• Journal of the Korean Solar Energy Society
• /
• v.27 no.3
• /
• pp.127-133
• /
• 2007

Underfloor air distribution system is generally known to be more energy-saving and provide more comfort as compared with overhead air distribution system. In practice, however, some buildings to which underfloor air distribution system is applied have less effectiveness in saving energy and are getting dissatisfaction with cold draft caused by wind velocity of air distribution in terms of comfort. It is judged that such problems are due to failure to consider properties of underfloor air distribution system in applying it and identical design with the design standards for the existing overhead air distribution system. This study aims at introducing an air conditioning type of the occupied zone for underfloor all distribution system to see its effectiveness in saving energy for air conditioning of the occupied zone through a comparative simulation with the existing air conditioning type.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2000.05a
• /
• pp.146-152
• /
• 2000

As an improvement in the standard of living and economic growth the demand for air conditioning equipment is increasing rapidly. Nowadays air conditioning equipments are being used for industry large building house and car. Thess equipments was concentrated on improving heat efficiency of economic aspects while they design heat exchanger for cooling and heating,. These air conditioning equipments using heat exchanger cause a discomfort to user due to generating mist at the beginning of operating. Therefore the user demand air of high class and quality. In this experimental study to acquire elementary data for development of heat exchanger which be able to supply air of high quality that is to say possess a restraint effect of mist generation. We estimate an effect on cooling plate kind supply air velocity supply air temperature cooled plate temperature and supply air relative humidity which have an influence on outlet air condition of heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.4
• /
• pp.440-447
• /
• 1999

The frosting characteristics on the vertical parallel plates with three cooling plates were experimentally investigated. The experimental parameters were the cooling plate temperature, the air humidity, the air temperature, the air Reynolds number, and the location. The frosting conditions were limited to air temperatures from 10 to $15^{\circ}C$ , air Reynolds numbers from 1600 to 2270, air humidity ratios from 0.00275 to 0.0037kgw/kga and cooling plate temperatures from -10 to $-20^{\circ}C$. Frost growth and density toward the front of the plate were more thick and dense than toward the rear. Frost growth increased with decreasing plate temperature and increasing humidity. In the conditions of the laminar flow, dew point below $0^{\circ}C$and non-cyclic frosting period, frost thickness increased with increasing air temperature. The reason of increasing frost thickness with increasing air temperature was sublimation-ablimation process. The average growth thickness along the locations showed little dependence on the Reynolds numbers.

• Transactions of the KSME C: Technology and Education
• /
• v.2 no.2
• /
• pp.105-111
• /
• 2014

Generally the lower part of the Earth's atmosphere, which is 20km above the ground, is called "air." The composition of this area is almost consistent consisting of nitrogen, oxygen, and other gases. Air density refers to the mass per unit volume of earth atmosphere. Though air is made of the mixed gases in a constant composition, the water vapor is one of the very changeable components. The density of moist air is lower than the dry one at the same temperature and pressure. As the density varies according to the pressure and temperature, this paper attempts to explore the main factors in the air quantity calculation by examining first the density calculation process according to the air property, and second the relation between the actual and standard air flow.

• Journal of Soil and Groundwater Environment
• /
• v.15 no.1
• /
• pp.1-8
• /
• 2010

Cometabolic air sparging (CAS) is a new and innovative technology that uses air sparging principles but attempts to optimize in situ contaminant degradation by adding a growth substrate to saturated zone. CAS relies on the degradation of the primary growth substrate and cometabolic substrate transformation in the saturated zone and in the vadose zone for volatilized contaminants. In this study, we have investigated to determine MTBE degradation pattern and microbial activity variation if using propane as a primary substrate at the condition of considering air injection rate and air injection pattern. Laboratory-scale two-dimentional aquifer physical model studies were used and the experimental results were represented that the optimal conditions were as air injection rate of 1,000 mL/min and pulsed air injection pattern (15 min on/off). Over 1,000 mL/min air injection rate and continuous air injection pattern was no affected to increase DO concentration. On the other hand, Injection of propane and propane-utilizing bacteria degraded MTBE partially. And also, injection of propane- and MTBE-utilizing bacteria effectively degraded MTBE and TBA production was observed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.9
• /
• pp.581-589
• /
• 2008

