• Journal of Mechanical Science and Technology
• /
• v.20 no.3
• /
• pp.391-398
• /
• 2006

This work involves a method for modeling the flow distribution in the stack of a solid oxide fuel cell. Towards this end, a three dimensional modeling of the flow through a Solid Oxide Fuel Cell (SOFC) stack was carried out using the CFD analysis. This paper examines the efficacy of using cold flow analysis to describe the flow through a SOFC stack. It brings out the relative importance of temperature effect and the mass transfer effect on the SOFC manifold design. Another feature of this study is to utilize statistical tools to ascertain the extent of uniform flow through a stack. The results showed that the cold flow analysis of flow through SOFC might not lead to correct manifold designs. The results of the numerical calculations also indicated that the mass transfer across membrane was essential to correctly describe the cathode flow, while only temperature effects were sufficient to describe the anode flow in a SOFC.

• Journal of the Korean Electrochemical Society
• /
• v.9 no.4
• /
• pp.170-177
• /
• 2006

Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.5
• /
• pp.557-565
• /
• 2022

The effect of flow configuration in ammonia-fed solid oxide fuel cell are investigated by using a three-dimensional numerical model. Typical flow configurations including co-flow and counter-flow are considered. The ammonia is directly fed into the stack without any external reforming process, resulting in an internal decomposition of NH3 in the anode electrode of the stack. The result showed that temperature profile in the case of counter-flow is more uniform than the co-flow configuration. The counter-flow cell, the temperature is highest at the middle of the channel while in the case of co-flow, the temperature is continuously increased and reached maximum value at the outlet area. This leads to a higher averaged current density in counter-flow compared to that of co-flow, about 5%.

• Journal of computational fluids engineering
• /
• v.14 no.2
• /
• pp.59-67
• /
• 2009

An accurate prediction of the bypass flow is of great importance in the VHTR core design concerning the fuel thermal margin. Nevertheless, there has not been much effort in evaluating the amount and the distribution of the core bypass flow. In order to evaluate the behavior and the distribution of the coolant flow, a unit-cell experiment was carried out. Unit-cell is the regular triangular section which is formed by connecting the centers of three hexagonal blocks. Various conditions such as the inlet mass flow rate, block combinations and the size of bypass gap were examined in the experiment. CFD analysis was carried out to analyze detailed characteristics of the flow distribution. Commercial CFD code FLUENT 6.3 was validated by comparing with the experimental results. In addition, SST model and standard k-$\varepsilon$ model were validated. The results of CFD simulation show good agreements with the experimental results. SST model shows better agreement than standard k-$\varepsilon$ model. Results showed that block combinations and the size of the bypass gap have an influence on the bypass flow ratio but the inlet mass flow rate does not.

• Transactions of the Korean hydrogen and new energy society
• /
• v.20 no.4
• /
• pp.283-290
• /
• 2009

This study focuses on the performance characteristics of polymer electrolyte membrane fuel cell (PEMFC) using the AC impedance technique. The experiment was carried out to investigate the optimal operating conditions of PEMFC such as cell temperature, flow rate, humidified temperature and back-pressure. The fuel cell performance was analyzed by DC electronic-loader with constant voltage mode and expressed by voltage-current density. Additionally, AC impedance was measured to analysis of ohmic and activation loss and expressed by Nyquist plot. The results showed that the cell performance increased with increase of cell temperature, air flow rate, humidified temperature and backpressure. Also, the activation loss decreased as the increase of cell temperature, air flow rate, humidified temperature and backpressure.

• YAKHAK HOEJI
• /
• v.47 no.6
• /
• pp.345-351
• /
• 2003

Heptaplatin, cis-Malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolane]platinum(II), is a novel platinum-based antitumor agent with clinical potential against human stomach cancer and the 3rd generation of the cisplatin. This study was performed to study how cisplain, heptaplatin and sunpla which is a mixture of heptaplatin and mannitol (w: w=l : 2) affect cell viability of SK-MEL-28 human melanoma cell line. Heptaplatin ($IC_{50}$/; 95.35 $\mu$M) and sunpla ($IC_{50}$/; 10.95 11M) were less effect than cisplatin (IC $_{50}$; 10.92 $\mu$M) on the SK-MEL-28 cells. By cell cycle analysis using flow cytometry, it was identified that the cells were arrested at G2/M phase by cisplatin, heptaplatin and sunpla, and percentage of cell death group was increased according to increasing of time and concentration. These results suggest that cisplatin, heptaplatin and sunpla are a novel anticancer agent against human melanoma cell.l.

