needed to maintain good indoor air quality. In the high speed nozzle ventilating system which is most expensive one, air change effectiveness was 0.54. Therefore this system satisfied to ventilation design. In the jet fan ventilating systems, air change effectiveness for jet fan ventilating system-A with 18 jet fans and jet fan ventilating system-B with 6 jet fans in circulation mixing arrangement were 0.565 and 0.42 respectively. Jet fan ventilating system-C with 6 jet fans in transport mixing arrangement was 0.535. Jet fan ventilating system-A and jet fan ventilating system-C met the ventilation design. But velocity in jet fan ventilating system-A was over 2.0m/s which is inappropriate in human comfort. Therefore this system is not proper to ventilation. Jet fan ventilating system-C was the optimum one for enclosed parking garages among 5 systems examined in this paper.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.798-805
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• 2010

There are no domestic researches of plate fin heat exchanger in the field of cryogenic such as LNG FPSO liquefaction plant. In this study, condensing heat transfer characteristics of nitrogen according to three kinds of fin type in the plate fin heat exchanger were analyzed through simulation and experiment to secure independent technologies. In the simulation, nitrogen was condensed at 69bar and $-140^{\circ}C$ in serrated and wavy fin of plate-fin heat exchanger. The serrated fin shows the highest value of local heat transfer coefficient, followed by wavy and plain fin. The experimental results were shown errors less than 12% comparing with the simulation results.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.60-67
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• 2014

Exhaust system used in toilet and cooking place of high riser public house is roof fan of two basic types : natural roof ventilator and natural/forced roof ventilator. Natural/forced roof ventilator has a motor in the rotary shaft. There are many high riser public house in Korea. These buildings were not viewed as being major contributors to exhaust pollutants producted in indoor. It was because many engineers thought that exhaust in high riser building depend on stack effect. This study investigates on stack pressure determined by exterior pressure and the difference pressure control in exhaust stack used in high riser public house. This paper focuses mainly on the effect of the time interval for power supply of motor installed in roof fan with function of natural wind velocity and of exhaust air volume of toilet. It is observed there are higher exhaust efficiency than the existing natural roof ventilator.

• Clean Technology
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• v.20 no.2
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• pp.171-178
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• 2014

In this study we have examined the health risk factors and analyzing data of laborers working at the welding operation at large-sized casting process. In order to improve the working environment of workplace, an effective ventilation method was proposed after performing CFD (computational fluid dynamics) modeling and measurement of pollutants. As a result of examining the health risk factors of workers, oxidized steel dust is the main pollution source in the company A, welding fume in the companies B and C, and welding fume and oxidized steel dust in the company D. The fume concentration in the workers' breathing zone was $0.05{\sim}4.37mg/m^3$, and the fume concentration in the indoor air at the welding process was $0.13{\sim}7.54mg/m^3$. From a result of CFD, a local exhaust with an exhaust duct adjacent to welding point was found to be most effective in case of the exhaust process. In case of air supply, we found that a desired location of air supply fan would be at the end of the opening. If a standardizing the ventilation system for tunnel-type semi-enclosed space at a large-sized casting process is introduced in welding work places in the future, it would be more effective to protect the health of welding workers working at the casting industry and shipbuilding industry and improve the work environment.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2390-2395
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• 2007

The present research was experimentally performed to analyze the effect of delta-wing vortex generators(DWVG) on the heat transfer of fin surface of the plate fin-oval tube. The local heat transfer coefficient of the fin surface for four kinds of DWVG's arrangement was measured by the naphthalene sublimation technique for Reynolds numbers ranging from 2000 to 3200. The results showed that the heat transfer of the plate fin-oval tube can be significantly enhanced by DWVG for relatively low Reynolds numbers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.1
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• pp.79-92
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• 1998

A numerical study has been performed to obtain the air-side flow and heat transfer characteristics for a two-row lanced finned tube heat exchanger with 7 mm tube outer diameter. The increases of dimensionless local heat flux at the leading edge of slit and bottom surface of the fin were noticed. The temperature of air at downstream of the 2nd row of the lanced fin becomes more uniform than that of the plain fin because the mixing of energy increases by the slit and the side-slit. As the inlet velocity increases, the contribution of the 1st row to heat transfer decreases and that of 2nd row increases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.658-665
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• 1998

This paper investigates local exhaust effectiveness in a room with a supply and an exhaust slots on the ceiling. The mean age of air is an indicator of supply effectiveness, while the mean residual life time can be used as an indicator of exhaust effectiveness. The distribution of local mean residual life time in a space is calculated by four different numerical procedures. The reverse-flow calculation method has been proved to show quite accurate results while it can save considerable amount of computation time and efforts, compared to the method by its original definition. It is concluded that the diffusion term in the equation of mean residual life time can be neglected. The spatial and temporal diffusion characteristics of the contaminant are also discussed.