• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.662-669
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• 2000

Based on the viscous flow characteristics of gas through capillary tube, a simple and low cost system was developed for controlling gas concentration for use in C.A experiments. The gas flow rate through capillary tube had a linear relationship with pressure, $(length)^{-1}$ and $(radius)^4$ of capillary tube, which agreed well with Hagen-Poiseuille's law. The developed system could control the gas concentration in storage chamber within ${\pm}0.3%$ deviation compared to the preset concentration. The required time for producing target gas concentration in storage chamber was exactly predicted by the model used in this study, and it required much longer time than the calculated time which divided the volume of chamber by flow rate. Therefore, for producing target gas concentration as quickly as possible, it needs to supply higher flow rate of gas during the initial stage of experiment when gas concentration in storage chamber has not reached at target value. It appeared that the developed system was very useful for C.A experiments. Because one could decide a desired flow rate by the prediction model, control flow rate freely and easily by changing pressure in the pressure-regulating chamber and the accuracy was high.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.56-66
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• 1998

The absorption process of water vapor in a liquid film is an important process in LiBr-Water absorption system. The composition of the gas phase, in which a non-absorbable gas is combined with the absorbate, influences the transport characteristics. In the present work, the absorption processes of water vapor into aqueous solutions of lithium bromide in the presence of non-absorbable gas are investigated. The continuity, momentum, energy and diffusion equations for the solution film and gas are formulated in integral forms and solved numerically. It is found that the mass transfer resistance in gas phase increases with the concentration of non-absorbable gas. However the primary resistance to mass transfer is in the liquid phase. As the concentration of non-absorbable gas in the absorbate increases, the interfacial temperature and concentration of absorbate in solution decrease, which results in the reduction of absorption rate. The reduction of mass transfer rate is found to be significant for the addition of a small amount of non-absorbable gas to the pure vapor, especially at the outlet of tube where the non-absorbable gas accumulates. At higher non-absorbable gas concentration, the decrease of absorption rate seems to be linear to the concentration of non-absorbable gas.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.165-176
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• 2005

Natural gas in deep sediment may occur in three phases based on the physical and chemical conditions. If the concentration of gas in pore water is less than the solubility, gas is dissolved. If the concentration of gas is greater than its solubility (water is saturated or supersaturated with gas), gas occurs as a fee gas below the gas hydrate stability Lone (GHSZ) and is present as solid hydrate within the GHSZ. The knowledge of gas concentration in deep sediment appears critical to determine the phase of natural gases and to understand the formation and distribution of gas hydrate. However, reliable data on gas concentration are usually available only from the upper section of marine sediment by the headspace gas technique, which is widely used for sampling of gases from the sediments. The headspace gas technique represents only a fraction of gases present in situ because sediments release most of the gases during recovery and sampling. The PCS (Pressure Core Sampler) is a downhole tool developed to recover a nominal $1{\cal}m$ long, $4.32{\cal}cm$ diameter core containing $1,465cm^3$ of sediment, pore water and gas at in situ pressure up to 68.9 MPa. During Leg 204, the PCS was deployed at 6 Sites. In situ methane gas concentration and distribution of gas hydrate was measured by using PCS tool. Characteristics of methane concentration and distribution is different from site to site. Distribution of gas hydrate in the study area is closely related to characteristics of in situ gas concentration measured by PCS.

• Journal of the Korean Society of Safety
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• v.7 no.3
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• pp.35-42
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• 1992

Ignition energy effects of concentration of mixed gas In closed cylindrical vessel(1, 832㎤) are studied. The ignition energy ranged from 25 Joule to 110 Joule, and hidrogen and methane gases were used for flammable gas at stoichiometric condition with oxygen gas and nitrogen gas (N2) was for inert gas, which concentration was maximum 60% . The explosion pressure, temperature, concentration of product gases were calculated. It is found that - The explosion pressure and explosion velocity increase with ignition energy. - The gradience of explosion velocity with ignition energy is steeper than explosion pressure. - The results of calculation are similiar with results of experiment. - NOx is not serious product gas for methane and hydrogen gas, but CO is serious at certain concentration for methane in asphyxiation.

• Journal of Sensor Science and Technology
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• v.29 no.3
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• pp.211-214
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• 2020

Chlorine dioxide is very effective gas for sterilization or disinfection (in manufacturing), and does not produce harmful by-products after use. However, if its concentration exceeds 10 %, it become explosive and cannot be compressed or stored. Therefore, it is necessary to measure its concentration. In this study, the concentration of chlorine dioxide with a high oxidizing strength was measured using a metal oxide sensor. The sensor was a commercially available TGS series from Figaro. The sensitivity of the sensor was inversely proportional to a low concentration of chlorine dioxide gas below 6 ppm and returned to the initial resistance at about 6 ppm. When the gas concentration reached multiples of 10 ppm, resistance of the sensor increased to several megaohms.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.499-509
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• 1998

