• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.643-646
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• 2017

In a liquid rocket engine using hydrocarbon fuels, cooling of the combustion chamber wall is necessary to prevent the combustion chamber wall from melting or structurally deforming due to high heat flux. Among the various methods, regenerative cooling, which uses fuel as a coolant and then injects it into the combustion process, has good performance. This study investigated the heat transfer characteristics of kerosene as a coolant by varying the copper cross-sectional area, the flow rate in the channel, and the current applied to the channel. Convective heat transfer occurred rapidly when the cross-sectional area of the copper channel was small and when the kerosene flow velocity was fast.

• Nuclear Engineering and Technology
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• v.12 no.3
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• pp.153-162
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• 1980

The investigation of the fuel cladding temperature behavior and heat transfer mechanism during the reflooding phase of a LOCA plays an important role in performance evaluation of ECCS and safety analysis of water reactors. Reflooding experiments were performed with horizontal and vertical flow channels to investigate the effect of coolant flow channel orientation on rewetting process. Emphasis was mainly placed on the CANDU reactor which has horizontal pressure tubes in core, and the results were compared with those of vertical channel. Also to investigate the rewetting process visually, the experiments by using a rod in annulus and a quartz tube heated outside were performed. It can be concluded that the rewetting velocity in horizontal flow channel is clearly affected by flow stratification, however, the average rewetting velocity is similar to those in vertical flow channel for same conditions.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.101-104
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• 2007

Mechanical behavior in metal bipolar plate of a fuel cell stack was studied using finite element analysis. The fuel stack is essentially composed of a metal bipolar plate (metal BP), a gasket, an end plate, a membrane electrolyte assembly (MEA), and a gas diffusion layer (GDL). It is important to maintain a suitable fastening force of Metal BP, because it influences the power efficiency of the fuel cell stack. After a gasket and a GDL are placed on the metal BP, the reaction force with the displacement is measured. The channel of metal bipolar plate is replaced by a simple geometrical plate. The results of FEM are similar to those of experiment. Therefore mechanical behavior in metal BP of a fuel cell stack can be estimated by using FEM.

• Membrane Journal
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• v.26 no.1
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• pp.1-13
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• 2016

Fuel cells are regarded as a representative energy source expected to replace fossil fuels particularly used in internal combustion engines. One of the most important components is polymer electrolyte membranes (PEMs) acting as a proton conducting barrier to prevent fuel gas crossover. Since water channels act as proton pathways through PEMs, many researchers have been focused on the 'good phase-separation of hydrophilic moiety' which ensures high water retention under low humidity enough to keep the water channel for good proton conduction. Here, we summarized the strategies which have been adopted to synthesize sulfonated PEMs having high proton conductivities even under low humidified conditions, and hope this review will be helpful to design high performance hydrocarbon PEMs.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.1945-1954
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• 2020

Subchannel code is one of the effective simulation tools for thermal-hydraulic analysis in nuclear reactor core. In order to reduce the computational cost and improve the calculation efficiency, empirical correlation of turbulent mixing coefficient is employed to calculate the lateral mixing velocity between adjacent subchannels. However, correlations utilized currently are often fitted from data achieved in central channel of fuel assembly, which would simply neglect the wall effects. In this paper, the CFD approach based on spectral element method is employed to predict turbulent mixing phenomena through gaps in 3 × 3 bare tight lattice rod bundle and investigate the flow pulsation through gaps in different positions. Re = 5000,10000,20500 and P/D = 1.03 and 1.06 have been covered in the simulation cases. With a well verified mesh, lateral velocities at gap center between corner channel and wall channel (W-Co), wall channel and wall channel (W-W), wall channel and center channel (W-C) as well as center channel and center channel (C-C) are collected and compared with each other. The obvious turbulent mixing distributions are presented in the different channels of rod bundle. The peak frequency values at W-Co channel could have about 40%-50% reduction comparing with the C-C channel value and the turbulent mixing coefficient β could decrease around 25%. corrections for β should be performed in subchannel code at wall channel and corner channel for a reasonable prediction result. A preliminary analysis on fluctuation at channel gap has also performed. Eddy cascade should be considered carefully in detailed analysis for fluctuating in rod bundle.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.1990-1997
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• 2020

