• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.49-55
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• 2012

In order to derive the efficient utilization of low pressure compressed air fogging system, cooling efficiencies with control types were analyzed through cooling experiments in tomato greenhouses. The control types were set up with temperature control, humidity control, temperature and humidity control, and time control. It showed that the cooling effects were 0.7 to $3.3^{\circ}C$ on average and maximum of 4.3 to $7.0^{\circ}C$, the humidification effects were 3.5 to 13.5 % on average and maximum of 14.3 to 24.4 %. Both the cooling and humidification effect were the highest in the time control method. The cooling efficiency of the air fogging system was not high with 8.3 to 27.3 % on average. However, the cooling efficiency of 24.6 to 27.3 % which appears from the time control is similar to the cooling efficiency of high pressure fogging system experimented in Japan. The air fogging system is operated by low pressure, but its efficiency is similar to high pressure. We think because it uses compressed air. From this point of view, we suggest that the air fogging system can get the cooling efficiency of similar levels to that of high pressure fogging system and it will have an advantage from clogging problem of nozzle etc.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.423-432
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• 2018

Since the Daegu subway fire accident, people's perception of safety has increased, and all materials inside the train have been changed to incombustible materials. However, there is still a lack of development of fire extinguishing systems. Train components are mostly made of steel plates, and therefore it is very difficult to extinguish the train fire by using general fire extinguishing equipment. In this regard, this paper investigated rapid and easy methods of extinguishing the train fire by using compressed air foam systems through full-scale fire tests. To extinguish the fire of train at rescue station, window breakers were used to quickly destroy the train windows, and the compressed air foam system was inserted inside the train. As a result, the train windows were destroyed in 5 seconds, and the 11.88-MW fire was put out in 30 seconds by the compressed air foam discharged from the compressed air foam system inserted inside the train. For the future work, there is a need for further experimental studies to prevent the spread of fire and protect tunnel structures with the use of compressed air foam systems.

• Structural Engineering and Mechanics
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• v.71 no.4
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• pp.363-375
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• 2019

A renewable energy storage pile foundation system is being developed through a multi-disciplinary research project. This system intends to use reinforced concrete pile foundations configured with hollowed sections to store renewable energy generated from solar panels attached to building structures in the form of compressed air. However previous research indicates that the compressed air will generate considerable high circumferential tensile stresses in the concrete pile, which requires unrealistic high hoop reinforcement ratio to avoid leakage of the compressed air. One possible solution is to utilize fiber reinforced concrete instead of placing the hoop reinforcement to resist the tensile stress. This paper investigates nonlinear structural responses and post-cracking behavior of the fiber reinforced concrete pile subjected to high air pressure through nonlinear finite element simulations. Concrete damage plasticity models were used in the simulation. Several parameters were considered in the study including concrete grade, fiber content, and thickness of the pile section. The air pressures which the pile can resist at different crack depths along the pile section were identified. Design recommendations were provided for the energy storage pile foundation using the fiber reinforced concrete.

• Geomechanics and Engineering
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• v.13 no.1
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• pp.1-23
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• 2017

A coupled liquid-gas-solid three-phase model, linking two numerical codes (TOUGH2/EOS3 and $FLAC^{3D}$), was firstly established and validated by simulating an in-situ air flow test in Essen. Then the coupled model was employed to investigate responses of multiphase flow and soil skeleton deformation to compressed air or freshwater injection using the same simulation conditions in an aquifer of Tianjin, China. The simulation results show that with injecting pressurized fluids, the vertical effective stress in some area decreases owing to the pore pressure increasing, an expansion of soil skeleton appears, and land uplift occurs due to support actions from lower deformed soils. After fluids injection stops, soil deformation decreases overall due to injecting fluids dissipating. With the same applied pressure, changes in multiphase flow and geo-mechanical deformation caused by compressed air injection are relatively greater than those by freshwater injection. Furthermore, the expansion of soil skeleton induced by compressed air injection transfers upward and laterally continuously with time, while during and after freshwater injection, this expansion reaches rapidly a quasi-steady state. These differences induced by two fluids injection are mainly because air could spread upward and laterally easily for its lower density and phase state transition appears for compressed air injection.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.113-119
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• 2022

