• Title/Summary/Keyword: Carbon flow

Search Result 1,399, Processing Time 0.033 seconds

Effect of Gas Phase Cycling Modulation of C2H2/SF6 Flows on the Formation of Carbon Coils (탄소 코일 생성에 대한 C2H2/SF6 기체유량의 싸이클릭 변조 효과)

  • Lee, Seok-Hee;Kim, Sung-Hoon
    • Journal of the Korean Vacuum Society
    • /
    • v.21 no.3
    • /
    • pp.178-184
    • /
    • 2012
  • Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils were investigated as functions of additive gas flow rate and the cycling on/off modulation of $C_2H_2/SF_6$ flows. Even in the lowest $SF_6$ flow rate (5 sccm) in this work, the cycling on/off modulation injection of $SF_6$ flow for 2 minutes could give rise to the formation of nanosized carbon coils, whereas the continuous injection of $SF_6$ flow for 5 minutes could not give rise to the carbon coils formation. With increasing $SF_6$ flow rates from 5 to 30 sccm, the cycling on/off modulation injection of $SF_6$ flow confines the geometry for the carbon coils to the nanosized ones. Fluorine's role of $SF_6$ during the reaction was regarded as the main cause for the confinement of carbon coils geometries to the nano-sized ones.

Experimental Study on the Secondary Flow Characteristics of a Supercritical Carbon Dioxide Flow in a Gas Cooling Process Within a Square Duct (정사각 덕트 초임계 상태 이산화탄소 가스 냉각과정 중 2차 유동 특성 측정 연구)

  • Han, Seong-Ho;Seo, Jung-Sik;Kim, Young-Chan;Kim, Min-Soo;Choi, Young-Don
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.32 no.2
    • /
    • pp.158-165
    • /
    • 2008
  • The carbon dioxide properties change sharply near the critical or pseudo-critical point in the heat transfer processes. The reduction in turbulent, convective heat transfer parameters observed in some supercritical data and in experiments with common gases can be due to property variation, acceleration, buoyancy or combinations of these phenomena, depending on the conditions of the applications. In this study, the measurement for the secondary flow driven by buoyancy was carried out on the supercritical carbon dioxide turbulent flows in the different boundary condition with the constant mass flow rate. The available measuring techniques were used to clarify the behaviour of any supercritical fluid. Laser Doppler Velocimeter (LDV) and a special device was used to measure the secondary velocity and turbulent characteristics of the supercritical flows.

Combustion Characteristics of Methane/Oxygen in Pre-Mixed Swirl Flame (메탄/순산소 예혼합 화염의 선회특성)

  • Kim, Han-Seok;Choi, Won-Seok;Cho, Ju-Hyeong;Ahn, Kook-Young
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.33 no.5
    • /
    • pp.343-348
    • /
    • 2009
  • The present study has experimentally investigated the effects of $CO_2$ diluted oxygen on the structure of swirl-stabilized flame in a lab-scale combustor. The methane fuel and oxidant mixture gas ($CO_2$ and $O_2$) were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame characteristics were examined for various amount of carbon dioxide addition to the methane fuel and various swirl strengths. The effects of carbon dioxide addition and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using chemiluminescence techniques to provide information about flow field. The results show that the hot combustion zone increases at the upstream reaction zone because of an increase in the recirculation flow for an increase in swirl intensity. The hot combustion zone is also increased at the downstream zone by recirculation flow because of an increase in swirl intensity which results in higher centrifugal force. The OH and CH radical intensities of reaction zone decrease with carbon dioxide addition because the carbon dioxide plays a role of diluted gas in the reaction zone.

Fluid flow dynamics in deformed carbon nanotubes with unaffected cross section

  • Rezaee, Mohammad;Yeganegi, Arian;Namvarpour, Mohammad;Ghassemi, Hojat
    • Advances in nano research
    • /
    • v.12 no.3
    • /
    • pp.253-261
    • /
    • 2022
  • Numerical modelling of an integrated Carbon NanoTube (CNT) membrane is only achievable if probable deformations and realistic alterations from a perfect CNT membrane are taken into account. Considering the possible forms of CNTs, bending is one of the most probable deformations in these high aspect ratio nanostructures. Hence, investigation of effect associated with bent CNTs are of great interest. In the present study, molecular dynamics simulation is utilized to investigate fluid flow dynamics in deformed CNT membranes, specifically when the tube cross section is not affected. Bending in armchair (5,5) CNT was simulated using Tersoff potential, prior to flow rate investigation. Also, to study effect of inclined entry of the CNT to the membrane wall, argon flow through generated inclined CNT membranes is examined. The results show significant variation in both cases, which can be interpreted as counter-intuitive, since the cross section of the CNT was not deformed in either case. The distribution of fluid-fluid and fluid-wall interaction potential is investigated to explain the anomalous behavior of the flow rate versus bending angle.

