• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2004-2006
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• 1999

In this paper, double Cylindrical type ozonizer has been designed and manufactured to improve ozone yield by cooling external electrode. The ozonizer equipped with three electrodes ( central, internal and external electrodes ). Discharge and ozone characteristics are described in this paper by varying the flow rate( Q ) of oxygen supplied gas, temperature of cooling gas and supplied voltage.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.282-291
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• 1998

Heat transfer performance are studied for the turbulent flow of water in 3 smooth tube coils having ratios of coil to tube diameter of 16, 21 and 27, and a corrugated-coiled tube having a ratio of coil to tube diameter of 29, for Reynolds numbers from 8000 to 60000 and is also compared with the limited results available to data. The experiments are carried out for the fully developed turbulent flow of water in tube coils under the condition of uniform heat flux. This work is limited 0 tube coils of R/a between 10 and 30. The tube having a ratio of coil to tube diameter of 27 among the 3 smooth tube coils shows the best heat transfer performance. The performance of coiled tube best transfer performance. The performance of coiled tube with a similar curvature ratio is better for a corrugated-coiled tube(R/a=17) than for a smooth coiled tube(R/a=16). An empirical relation which correlates most of the data within $\pm$25% was also developed. Test result shows that the Nusselt number is found to be affected by a secondary flow due to curvature.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.897-907
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• 2020

The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.685-691
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• 2005

In this study, high performance waste heat recovery heat exchanger was developed using the bayonet tube with spiral serrated fins. Especially, heat exchanger of the bayonet tube type was operated well because of double water passes mechanism and characteristics. A cooling water Passes down inner tubes to thimble-form tubes, then flows back up as it boils. The heat exchanger of bayonet tube type was composed of steel tube with 7channels$(I.D_1\;14mm.\;I.D_2\;31.6mm)$ and spiral serrated fins. The performance tests were conducted under the following conditions A cooling water flow rate was 273kg/h and engine l·pm was varied from 750rpm to 3500 rpm. From the experimental result. waste heat recovery was 9.21kW when engine rpm was 3500. and pressure drop was $15\~260mmHg/m^3$ The effectiveness of heat exchanger was about /$0.7\~0.9$. The performance of heat exchanger was evaluated by using the $\varepsilon-NTU$ method. In the study the NTU of the heat exchanger was $1.57\~2.33$.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.38.1-38.1
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• 2014

A non-axisymmetric mass distribution in the galactic bulge (or bar) causes gas flow from the disk to the nuclear region, inducing intense star formation in the nucleus. We investigate the relation between the ellipticity of the bulge and the presence of a nuclear starburst by using a volume-limited sample of galaxies. We use 1,680 spiral galaxies with Mr < -19.5 at 0.02 <= z < 0.05 in the Sloan Digital Sky Survey Data Release 7. We find that the occurrence of nuclear starburst has a moderate correlation with bulge ellipticity in intermediate-type spiral galaxies (morphology classes Sab~Sb) in low galaxy number density environments. In high galaxy number density environments, close encounters and mergers between galaxies can cause gas inflow to the nuclear region even without the presence of non-axisymmetric bulges.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1703-1708
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• 2004

In this study, we are investigated experimentally the pumping characteristics about the pumping channel shapes of disk-type drag pump (DTDP). We are experimented the pumping performance about the rotors which have channel or do not exist. The channel disk-type rotor has spiral channels both upper and lower part, and stator is planar. The planar disk-type rotor hasn't channel and stator has spiral channels both upper and lower part. The flow-meter method is adopted to calculate the pumping speed. Compression ratio and pumping speeds for the nitrogen gas are measured under the inlet pressure range of 0.001 ${\sim}$ 4 Torr. The maximum of compression ratio was about 3300 for three-stage DTDP (channel disk-type rotor), 1000 for four-stage (planar disk-type rotor) and two-stage DTDP (channel disk-type rotor) at zero throughput. The ultimate pressure was $1.6{\times}10^{-6}$ Torr for three-stage DTDP (channel disk-type rotor), $2.5{\times}10^{-6}$ Torr for four-stage DTDP (planar disk-type rotor).

