• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.2
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• pp.131-139
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• 2000

A direct hydrogen liquefaction equipment has been developed and tested, which consists of a GM refrigerator, a liquefaction vessel, a radiation shield, a cryostat, and an ortho-para converter with catalyst. The effect of ortho-para hydrogen conversion on the performance of hydrogen liquefaction has been investigated. The time needed for the hydrogen liquefaction process with hydrogen pressure charge of 4 atm was delayed to around 75 minutes, and the liquefied mass flow rate of the hydrogen was about 0.0150∼ 0.0205 g/s when the hydrogen was liquefied with the direct hydrogen liquefaction system considering ortho-para conversion. With ortho-para conversion, the liquefied mass flow rate decreased up to 20%. Considering ortho-para conversion, there were up to 30% increase in the work input per unit liquefied mass flow rate. When the ortho-para conversion was considered, FOM decreased to be about 0.031∼0.045.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.7-11
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• 2019

We have investigated the effect of the hydrogen flow rate on the characteristics of IZO thin films for the TCO (transparent conducting oxide). For this purpose, IZO thin films are deposited by RF magnetron sputtering at 300℃ with various H₂ flow rate. To investigate the influences of the ambient gases, the flow rate of hydrogen in argon was varied from 0.1 sccm to 1 sccm. The IZO thin films deposited at 300℃ show crystalline structure having an (222) preferential orientation. The electrical resistivity of the crystalline-IZO films deposited at 300℃ and hydrogen gas of 0.8sccm was 3.192×10^-4Ω cm, the lowest value. As the hydrogen gas flow rate increased, the resistivity tended to decrease. The XPS profiles showed that the number of oxygen vacancy decreased as the hydrogen flow rate increased. The transmittance of the IZO films deposited at 300℃ were showed more than 80%.

• Journal of the Semiconductor & Display Technology
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• v.17 no.2
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• pp.6-11
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• 2018

In this study, we have studied the effect of substrate temperature and hydrogen flow rate on the characteristics of MZO thin films for the TCO(Transparent conducting oxide). MZO thin films were deposited by RF magnetron sputtering at room temperature and $100^{\circ}C$ with various $H_2$ flow rate(1sccm~4sccm). In order to investigate the effect of hydrogen gas flow rate on the MZo thin film, we experimented with changing the hydrogen in argon mixing gas flow rate from 1.0sccm to 4.0sccm. MZO thin films deposited at room temperature and $100^{\circ}C$ show crystalline structure having (002), (103) preferential orientation. The electrical resistivity of the MZO films deposited at $100^{\circ}C$ was lower than that of the MZO film deposited at room temperature. The decrease of electrical resistivity with increasing substrate temperature was interpreted in terms of the increase of the charge carrier mobility and carrier concentration which seems to be due to the oxygen vacancy generated by the reducing atmosphere in the gas. The average transmittance of the MZO films deposited at room temperature and $100^{\circ}C$ with various hydrogen gas flow was more than 80%.

• Journal of Environmental Science International
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• v.6 no.4
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• pp.399-407
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• 1997

The pyrolysis reactions of atomic hydrogen with chloroform were studied In a 4 cm 1.6. tubular flow reactor with low flow velocity 1518 cm/sec and a 2.6 cm 1.4. tubular flow reactor with high flow velocity (1227 cm/sec). The hydrogen atom concentration was measured by chemiluminescence titration with nitrogen dioxide, and the chloroform concentrations were determined using a gas chromatography. The chloroform conversion efficiency depended on both the chloroform flow rate and linear flow velocity, but 416 not depend on the flow rate of hydrogen atom. A computer model was employed to estimate a rate constant for the initial reaction of atomic hydrogen with chloroform. The model consisted of a scheme for chloroform-hydrogen atom reaction, Runge-Kutta 4th-order method for Integration of first-order differential equations describing the time dependence of the concentrations of various chemical species, and Rosenbrock method for optimization to match model and experimental results. The scheme for chloroform-hydrogen atom reaction Included 22 elementary reactions. The rate constant estimated using the data obtained from the 2.6 cm 1.4. reactor was to be 8.1 $\times$ $10^{-14}$ $cm^3$/molecule-sec and 3.8 $\times$ $10^{-15}$ cms/molecule-sec, and the deviations of computer model from experimental results were 9% and 12% , for the each reaction time of 0.028 sec and 0.072 sec, respectively.

• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.415-420
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• 2010

This study is focused on the channel design of bipolar plate in the electrode of hydrogen gas generator. The characteristics of hydrogen gas generation was studied in view of efficiency of hydrogen gas generation rate and a tendency of gas flow through the riv design of electrode. Since the flow rate and flow pattern of generated gas in the two phase flow system are the most crucial in determining the efficiency of hydrogen gas generator, we adopted the commercial analytical program of COMSOL MultiphysicsTM to calculate the theoretical flow rate of hydrogen gas from the outlet of gas generator and flow pattern of two phase fluid in the electrode. In this study, liquid electrolyte flows into the bipolar plate and decomposed into gas phase, two phase flow simulation is applied to measure the efficiency of hydrogen gas generation.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.4
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• pp.362-370
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• 2006

The purpose of this paper was to investigate the reforming characteristics and optimum operating condition of the plasmatron assisted $CH_4$ reforming reaction for the hydrogen-rich gas production. Also, in order to increase the hydrogen production and the methane conversion rate, parametric screening studies were conducted, in which there were the variations of the $CH_4$ flow ratio, $CO_2$ flow ratio, vapor flow ratio, mixing flow ratio and catalyst addition in reactor. High temperature plasma flame was generated by air and arc discharge. The air flow rate and input electric power were fixed 5.1 l/min and 6.4 kW, respectively. When the $CH_4$ flow ratio was 38.5%, the production of hydrogen was maximized and optimal methane conversion rate was 99.2%. Under these optimal conditions, the following synthesis gas concentrations were determined: $H_2$, 45.4%; CO, 6.9%; $CO_2$, 1.5%; and $C_2H_2$, 1.1%. The $H_2/CO$ ratio was 6.6, hydrogen yield was 78.8% and energy conversion rate was 63.6%.

• Journal of the Korean Applied Science and Technology
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• v.27 no.1
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• pp.61-69
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• 2010

This study is focused on the modeling of two phase fluid flow system in the electrode of hydrogen gas generator. The characteristics of hydrogen gas generation was studied in view of efficiency of hydrogen gas generation rate and a tendency of gas flow through the riv of electrode. Since the flow rate of generated gas is the most crucial in determining the efficiency of hydrogen gas generator, we adopted the commercial analytical program of COMSOL $Multiphysics^{TM}$ to calculate the theoretical flow rate of hydrogen gas from the outlet of gas generator.

• Journal of the Semiconductor & Display Technology
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• v.20 no.1
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• pp.1-6
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• 2021

We have investigated the effect of the substrate temperature and hydrogen flow rate on the characteristics of AZO thin films for the TCO (transparent conducting oxide). For this purpose, AZO thin films were deposited by RF magnetron sputtering at room temperature and 300℃ with various H2 flow rate. Experiments were carried out while varying the hydrogen gas flow rate from 0sccm to 5.0sccm in order to see how the hydrogen gas affects the AZO thin films. AZO thin films deposited at 300℃ showed amorphous structure, whereas IZO thin films deposited at room temperature showed crystalline structure having an (222) preferential orientation. The electrical resistivity of the AZO films deposited at 300℃ was 4.388×10-3Ωcm, the lowest value. As the hydrogen gas flow rate increased, the resistivity tended to decrease.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.525-533
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• 2022

In this study, in order to numerically analyze the heat flow characteristics in the valve according to the opening rate for the solenoid valve for hydrogen supply applied to the hydrogen storage tank, flow characteristics were comparatively analyzed. Through the analysis of pressure and temperature distributions within the valve according to the high-pressure supply condition of 70 MPa or more, the heat flow characteristics in the valve, inlet and outlet passage according to the opening rate of the valve were identified. As a result a sudden change in the fluid behavior appears in the neck region of the valve, and it is understood that the flow separation caused by the flow path shape of the expanded tube has a dominant influence on the flow characteristics. And, it was confirmed that the shape of the valve seat is a factor significantly affecting the improvement of flow rate and differential pressure performance.

• 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.