Filter- and Denuder-Based Organic Carbon Correction for Positive Sampling Artifacts

  • Hwang, InJo;Na, Kwangsam
    • Asian Journal of Atmospheric Environment
    • /
    • v.11 no.2
    • /
    • pp.107-113
    • /
    • 2017
  • This study describes (1) the impact of positive sampling artifacts caused by not only a filter-based sampling, but also a denuder-based sampling in the determination of particle-phase organic carbon (POC), (2) the effect of sample flow rate on positive artifacts, and (3) an optimum flow rate that provides a minimized negative sampling artifact for the denuder-based sampling method. To achieve the goals of this study, four different sampling media combinations were employed: (1) Quartz filter-alone (Q-alone), (2) quartz filter behind quartz-fiber filter (QBQ), (3) quartz filter and quartz filter behind Teflon filter (Q-QBT), and (4) quartz filter behind carbon-based denuder (Denuder-Q). The measurement of ambient POC was carried out in an urban area. In addition, to determine gas-phase OC (GOC) removal efficiency of the denuder, a Teflon filter and a quartz filter were deployed upstream and downstream of the denuder, respectively with varying sample flow rates: 5, 10, 20, and 30 LPM. It was found that Q-alone sampling configuration showed a higher POC than QBQ, Q-QBT, and Denuder-Q by 12%, 28%, and 23%, respectively at a sample flow rate of 20 LPM due to no correction for positive artifact caused by adsorption of GOC onto the filter. A lower quantity of GOC was collected from the backup quartz filter on QBQ than that from Q-QBT. This was because GOC was not in equilibrium with that adsorbed on the front quartz filter of QBQ during the sampling period. It is observed that the loss of particle number and mass across the denuder increases with decreasing sample flow rate. The contribution o f positive arti facts to POC decreased with increasing sample flow rate, showing 29%, 25%, and 22% for 10, 20, and 30 LPM, respectively. The 20 LPM turns out to be the optimum sample flow rate for both filter and denuder-based POC sampling.

Catalytic effects of heteroatom-rich carbon-based freestanding paper with high active-surface area for vanadium redox flow batteries

  • Lee, Min Eui;Kwak, Hyo Won;Jin, Hyoung-Joon
    • Carbon letters
    • /
    • v.28
    • /
    • pp.105-110
    • /
    • 2018
  • Owing to their scalability, flexible operation, and long cycle life, vanadium redox flow batteries (VRFBs) have gained immense attention over the past few years. However, the VRFBs suffer from significant polarization, which decreases their cell efficiency. The activation polarization occurring during vanadium redox reactions greatly affects the overall performance of VRFBs. Therefore, it is imperative to develop electrodes with numerous catalytic sites and a long cycle life. In this study, we synthesized heteroatom-rich carbon-based freestanding papers (H-CFPs) by a facile dispersion and filtration process. The H-CFPs exhibited high specific surface area (${\sim}820m^2g^{-1}$) along with a number of redox-active heteroatoms (such as oxygen and nitrogen) and showed high catalytic activity for vanadium redox reactions. The H-CFP electrodes showed excellent electrochemical performance. They showed low anodic and cathodic peak potential separation (${\Delta}E_p$) values of ~120 mV (positive electrolyte) and ~124 mV (negative electrolyte) in cyclic voltammetry conducted at a scan rate of $5mV\;s^{-1}$. Hence, the H-CFP-based VRFBs showed significantly reduced polarization.