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.71-75
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• 2010

The efficient performance of absorber is of great importance for the absorption heat pump cycle. The experimental study of absorber with spiral tube of tangential feeding of liquid phase has been investigated using methanol-glycerine as a working fluid. The effect of change in absorber operating conditions was analyzed to improve the performance. The increase in solution flow rate and cooling flow rate positively affects the absorber performance while an increse in the solution concentration negatively affects the absorber performance. The results showed that mass absorption flux was in the range of $0.2{\sim}0.6kgm^{-2}sec^{-1}$, the solution heat transfer coefficient between 1.6 and $4.2kwm^{-2}K^{-1}$, the absorber thermal load from 0.9 to 1.5kw and the mass transfer coefficient from 0.9 to 1.7 m/sec.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.35-40
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• 2015

Centrifugal pumps consume considerable amounts of energy in various industrial applications. Therefore, improving the efficiency of pumps machine is a crucial challenge in industrial world. This paper presents numerical investigation of flow characteristics in volutes of centrifugal pumps in order to compare the energy consumption. A wide range of volumetric flow rate has been investigated for each case. The standard k-${\varepsilon}$ is adopted as the turbulence model. The impeller rotation is simulated employing the Multi Reference Frames(MRF) method. First, two different conventional design methods, i.e., the constant angular momentum(CAM) and the constant mean velocity (CMV) are studied and compared to a baseline volute model. The CAM volute profile is a logarithmic spiral. The CMV volute profile shape is an Archimedes spiral curve. The modified volute models show lower head value than baseline volute model, but in case of efficiency graph, CAM curve has higher values than others. Finally for this part, CAM curve is selected to be used in the simulation of different cross-section shape. Two different types of cross-section are generated. One is a simple rectangular shape, and the other one is fan shape. In terms of different cross-section shape, simple rectangular geometry generated higher head and efficiency. Overall, simulation results showed that the volute designed using constant angular momentum(CAM) method has higher characteristic performances than one by CMV volute.

• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.202-206
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• 2007

The adhesion of Campylobacter jejuni to chicken skin, along with the associated morphological changes under aerobic conditions at 4, 25, and $37^{\circ}C$ and microaerobic ($O_2\;5%,\;CO_2\;10%,\;N_2\;85%$) conditions, were investigated using confocal laser scanning microscopy (CLSM), flow cytometry, and plate counting. The morphological change of C. jejuni from a spiral shape to a coccoid form or VBNC form (viable but nonculturable form) progressed rapidly under aerobic conditions at 25, 37, and $4^{\circ}C$. As regards adhesion, the C. jejuni cells were mostly located in the crevices and feather follicles of the chicken skin, where the cells in the feather follicles floated freely in the entrapped water, even after the skin was rinsed quite thoroughly. CLSM also revealed the penetration of some spiral-shaped C. jejuni cells into the chicken skin. Even after changing their shape at various temperatures, coccoid-form C. jejuni cells were still found in the crevices and feather follicles of the chicken skin.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.253-261
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• 1987

Thermoacoustic oscillation of an air column induced by heated wires is investigated analytically and experimentally. Acoustic power generation from a single heater wire is estimated based on the result of heat transfer analysis and expressed in terms of the efficiency factor indicating the conversion efficiency from heat to acoustic energy. It is shown that the efficiency factor becomes maximum when the wire radius is the order of the coustic boundary layer thickness and the flow velocity is close to the thermal diffusion velocity. Onset condition of the column oscillation is obtained by equating the acoustic power generation at the heater to the power loss due to thermoviscous dissipation at the tube wall and the convection and radiationloss at the open ends of the tube. In estimating the acoustic power generation, the heater is treated as a stretched single wire by correcting the flow velocity to take into account the interactions between adjacent heater wires. Experiment is performed by using a spiral heater of 1mm diameter in an air column of 37mm diameter. The heat input to drive the oscillation is measured and compared with the theoretical prediction. A good agreement is found between the theory and experiment, which is regarded as a substantial verification of the present analysis.