• Transactions of the Korean hydrogen and new energy society
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• v.34 no.1
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• pp.17-25
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• 2023

The purpose of this study was to propose a design that shows optimal performance by changing the geometry of the internal flow path of the receptacle in order to prevent the decrease in flow rate and differential pressure performance due to the application of the receptacle in the hydrogen charging system. To achieve this, 3D computational fluid dynamics simulation was performed for the receptacle, according to the geometry of the flow path inside the receptacle. The pressure results at the inlet and outlet were measured the same as both of N and H₂ in the experiment, and the flow rate of H₂ was 3.75 times higher than that of N₂. In addition, since the flow performance of the receptacle improved under conditions where the flow path was widened, it was confirmed that reducing the diameter of the poppet and the width of the guide are advantageous for improving performance.

• Journal of the Korean Institute of Gas
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• v.27 no.1
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• pp.38-47
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• 2023

In the hydrogen filling process, hydrogen flows by the pressure difference between the supply pressure at a filling station and a storage tank in the vehicle, and the flow rate depends on the pressure difference. Therefore, it is essential to consider the pressure drop of hydrogen occurring during the filling process, and the efficiency of the hydrogen filling process can be improved through its analysis. In this study, the pressure drop was analyzed for a hose, a nozzle/receptacle coupling, a pipe, and a valve in a filling line. The pressure drops through hose and pipe, the nozzle,receptacle coupling, and the valve were calculated by using a equation for a straight conduit, a flow nozzle formula, and a gas flow respectively. In addition, as a result of comprehensive analysis of the pressure drop effect occurring in each component, it was found that the factor that has the greatest influence on the pressure drop in the entire filling line is the pressure drop through the valve. This study can be used to develop a model of the hydrogen filling process by analyzing hydrogen flow including hydrogen filling in the future.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.4
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• pp.350-357
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• 2023

In this study, the experimental investigation and theoretical analysis were conducted to verify the cooling capacity of the cryocooler used for pre-cooling of hydrogen gas. The effect of the flow rate on a copper pipe attached to the bottom of the cryocooler, which has a coil shape in a hydrogen line, was investigated. Temperature sensors were strategically placed at various positions on the cryocooler to analyze the temperature variations with respect to the flow rate. In this study, the thermal properties of hydrogen for the pressure and temperature were utilized using REFPROP to analyze the cooling capacity of the cryocooler. Based on the experimental results derived from this study, the cooling capacity of the cryocooler for pre-cooling hydrogen gas was considered by calculating the cooling temperature according to the flow rate through theoretical analysis.

• Journal of the Semiconductor & Display Technology
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• v.15 no.4
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• pp.46-50
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• 2016

In this study, we have investigated the effect of the substrate temperature and hydrogen flow rate on the characteristics of IGZO thin films for the TCO(transparent conducting oxide). For this purpose, IGZO thin films were deposited by RF magnetron sputtering at room temperature and $300^{\circ}C$ with various $H_2$ flow rate. In order to investigate the influences of the hydrogen, the flow rate of hydrogen in argon mixing gas has been changed from 0.1sccm to 1.0sccm. IGZO thin films deposited at room temperature show amorphous structure, whereas IGZO thin films deposited at $300^{\circ}C$ show crystalline structure having an (222) preferential orientation. The electrical resistivity of the amorphous-IGZO films deposited at R.T. was lower than that of the crystalline-IGZO thin films deposited at $300^{\circ}C$. The increase of electrical resistivity with increasing substrate temperature was interpreted in terms of the decrease of the charge carrier mobility. The transmittance of the IGZO films deposited at $300^{\circ}C$ was decreased deposited with hydrogen gas.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.98-103
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• 2010

In order to develop two-stroke free-piston hydrogen engine to obtain high thermal efficiency and low emission, backfire occurrence have to be prevented. In this research, backfire characteristics are analyzed as functions of the intake valve opening timing and compression chamber pressure under piston by using RICEM (Rapid Intake Compression Expansion Machine) that has reverse uni-flow scavenging. As the result, reverse uni-flow scavenging is advantage about back fire. but, it exists suitable intake valve opening timing and its timing become known that equivalence ratio 1 retard until the piston rises. Also, To rise chamber pressure of lower piston, this does not cause backfire occurs in equivalent ratio 0.6 observed back fire. Therefore, 2cycle hydrogen fueled free-piston engine is undesirable scavenging compression by compressing the piston.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.316-322
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• 2012

