• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.263-271
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• 2006

In this study, $20\;Nm^3/hr$ scale compact hydrogen generator which can be apply to the hydrogen station was manufactured and tested. The design of $20\;Nm^3/hr$ scale compact hydrogen generator was upgraded on the base of $5\;Nm^3/hr$ scale plate hydrogen generator concept stacking the plate reactors. Ideas for improving system efficiency such as heat recovery from the exhaust, exhaust duct which is especially design for plate type reactor, reinforcement of insulation, enlargement of heat exchange area of reactor, introduction of desulphurizer reactor and PROX rector in a compact design etc. were applied. From the performance test, we can learn that the $20\;Nm^3/hr$ scale compact hydrogen generator can be operated steadily at 100% road condition and the methane conversion of over 94%(at S/C=3.75) was obtained. This result shows that the concept of plate type hydrogen generator can be scale-up to the $20\;Nm^3/hr$ scale and fit for hydrogen generator for on site hydrogen station application.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.125-130
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• 2008

The present study numerically simulates the flow and heat transfer characteristics of rib-induced secondary flow in a cooling channel with staggered V-shaped ribs, extruded on both walls. The rib pitch-to-height ratio (p/h) varies from 2.8 to 10 with the rib-height-to-hydraulic diameter ration ($h/D_h$) of 0.07 and the Reynolds number of 50,000. Shear stress transport (SST) turbulence model is used as a turbulence model. Computational results show that complex secondary flow patterns are generated in the duct due to the snaking flow in the streamwise direction for all tested cases. In the range of p/h=5 to 10 the staggered V-shaped rib gives about 3 times higher heat transfer augmentation than the reference smooth channel with high heat transfer on both front side and the area around the leading edge of the ribs, while the former cases give about 2.5 times higher streamwise pressure drop than the latter ones. Consequently, for the thermal performances, based on the equal pumping power condition, the staggered ones give about 2 times higher values than the latter ones with more uniform heat transfer distribution.

• 동력기계공학회지
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• 제20권6호
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• pp.80-86
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• 2016

In this study, The watertight damper was designed to improve conventional DN 350A butterfly valve. The FSI(Fluid-Structure Interaction) analysis has performed to investigate the safety factor for the watertight damper. When watertight damper of disk was closed, the disk of pressure value is constant. However depending on the opening angle of disk, the flow velocity and pressure are changed. The maximum velocity was appeared at the end of disk on the small outlet area of duct. When the opening angel of disk is $90^{\circ}$, the maximum velocity was appeared at the center of ending disk. So we were found the opening angle of disk is bigger, the flow rate is increased and velocity is also increased from the result of FSI analysis. We can find the least deformation and stress when the opening angel of damper is $90^{\circ}$. When the $45^{\circ}$ opening angle of disk, the largest deformation and stress was found and the minimum safety factor 1.3 was calculated. As a result, we found that the structure of watertight damper is safe enough irrespective of opening angel.

• 대한기계학회논문집B
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• 제24권8호
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• pp.1128-1138
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• 2000

Pumping action in ejector systems is generally achieved through the mixing of a high-velocity and high-energy stream with a lower-velocity and lower-energy stream within a duct. The design and performance evaluation of the ejector systems has developed as a combination of scale-model experiments, empiricism and theoretical analyses applicable only to very simplified configurations, because of the generic complexity of the flow phenomena. In order to predict the detailed performance characteristics of such systems, the flow phenomena throughout the operating regimes of the ejector system should be fully understood. This paper presents the computational results for the two-dimensional supersonic ejector system with a second throat. The numerical simulations are based on a fully implicit finite volume scheme of the compressible Reynolds-averaged Navier-Stokes equation in a domain that extends from the stagnation chamber to the diffuser exit. For a wide range of the operating pressure ratio the flow field inside the ejector system is investigated in detail. The results show that the supersonic ejector systems have an optimal throat area for the operating pressure ratio to be minimized.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.1083-1090
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• 2005

Repeated ribs are used on heat exchange surfaces to promote turbulence and enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concern detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue is tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall have a 45$^{\circ}$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increase with increasing the number of rough walls.