To support the safe operation of the Miniature Neutron Source Reactor (MNSR), a thermo-hydraulic transient model using the RELAP5/Mod3.2 code was simulated. The model was verified by comparing the results with the measured and the previously calculated data. The comparisons consisted of comparing the MNSR parameters under normal constant power operation and reactivity insertion transients. Reactivity Insertion Accident (RIA) for three different initial reactivity values of 3.6, 6.0, and 6.53 mk have been simulated. The calculated peaks of the reactor power, fuel, clad and coolant temperatures in hot channel were calculated in this model. The reactor power peaks were: 103 kW at 240 s, 174 kW at 160 s and 195 kW at 140 s, respectively. The fuel temperature reached its maximum value of 116 ℃ at 240 s, 124 ℃ at 160 s and 126 ℃ at 140 s respectively. These calculation results ensured the high inherently safety features of the MNSR under all phases of the RIAs.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.72-77
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• 2010

During the period of reinforcement work for the licensing renewal of CANDU NPP, the fuel channels, Calandria tubes and feeders of CANDU Reactor are replaced. The remote visual inspection of Calandria internal is also performed during the period of reinforcement work. This period is a unique opportunity to inspect the inside of the Calandria. The visual inspection for the Calandria vessel and its internals of Wolsong NPP Unit 1 was performed by Nuclear Engineering & Technology Institute(NETEC) of KHNP. To perform this inspection, NETEC developed equipment applied new technology such as the synchronization of 3D CAD, automatic alignment and control system. The inspection confirmed that the Calandria integrity of Wolsong NPP Unit 1 is perfect.

• Journal of Electrochemical Science and Technology
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• v.10 no.4
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• pp.345-360
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• 2019

Polymer Electrolyte Membrane Fuel Cells (PEMFC) is one of the leading advanced energy conversion technology for the use in transport. It generates water droplets through the catalytic processes and dispenses the water through the gas-flowed microchannels. The droplets in the dispensing microchannel experience g-forces from different directions during the operation in transport. Therefore, this paper reviews the computational modelling topics of droplet dynamics behaviour specifically for three categories, i.e. (i) the droplet sliding down a surface, (ii) the droplet moving in a gas-flowed microchannel, and (iii) the droplet jumping upon coalescence on superhydrophobic surface; in particular for the parameters like hydrophobicity surfaces, droplet sizes, numerical methods, channel sizes, wall conditions, popular references and boundary conditions.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.542-545
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• 2008

Experiments have been performed to investigate effects of pulsating cathode flow on a 10-cell proton exchange membrane fuel cell (PEMFC) stack. For all the experiments, the flow rate, temperature and relative humidity of hydrogen at the anode inlet are fixed. The effects of the pulsating frequency, amplitude and flow rate at the cathode inlet on performance of 10-cell PEMFC are examined. The polarization and power curves show that the power output and limiting current is substantially increased when the pulsating component is added to cathode flow channel. The maximum power output increases by up to 38% and enhancement of the overall performance is more pronounced at lower flow rate region.

• 한국연소학회:학술대회논문집
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• 2000.05a
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• pp.162-168
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• 2000

This paper conducted experimental study of turbulent diffusion flame, equipped with a unique double swirler combustor for gas fuel. The burner has two vane swirlers which are fitted to primary, secondary air channel. Temperature, and NOx emission concentrations are measured in combustion flame region and velocity in cold flow for various primary/secondary air ratio conditions. The results showed the characteristics of swirl flame and decreasing NOx concentrations with increasing primary/secondary air ratio.