In the absorption process of water vapor in a liquid film, the composition of the gas phase, in which a non-absorbable gas is combined with the absorbate influences the transport characteristics remarkably. In the present study, the absorption processes of water vapor into aqueous solution of lithium bromide in the presence of non-absorbable gases were investigated analytically. The continuity, momentum, energy and diffusion equations for the solution film and gas phase were formulated in integral forms and solved numerically. It was found that the mass transfer resistance in gas phase increased with the concentration of non-absorbable gas. However the primary resistance to mass transfer was in the liquid phase. As the concentration of non-absorbable gas in the absorbate increased, the liquid-vapor interfacial temperature and concentration of absorbate in solution decreased, which resulted in the reduction of absorption rate. The reduction of mass transfer rate was found to be significant for the addition of a small amount of non-absorbable gas to the pure vapor, especially at the outlet of an absorber where non-absorbable gases accumulated. At higher non-absorbable gas concentration, the decrease of absorption flux was almost linear to the volumetric concentration of non-absorbable gas.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.586-589
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• 2002

The Ultra Violet(UV) emission characteristics of Neon + Nitrogen gas-mixture discharge was investigated in AC plasma display panel. The firing voltage of Ne+$N_2$ gas-mixture discharge increased with increasing nitrogen concentration. The UV intensity emitted from the gas discharge also increased with increasing nitrogen concentration. The UV efficiency increase with increasing $N_2$ partial pressure at low $N_2$ concentration, and then UV efficiency is saturated at high $N_2$ concentration.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.4
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• pp.273-280
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• 1998

The investigation on the removal of 502 gas fro.In flue gas which causes serious air pollution was made by using a semi dry flue gas desulfurization method. Experiments were carried out as a function of process variables which would affect SO2 removal efficiency. Process variables inclilded SO2 inlet concentration, inlet temperature of simulated flue gas, sorbent weight fraction, and volume flow rate of sorbent slurry. In this study, used sorbent was Ca(OH), and simulated flue gas was prepared by mixing pure SO2 gas with air. Experimental conditions were varied at 140~18$0^{\circ}C$ of inlet temperature of the simulated flue gas, 500~2000ppm of inlet SO2 concentration, 0.4~1.0% of sorbent concentration, and 10~25 mL/min of flow rate of sorbent slurry. Among process variables, inlet concentration of SO2 was found to be the most significant factor to affect SO2 removal efficiency. The concentration of Ca(OH2) had a lower effect on SO2 removal than SO2 inlet concentration removal amount was 0.108, 0.141, 0.153 g SO2/g Ca(OH)2 respectively- As 200 mmol of HNO3 was added into slurry to improve removal efficiency, initial pH was maintained and solubility of slurry increased, so that removal efficiency elevated. Adding over 200 mmol of HNO3 into slurry caused removal efficiency lower. Therefore it could be concluded the optimum was 200 mmol of HNO3 input.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.371-376
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• 2001

Radiative transfer by nongray gas mixtures with nonuniform concentration and temperature profiles were studied by using the statistical narrow-band model and ray-tracing method with the sufficiently accurate $T_{60}$ quadrature set. Transmittances through the nonhomogeneous gas mixtures were calculated by using the Curtis-Godson approximation. Three different cases with different temperature and concentration profiles were considered to obtain benchmark solutions for nongray gas mixtures with nonuniform concentration and temperature profiles. The solutions obtained from this study were verified and found to be very well matched with the previous solutions for uniform gas mixtures. The results presented in this paper can be used in developing various solution methods for radiative transfer by nongray gas mixtures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.707-711
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• 2013

Carbon nanotubes(CNT) has strength and chemical stability, greatly conductivity characteristics. In particular, MWCNT (multi-walled carbon nanotubes) show rapidly resistance sensitive for changes in the ambient gas, and therefore they are ideal materials to gas sensor. So, we fabricated NOx gas sensors structured MOS-FET using MWCNT (multi-walled carbon nanotubes) material. We investigate the change resistance of NOx gas sensors based on MOS-FET with ultra lean NOx gas concentrations absorption. And NOx gas sensors show sensitivity on the change of gate-source voltage ($V_{gs}=0[V]$ or $V_{gs}=3.5[V]$). The gas sensors show the increase of sensitivity with increasing the temperature (largest value at $40^{\circ}C$). On the other hand, the sensitivity of sensors decreased with increasing of NOx gas concentration. In addition, We obtained the adsorption energy($U_a$), $U_a$ = 0.06714[eV] at the NOx gas concentration of 8[ppm], $U_a$ = 0.06769[eV] at 16[ppm], $U_a$ = 0.06847[eV] at 24[ppm] and $U_a$ = 0.06842[eV] at 32[ppm], of NOx gas molecules concentration on the MWCNT gas sensors surface with using the Arrhenius plots. As a result, the saturation phenomena is occurred by NOx gas injection of concentration for 32[ppm].