Removal Characteristic of Nitrogenous Compounds According to the Combination of Feeding Ratio between the Supernatant of Precipitation Tank and Raw Domestic Wastewater (침전조 상등액과 유입하수의 유량대비에 따른 하수 내 질소 화합물 제거특성)

  • Park, Sang Min;Park, Jin Hee
    • Journal of the Korea Organic Resources Recycling Association
    • /
    • v.13 no.4
    • /
    • pp.128-135
    • /
    • 2005
  • This study was done to improve the effectiveness of nitrification and denitrification using the aeration-anoxic combination method using CFSTR(continuous-flow stirred-tank reactor) attached with an anoxic reactor filled with a media. In order to calculate the concentration of nitric acid within the aeration tank proportional to the anoxic rate within the reactor, supernatant within the inflow and precipitation tanks were influxed into the anoxic reactor. The rate of nitrogen removal was calculated using the concentration of inflow and flow of returned supernatant. From the results of this experiment, the carbon source needed in the anoxic reactor came from the inflow so that anoxification was achieved completely using the inflow source without the introduction of an external carbon source. However, as the ratio of nitric acid becomes large in inflow and nitric acid flow, the carbon source within the input source decreases so that the concentration of carbon source is important.

  • PDF

Study on the Relationship between Aggregation Structure and Flow Rate Depending on Extrusion Temperature at Complex Mold of (Activated Carbon/Polymer Binder) ((활성탄/고분자바인더)복합성형체의 압출온도에 따르는 응집구조 및 유량 상관성에 관한 연구)

  • Lim, Yong Gyun;Kim, Young Jun;Park, Sang Jin;Hong, Sung-Kyu
    • Korean Chemical Engineering Research
    • /
    • v.52 no.2
    • /
    • pp.261-265
    • /
    • 2014
  • As the need for miniaturization in water purification filter increases, the development of filter media for single filtration with multiple function was strongly required. In this study, the molded activated carbon composed of single unit was manufactured by extrusion-sintering process, and then the flow rate, density and porosity were investigated using the molded activated carbon manufactured at various extrusion temperature. We confirmed that it was possible to manufacture the single unit-molded activated carbon when the extrusion temperature was $140{\sim}230^{\circ}C$ more than $133^{\circ}C$ being of polymer binder melting point, and the optimal extrusion temperature for the molded activated carbon with maximum flow rate was $170^{\circ}C$ since the molded activated carbon had low density and high through porosity. Also we confirmed that the flow rate through the molded activated carbon was strongly dependent upon through pore porosity compared to total porosity for the molded activated carbon.

Growth of Carbon Nanotubes using Plasma-Enhanced Chemical Vapor Deposition (플라즈마 CVD 를 이용한 탄소나노튜브의 성장)

  • Bang Y.Y.;Chang W.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2005.06a
    • /
    • pp.1236-1239
    • /
    • 2005
  • Aligned carbon nanotubes(CNTs) array were synthesized using DC plasma-enhanced chemical vapor deposition. Silicon substrate Ni-coated of 5nm thickness were pretreated by $NH_3$ gas with a flow rate of 180sccm, for 10min. CNTs were grown on the pretreated substrates at $30%\;C_2H_2:NH_3$ flow ratios for 10min. Carbon nanotubes with diameters from 60 to 80 nanometers and lengths about 2.7 micrometers were obtained. Vertical alignment of carbon nanotubes were observed by FESEM.

  • PDF

A Study on the Oxidation of Carbon Monoxide for Exhaust of Car Engine by the $LaSrNiCoO_3$ Low Noble Metal Catalyst (저귀금속 $LaSrNiCoO_3$ 촉매에 의한 자동차 배기중의 일산화탄소의 산화반응에 관한 연구)

  • 이근배;이석희
    • Journal of Korean Society for Atmospheric Environment
    • /
    • v.6 no.1
    • /
    • pp.57-72
    • /
    • 1990
  • The oxidation of carbon monoxide on a catalyst, $LaSrNiCoO_3$ was investigatigated with a plug flow system. Kinetic quantities such as reaction-rate, reaction order and Arhenius-parameters at various reactor temperature from 200$^\circ$C to 300$^\circ$C were determined. Also, the optimum condition for the oxidation of carbon monoxide with this catalyst was determined and are as follows. Partial pressure of oxigen ; 428mmHg Partial pressure of carbon monoxide ; 332mmHg Mixed moral ratio of oxigen and Carbon monoxide ; 1.3 : 1 Total gas flow ; 224ml/min Reaction temperature ; 340$^\circ$C The reaction kinetic equation at the optimum condition, temperature range from 200$^\circ$C to 340$^\circ$C, are as follow. $$ $v = Ae^{6.5Kcal/RT} [CO]^{0.93 \sim 0.98} [O_2]^{0.42 \sim 0.50}$ $$ In addition to this, numerical calculation were performed to evaluate the mass and heat transfer effect on this system.

  • PDF