• 동력기계공학회지
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• 제9권1호
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• pp.30-35
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• 2005

Repeated ribs are used on heat exchanger surfaces to promote turbulence and to enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concerns detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue was tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall had a $45^{\circ}$ inclined square rib. Uniform heat flux was maintained on the whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increased with increasing the number of rough walls.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2011년도 춘계학술논문발표회 논문집
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• pp.9-15
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• 2011

This study aims to validate predictive capabilities of FDS for the pool fire in three rooms connected to ventilation network. The three rooms in real scale fire test facility are configured to be similar to that of nuclear power plant in size, ventilation condition, construction material, etc. Basically three rooms are confined to the other area except two open doors and two ventilation duct in each room. The real scale fire test was conducted with these conditions and the predictive capabilities of FDS will be validated by comparing FDS simulation results with experimental data from the temperature, heat flux, and concentration point of view. This study concludes that temperature from FDS is about 25 % lower deviation from the experiment, and heat flux from FDS is about 5% deviation.

• 대한핵의학회지
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• 제2권1호
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• pp.21-25
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• 1968

Radiographic visualization of the pancreas is a difficult problem, but the direct visualization of the pancreas is possible by the injection of the amino-acid methionine tagged with $selenium^{75}$75 ($Se^{75}$). In order to know the diagnostic value of pancreas scanning, scans were performed on 23 cases using $selenium^{75}$-selenomethionine. These cases were also given egg white, probanthine and morphine. 1. Good visualization of the pancreas scanning was observed on 19 cases, presumably with normal pancreas. 2. A case which showed diffusely decreased uptake on pancreas scanning was proven to have lesions in the bile duct and the gall bladder. 3. Of those two cases which showed localized cold area, one had pancreas cyst and the other one was not explored. 4. A case which showed no visualization of the pancreas was proven to have pancreatic carcinoma. 5. Two cases which showed widened duodenal loop by upper gastro-intestinal series revealed normal pancreas scanning, and no pancreatic disease was found in both cases.

• 한국유체기계학회 논문집
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• 제18권3호
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• pp.33-37
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• 2015

A numerical study on the IPM/Bridge Diode cooling and coil cooling has been performed. Results are presented as plots of thermal resistance, temperature drop and RPM-ratio. CFD analysis for conventional cooling system has been performed as a reference case. As the RPM-Ratio was increased, heatsink thermal resistance and coil temperature were decreased. IPM/Bridge Diode thermal resistance and temperature of the coil is tended to be trade-off. The temperature of coil closest to the AC-motor fan showed the most significant change in accordance with duct design. The temperature of coil located at the top of DC-motor fan showed the most significant variation as the cooling air passes the heatsink fin area.

• 대한기관식도과학회지
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• 제4권2호
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• pp.188-192
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• 1998

Background and Objectives： The most common cause of the failure of endoscopic dacryocystorhinostomy is closure of the osteotomy site due to granulation or adhesion. We used mitomycin-C, an antineoplastic antibiotic agent, soaking over the osteotomy site to suppress fibrous proliferation and scar formation during the endoscopic dacryocystorhinostomy. Materials and Methods : A total of 20 Patients diagnosed with nasolacrimal duct obstruction were assigned randomly to either a mitomycin-C group or a control group. Endoscopic dacryocystochinostnmy has been used in both groups. In the mitomycin-C group, a piece of merocel soaked with 0.2 mg/ml mitomycin-C was applied to the osteotomy site and then after 30 minutes was removed. Results : All patients in the mitomycin-C group remained symptom free after removal of their silicone tube (100% success), and there were two patients in the control group who had recurrent epiphora (67% success). In the mitomycin-C group, the average surface area of the osteotomy at the end of the sixth postoperative month was 4.1 $\textrm{mm}^2$, whereas that of the control group was 2.5 $\textrm{mm}^2$. Neither serious systemic nor local toxicity were noted in the mitomycin-C group. Conclusion : Intraoperative mitomycin-C may possibly improve success rates over the endoscopic dacryocystorhinostomy procedure.