• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.620-623
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• 2013

The carbon nanotube / poly-vinylidene fluoride (CNT/PVDF) composite films for the nano-generator devices were fabricated by spray coating method using the CNT/PVDF solution, which was prepared by adding PVDF pellets into the CNT dispersed N-Methyl-2-pyrroli-done (NMP) solution. The flexible CNT/PVDF composite films were investigated by the scanning electron microscopy, which revealed that the CNTs were uniformly dispersed in the PVDF matrix and thickness of the films was approximately $20{\mu}m$. Fourier transform infra-red spectra were used to investigate crystal structure of the as-spray-coated CNT/PVDF films, and we found that they revealed extremely large portion of the ${\beta}$ phase PVDF. The capacitance of the CNT/PVDF films increased by adding CNTs into the PVDF matrix, and finally saturated. However, the resistance didn't show any saturation effect in the CNT concentration range of 0~4 wt%. Finally, the resulting nano-generator devices revealed reasonable current output after given mechanical stress.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.82-87
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• 2015

A nozzle with vortex generator was used to develop the low pressure nozzle with high atomization performance and the nozzle atomized the liquid by centrifugal shear forces. In order to analyze the atomization characteristics, a shadowgraphy method was used and the measurement of droplet size was performed by using laser diffraction analyzer. The liquid injection pressure was fixed as 0.03 bar which is very low pressure and the gas injection pressures were changed from 0 bar to 2.0 bar. As a result, the breakup was achieved at the air injection pressure of 0.25 bar and over. The nozzle with the orifice diameter of 0.4 mm and the orifice gap of 0.25 mm presented small droplet diameters under 50 at the air injection pressure of 0.75 bar.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.2
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• pp.55-63
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• 2013

For a large-scale semiconductor manufacturing clean room, the energy consumed in an outdoor air conditioning system to heat, humidify, cool and dehumidify incoming outdoor air is very large. In particular, the energy requirement to humidify outdoor air in the winter season is generally known to be high. Recently, in order to overcome the high energy consumption nature of a steam generator in a conventional steam humidification type outdoor air conditioning system, an air washer is often introduced instead of the steam generator in the outdoor air conditioning system, which can be called a water spray humidification type outdoor air conditioning system. Therefore, the assessment and comparison of the annual energy consumed in the steam humidification type and the water spray humidification type outdoor air conditioning systems deserves to be examined in order to reduce the outdoor air conditioning load of a clean room. In the present study, a numerical analysis was conducted to obtain the annual electric power consumption of the two outdoor air conditioning systems. It was shown from the comparison of the numerical results that the water spray humidification type outdoor air conditioning system can reduce about 30% of annual electric power consumption of the steam humidification type outdoor air conditioning system.

• The Journal of the Korea Contents Association
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• v.10 no.10
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• pp.68-77
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• 2010

In the case of operating steam generators for long periods in nuclear power plants, sludge is accumulated inside the steam generator. This phenomenon could adversely affect the operation of the steam generator. This paper is about the design of a sludge washing apparatus which can remove the sludge efficiently and the control methods of the apparatus. In this paper, to design the sludge washing apparatus, firstly, we design nozzles for spraying high-pressure water through applying mathematical models and lab tests. Secondly, we establish the mathematical theory for performance parameters required to drive the sludge washing apparatus. Thirdly, we design physical structures of the apparatus based on the established performance parameters. Finally, we present the control methods of the apparatus. The sludge washing apparatus presented in this paper moves along the walls of the steam generator according to cracks in the tube array, and spray the high pressure water to remove the sludge. By this way, a relatively large amount of sludge formed in the inner surfaces can be washed very effectively.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.235-242
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• 2006

Spray pyrosysis is a process to prepare particles and films by evaporating and decomposing droplets of precursor solutions in the order of 1-10 micrometer in diameter. Key elements of the spray pyrolysis process include precursor, solvent, droplet generator, and reactor. Various combination of these 4 elements produces wide range of particles and films. In general. the current status of the spray pyrolysis technology is not quite promising for commercial success. However, this process will be feasible to produce multicomponent functional materials of controlled morphology. In this paper, current status of the spray pyrolysis technology is introduced with the emphasis of production of fluorescence particles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.62-68
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• 2005

An injector for fuel rich gas generator was designed and experimentally investigated. Five variations of F-O-F triplet impinging type injector were tested to evaluate spray characteristics with kerosene/water simulant propellant. Test was focused to find the effect of design variables of impinging angle, and impinging distance, on the atomization performance. A mixing efficiency is used to compare droplet distribution and local O/F ratio of each injector in the range of momentum ratio of 0.2~1.3. Test results shows the max value of mixing efficiency locates about the 0.8 in momentum ratio. And the injector with an impinging angle of 45 degree and impinging distance of 6mm shows the very good performance result suitable for fuel rich gas generator. A combustion test will be also conducted with selected injector to verify the spray pattern and mixing efficiency.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.107-116
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• 1991

Fine $PbTiO_3$ Particles were synthesized from the $Pb(NO_3)_2$and $TiO(NO_3)_2$ solution by the spray pyrolysis method using the ultrasonic vibrator as a mist generator. The obtained particles were characterized. The mechanisms of particle formation were discussed in comparison with those if other particles, such as $BaTiO_3$, $ZnO_2$, ZnO ....., in the same spray pyrolysis process.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.1
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• pp.1-8
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• 1994

This study carried out to investigate the spray characteristics of diesel oil through out ultrasonic fuel supply system in comparison with conventional. Size of the droplets comprising diesel spray was measured by immersed liquid method at different positions along the spray axis. Droplets distribution diagram was ploted and Sauter Mean Diameter(SMD) was also calculated. The effects of the ultrasonic vibration and injection pressure on the droplet size distribution and SMD were investigated. As the ultrasonic vibration supply SMD decreases on the same injection pressure conditions with conventional injector's. But the effect of ultrasonic vibration decreases with injection pressure increasing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.1-7
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• 2017

The atomization of a liquid into multiple droplets has many important industrial applications, including the atomization of fuels in combustion processes and coating of surfaces and particles. Ultrasonic atomizing nozzle has a transducer that receives electrical input in the form of a high frequency signal from a power generator and converts that into mechanical energy at the same frequency. Liquid is atomized into a fine mist spray using high frequency sound vibrations. In coating applications, the unpressurized, low-velocity spray reduces the amount of overspray significantly because the droplets tend to settle on the substrate, rather than bouncing off it. The spray can be controlled and shaped precisely by entraining the slow-moving spray in an ancillary air stream using specialized types of spray-shaping equipment. The desired patterns of spray can be obtained using an air stream. To simulate the water mist behavior of an ultrasonic atomizing nozzle using an air stream, the Lagrangian dispersed phase model was employed using the commercial code FLUENT. The effects of the nozzle contraction shape, water droplet size and the pneumatic pressure drop on the spray characteristics were investigated to obtain the optimal condition for coating applications.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.2
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• pp.155-160
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• 2004

Water jet trajectories and velocity deficits from a high pressurize nozzles were experimentally observed. In this article, several parameters affecting plugging and erosion onto the steam generator tube were quantitatively analyzed. Visualization, velocity distribution, and spray growth rate with different nozzle configurations have been mainly focused using a 2-D PDPA (Phase Doppler Particle Analyzer) system. The results indicated that trajectories along the centerline regardless of their momentum has its potential core region. However, the phenomena from the peripheral part need to be meticulosly considered. Accordingly, it is evident that quantitative velocity deficits at the outer region are outstanding due to the aerodynamical drag and entrainment.