Sudden intrusion of a large amount of surface water into a flood defensive tunnel or pipeline system can compress the residual air. The compressed air may explode along with water through the inlet or air vent, resulting in hydraulic capacity degradation or safety hazards. This study aims to investigate the behavior of compressed air body in pipelines according to the residual air condition with a series of laboratory experiments measuring pressure variation. It has been found that flow characteristics and residual air conditions have a dominant influence on the magnitude and periodicity of the pressure variation. A proper measure to effectively control the residual air is required for securing the design capacity of flood defensive pipeline systems, since the peak pressure is predominantly affected by residual air conditions.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.395-397
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• 2006

Air interlacing serves to protect the yarn against damage, strengthens inter-filament compactness or cohesion, and ensures fabric consistency. The air interlacing nozzle is used to introduce intermittent nips to a filament yarn so as to improve its performance in textile processing. The effect of various interlacing nozzle geometries on the interlacing process was studied. The geometries of interlacing nozzles with single or multiple air inlets located across the width of yarn channels are investigated. The basis case is the yarn channel, with a perpendicular main air inlet in the middle. Other cases have main air inlets, slightly inclined double sub air inlets, The yarn channel cross sectional shapes are either semicircular or rectangular shapes. The compressed impinging jet from the main air inlet hole hits the opposing bottom wall of the yarn channel, is divided into two branches, joins with the compressed air coming out from sub air inlet at the bottom and creates two free jets at both ends of the yarn channel. The compressed air movement in the cross-section consists of two opposing directional vortices. The CFD-FASTRAN flow parallel solver was used to perform steady simulations of impinging jet flow inside of the interlace nozzles. The vortical structure and the flow pattern such as pressure contour, particle traces, velocity vector plots inside of interlace nozzle geometry are discussed in this pater.

• Korean Journal of Artificial Intelligence
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• v.6 no.1
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• pp.1-10
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• 2018

Compressed Air is an important energy source used in most factories nowadays. The automation trend using air compressor has been gradually increasing with the interest of the 4th industry in recent years. With the air compressor system, it is possible to construct the device at low cost and easily achieve automation and energy saving. In addition, With trend of FA, miniaturation and light weight manufacturing trend expand their use in the electronics, medical, and food sectors. Research method is to design the technology for the remote control of the following information as USN base. Development of flexible sensing module from real time observation module for fusion of IT technology in compressed air systems, design and manufacture of flexible sensing module, and realiability assessment. Design of real-time integrated management system for observation data of compressed air system - Ability to process observation data measured in real time into pre-processing and analysis data. This study expects unconventionally decreasing effect of energy cost that takes up 60~70% of air compressor layout and operation and maintenance management cost through USN(Ubiquitous Sensor Network) technology by using optimum operational condition from real time observation module. In addition, by preventing maintenance cost from malfunction of air compressor beforehand, maintenance cost is anticipated to cut back.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.11-17
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• 2001

• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.50-56
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• 2011

A preliminary experimental study of new concept air hybrid engine, which stores compressed air in the tank during braking and re-use it to propel vehicle during crusing or acceleration, was carried out in this study. A single cylinder engine was modified to realize the concept of air hybrid engine. Independent variable valve lift system was adopted in one of the exhaust valves to store the compressed air into the air tank during compression period. An air injector module was installed in the place of spark plug, and the stored compressed air was supplied during the expansion period to realize air motoring mode. For air compression mode, the tank with volume of 30 liter could be charged up to more than 13 bar. By utilizing this stored compressed air, motoring work of 0.41 bar of IMEP(Indicated mean effective pressure) at maximum can be generated at the 800rpm conditions, which is higher than the case of normal idle condition by 1.1 bar of IMEP.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.3
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• pp.278-283
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• 2013

While Built-in Spindle is working in machining center, the tool is changed by ATC(Automatic Tool Changer) automatically. However, impurities could be stacked in front of spindle because of chips formation while machining, and positional error between spindle and tool could be generated. Compressed air holes are necessary for removal of the impurities. But, the diameter and number of compressed air hole are different for each built-in spindle in market. In this paper, flow analysis is carried out to find out the efficient figuration of the compressed air hole by using velocity and pressure distributions.