A fuel cell vehicle has the hydrogen detection sensors for checking the hydrogen leakage because it use hydrogen for its fuel and can't use a odorant to protect the fuel cell stack. To verify the hydrogen safety of leakage we select the high possible leak points of fittings in hydrogen storage system and test the leaking behavior at them. The hydrogen leakage flow rate is 10, 40, 118 NL/min and the criterion for maximum hydrogen leakage is based on allowing an equivalent release of combustion energy as permitted by gasoline vehicles in FMVSS301. There are total 18EA hydrogen leakage detection sensors installed in test system. we acquire the hydrogen leakage detection time and determine the ranking. Hydrogen leakage detection time decrease when hydrogen leakage flow rate increase. The minimum hydrogen leakage detection time is about 3 seconds when the flow rate is 118NL/min. In this study, we optimize hydrogen sensor position in fuel cell vehicle and verify the hydrogen leakage safety because there is no inflow inside the vehicle.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.227-230
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• 2006

The method of mass flow rate measurement using a critical nozzle is well established in the flow satisfying ideal gas law. However, in the case of measuring high-pressure gas flow, the current method shows invalid discharge coefficient because the flow does not follow ideal gas law. Therefore an appropriate equation of state considering real gas effects should be applied into the method. The present computational study has been performed to give an understanding of the physics of a critical nozzle flow for high-pressure hydrogen gas and find a way for the exact mass flow prediction. The two-dimensional, axisymmetric, compressible Navier-Stokes equations are computed using a fully implicit finite volume method. The real gas effects are considered in the calculation of discharge coefficient as well as in the computation. The computational results are compared with the previous experimental data and predict well the measured mass flow rates. It has been found that the discharge coefficient for high-pressure hydrogen gas can be corrected properly adopting the real gas effects.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.84-90
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• 2013

The hydrogen or oxygen gas producted by electrolysis become many bubbles in the electrolyte, but exact data on the behavior of these bubbles in the separator of an electrolysis stack didn't become known. In this study, the flow visualization experiment on the behavior of bubbles in the flow pattern of the array type separator is performed by using of a visible alkaline electrolysis stack and a stereoscopic microscope. As the results, a fine size bubbles adhered to the surface of the flow pattern grow to large sized bubbles until each bubble's buoyance is lager than the sum of external force and weight. And then the large bubbles flow into the upper area of the separator. Bubbles adhered to the surface of the vertical flow pattern grow quickly than them adhered to the surface of the horizontal flow pattern. Also, he electrolysis efficiency is declined because many multi-size bubbles occupied the wide volume in the flow pattern.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.7
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• pp.28-33
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• 2022

In this study, we analyze the flow characteristics according to the internal shape of a 700bar hydrogen charging gun for hydrogen electric vehicles. When charging hydrogen, it receives a high-pressure charging pressure. At this time, we analyze the flow characteristics according to the shape of the nozzle and find the shape of the nozzle that minimizes energy loss. Ultimately, the optimal design of the nozzle was obtained by comparing the pressure difference between the inlet pressure and outlet pressure under a fixed mass flow condition.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.5
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• pp.385-394
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• 2019

The analysis of temperature behavior of a hydrogen tank during refueling is of significance to clarify the safety of the compressed hydrogen storage in vehicles since the temperature at a tank rises with inflow of hydrogen. A mass balance and an energy balance were combined to obtain analytical model for temperature change during the hydrogen refueling. The equation was coupled to Peng-Robinson-Gasem (PRG) equation of state (EOS) for hydrogen. The PRG EOS was adopted after comparison with other four different cubic EOSs. A parameter of the model was determined to fit data from experiments of various inlet flow rates and temperatures. The temperature and pressure change with refueling time were obtained by the developed model. The calculation results revealed that the extent of precooling was more effective than the flow rate control.