The pulverized coal combustion behavior in the utility boiler is very complex since so many physical and chemical processes happen in it, simultaneously. The mixing of pulverized coal with combustion air plays an important role in achieving the efficient combustion and stable boiler operation. The distribution of combustion air supplied to the furnace through the windbox damper system has not been clearly known since the individual measurements of air flow for each air nozzle were not possible, yet. The present study describes the CFD modelling of windbox damper system and aims to obtain the air flow rates and pressure loss coefficients across the present five damper systems, respectively. The one dimensional flow network model has been also established to get air flow distributions across the windbox damper, and applied to the actual plant operation condition. Compared with the designed air flow distribution, the modelled one gives a reasonable agreement. For the actual plant operation, the predicted air flow distribution at each air nozzle is differed with the designed data and strongly affected by the individual opening angle.

• Asian Journal of Atmospheric Environment
• /
• v.1 no.1
• /
• pp.1-8
• /
• 2007

Vehicle exhaust is a dominant source of air pollutants in urban areas. Since people are easily exposed to vehicle exhaust particles while driving a car and/or traveling via public transportation, air pollution near traffic has been extensively studied in developed countries. In this paper, investigations on vehicle-related fine particulate air pollution at roadsides and on roads in Seoul, Korea were reviewed to understand air pollution near traffic. Comparison of $PM_{10}$ concentrations in Seoul showed that roadside air is more contaminated than urban air, implying that exposure levels near vehicular emissions are more critical to sensitive persons. Concentrations of ultrafine particles and BC (black carbon) at roadsides of Seoul fluctuate highly for short durations, responding to traffic situations. Diurnal variations of ultrafine particles and BC concentrations at roadsides seem to be affected by traffic volume, mixing layer height, and wind speed. Concentrations of ultrafine particles and BC decrease as distance from the road increases due to dilution during transport. On-road air pollution seems to be more severe than roadside air pollution in Seoul. Since nearby traffic air pollution has not been well understood in Seoul, further studies including various vehicular air pollutants and representative locations are needed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.566-569
• /
• 2006

The purpose of this study is to develop digital air meter used pressure sensor for measurement of air content in freshly mixed concrete by pressure method. The digital air meter can enhanced measurement accuracy and uniformity of air content in freshly concretes, according to use of pressure sensor and measuring process automation. Finally, the digital air meter in this study is improved reproducibility and reliability of measurement compared with analog air meter.

• The KSFM Journal of Fluid Machinery
• /
• v.12 no.5
• /
• pp.25-32
• /
• 2009

A study is conducted to improve the suction performance on suction devices which are used to remove polluted air generated by welding or machining process in a spacious working place of industry. Air-curtain is applied around the inlet of suction duct to interrupt the inflow of fresh air from the downstream region where is located opposite to the polluted air source. Two different air-curtain devices, such as a $45^{\circ}$ backward and a fully backward, are adopted. Suction region is experimentally investigated by measuring the suction velocities using a hot-wire anemometer. Contours of the suction velocity are compared with the computed results. The suction condition is selected to 110,000 Reynolds number which is widely used on typical suction devices, and a width of blowing passage for creating the air-curtain is chosen to 9.38% of the suction duct diameter. The experimental results show that the suction performance obtained with the $45^{\circ}$ backward air-curtain was better than that obtained with the fully backward air-curtain. On the suction duct using the $45^{\circ}$ backward air-curtain, the suction region estimated on basis of the 0.4m/sec is improved by 66% at the same input power.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.28 no.1
• /
• pp.22-33
• /
• 2020

Due to recent increased air traffic,, air traffic controllers in charge of en-route and approach control have faced huge increase in both workload and its intensity. The purpose of this paper is to analyze how much safety culture of air traffic controllers has effect on their complexity mitigation strategies during their duties. It could be expected complexity mitigation improve air traffic flow resulting in enhancing safety eventually. According to empirical analysis against air traffic controllers in civil aviation and air force in South Korea, it was proven safety culture had a statistically positive effect on complex mitigation strategies through safety behavior. In safety culture among air traffic controllers, intrinsic culture had a positive effect on extrinsic value of safety culture. Intrinsic value of safety culture led to air traffic controllers' safety behavior which created work complexity mitigation strategies. Among work complexity mitigation strategies, communication and cooperation was proven to be the most important factor effected by safety culture and behavior. It was implied that enhancing the intrinsic values of safety culture would cause to improve extrinsic safety culture and air traffic controller's work efficiency.