• Toxicological Research
• /
• v.14 no.2
• /
• pp.143-149
• /
• 1998

This study was carried out to evaluate the testicular toxicity of 2-bromopropane (2-BP), which recently caused occupational intoxication on the reproductive and hematopoietic system in Koreans, using light microscopy, immunohistochemistry and flow cytometry. 10 weeks old male Sprague-Dawley (SD) rats were treated with 0.5 g/㎏/day of 2-BP orally for 8 consecutive weeks. The testes of the rats were vascularly perfused with Karnovsky's solution or immersed in Bouin's solution, embedded in plastic and evaluated with light microscopy. And relative proportions of haploid, diploid, and tetra-ploid states of DNA ploidy in the testicular cell suspensions of the SD rats were examined by flow cytometry. 2-BP induced severe testicular atrophy, depletion and degeneration of spermatogonia, spermatocytes, and spermatids and mild hyperplasia of Leydig cells without significant morphological changes. The Leydig cell hyperplasia was confirmed by immunohistochemistry using proliferating cell nuclear antigen (PCNA). The immunopositive cells against PCNA were observed in the nuclei oj some interstitial cells. Relative proportions of haploid states of DNA ploidy decreased in the atrophic testicular cell suspensions comparing with those of the control. In conclusion, 2-BP induced testicular atrophy with Leydig cell hyperplasia as examined by histopathology, immunohistochemistry and DNA flow cytometry.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.45-48
• /
• 2008

This paper presents a passive air-breathing direct methanol fuel cell (DMFC) which has been designed and tested. The single cell is fuelled by methanol vapor that is supplied through flow channel from a methanol reservoir at the anode, and the oxygen is supplied via natural air-breathing at the cathode. The methods for supplying the methanol vapor to the single cell were parallel channel and chamber. This research investigates various methods to identify the effects of using flow channels for providing the methanol vapor at the anode, and the opening ratio between the inlet and outlet ports for the methanol flow at the anode. The best flow channel condition for passive DMFC was a chamber, and the opening ratio was 0.8. Under these conditions, the peak power was 10.2mW/$cm^2$ at room temperature and ambient pressure. The key issues for the Passive DMFCs for using methanol vapor are that sufficient methanol needs to be supplied using a large as possible opening ratio. However, it is shown that the performance of the passive DMFC, which has a channel at the anode,is low due to the low differential pressure and insufficient methanol supply rate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.7
• /
• pp.662-666
• /
• 2005

Silicon nitride $(SiN_x)$ film is a promising material for anti-reflection coating and passivation of multicrystalline silicon (me-Si) solar cells. In this work, a plasma-enhanced chemical vapor deposition (PECVD) system with batch-type reactor tube was used to prepare highly robust $SiN_x$ films for screen-printed mc-Si solar cells. The Gas flow ratio, $R=[SiH_4]/[NH_3]$, in a mixture of silane and ammonia was varied in the range of 0.0910.235 while maintaining the total flow rate of the process gases to 4,200 sccm. The refractive index of the $SiN_x$ film deposited with a gas flow ratio of 0.091 was measured to be 2.03 and increased to 2.37 as the gas flow ratio increased to 0.235. The highest efficiency of the cell was $14.99\%$ when the flow rate of $SiH_4$ was 350 sccm (R=0.091). Generally, we observed that the efficiency of the mc-Si solar cell decreased with increasing R. From the analysis of the reflectance and the quantum efficiency of the cell, the decrease in the efficiency was shown to originate mainly from an increase in the surface reflectance for a high flow rate of $SiH_4$ during the deposition of $SiN_x$ films.

• 한국전산유체공학회:학술대회논문집
• /
• 2007.10a
• /
• pp.232-235
• /
• 2007

A comprehensive numerical study was carried out to identify the on-set condition of the cell structures of oblique detonation waves (ODWs). Mach 7 incoming flow was considered with all other flow variables were fixed except the flow turning angles varying from 35 to 38. For a given flow conditions theoretical maximum turning angle is $38.2^{\circ}$ where the oblique detonation wave may be stabilized. The effects of grid resolution were tested using grids from $255{\times}100$ to $4,005{\times}1,600$. The numerical smoked foil records exhibits the detonation cell structures with dual triple points running opposite directions for the 36 to 38 turning angles. As the turning angle get closer to the maximum angle the cell structures gets finer and the oscillatory behavior of the primary triple point was observed. The thermal occlusion behind the oblique detonation wave was observed for the $38^{\circ}$ turning angle.