Numerical study on flow and heat transfer behavior of vortex and film composite cooling

Li Liang,Du Changhe,Chen Xiuxiu,Wang Jiefeng,Fan Xiaojun 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.6

The complete vortex and film composite cooling model is established to study the flow and heat transfer behavior. Influences of coolant Reynolds number, film hole diameter and inject angle on vortex and film composite cooling property are thoroughly discussed. Results show that the vortex nozzle coolant mass flux increases along the vortex chamber axial direction, while the film hole coolant mass flux and blowing ratio decrease along the vortex chamber axial direction. The internal heat transfer intensity will increase along the vortex chamber axial direction. The adiabatic film cooling efficiency decreases downstream due to counter rotating vortex pairs (CRVP) lift off wall effects. The coolant rotational velocity in vortex chamber increases with the increasing Reynolds number, thus leading to obvious heat transfer enhancement. An increase in Reynolds number results in an increase in CVRP intensity, hence the adiabatic film cooling efficiency will turn lower. The coolant rotational velocity and internal heat transfer intensity will decrease with the increase of film hole diameter. The CRVP intensity and film hole jet coolant mass flux increases with the increasing film hole diameter, leading to an increase in adiabatic film cooling efficiency. The rotational coolant flow and heat transfer intensity are not sensitive to inject angle. As the inject angle increases, the CRVP intensity changes little and the inject coolant owns larger inclined angle with gas mainstream flow, therefore the adiabatic film cooling efficiency will increase.

Life cycle emissions of greenhouse gas for ammonia scrubbing technology

Shujuan Wang,Fang Liu,Changhe Chen,Xuchang Xu 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.3

is thought that the CO2 emissions from coal-fired power plants contribute greatly to the total anthropo-genic CO2 emissions. Ammonia solvent can be used to absorb the CO2, caled amonia scrubbing. However, as hasbeen pointed out, the production of ammonia would emit CO2; therefore, the efectiveness of amonia scrubbing isdoubted. The paper focuses on the problem. Two systems are defined in the paper. System I is CO2 absorption by am-2 emissions of the twosystems are calculated by means of life cycle asessment. The paper shows that the total CO2 emissions of ammoniascrubbing are less than that of the industrial production of fertilizer ammonium bicarbonate. It can be concluded thatammonia scrubbing is an effective way to reduce the anthropogenic CO2 emissions.

Catalytic reduction of nitric oxide by methane over CaO catalyst

Wei Xu,Huiling Tong,Changhe Chen,Xuchang Xu 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.1

The selective catalytic reduction of nitric oxide by methane was studied over CaO catalyst in a bubbling fluidized bed in the temperature range of 800-900 oC, in which NO cannot be reduced by CH4 without CaO catalyst. The nitric oxide conversion was found to depend on oxygen and CH4 feed concentration, and also on temperature. In addition, the presence of water vapors in the flue gas enhanced the NO reduction admirably well in the absence of O2. But water vapor has an inhibiting effect on the reaction while O2 is present in the flue gas. The addition of CO2 poisoned the CaO catalyst and exhibited a detrimental effect on NO conversion at the working temperature range, 800-900 oC. However, with a temperature rise to 900 oC the CO2 poisoning effect on NO reduction was weakened. The mechanism was studied and discussed according to the references in the paper.

Cutting fluid corrosion inhibitors from inorganic to organic: Progress and applications

Haogang Li,Yanbin Zhang,Changhe Li,Zongming Zhou,Xiaolin Nie,Yun Chen,Huajun Cao,Bo Liu,Naiqing Zhang,Zafar Said,Sujan Debnath,Muhammad Jamil,Hafiz Muhammad Ali,Shubham Sharma 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.5

Water-based cutting fluid has a broad application area and a hundred year history, but its poor corrosioninhibition and anti-rust ability limit its further promotion. Adding corrosion inhibitors can effectively solve the aboveproblems. However, no review papers are available on cutting fluid corrosion inhibitors, and their mechanism, suitability,and performance influencing factors have not been revealed. This article discusses cutting fluid corrosion inhibitorsto fill the gaps in theoretical research and industrial applications. Inorganic matters are initially used in corrosion inhibitiondue to their strong oxidizing properties. Therefore, the film formation mechanism of inorganic corrosion inhibitoroxide and precipitation film is first analyzed, and the applications in corrosive medium are summarized. Given thatinorganic corrosion inhibitors are not environmentally friendly and expensive, organic corrosion inhibitors are currentlyused as replacement. Thus, the film formation mechanism of different organic corrosion inhibitors adsorptionfilm is analyzed, and their suitability with metals is determined. The influence of molecular structure and temperatureon their corrosion inhibition effect is also studied, and the performance of inorganic and organic corrosion inhibitors iscompared. However, single organic corrosion inhibitors are greatly affected by metal surface state, temperature, andimmersion time. Therefore, the synergistic film formation after the compounding of organic and inorganic corrosioninhibitors is analyzed. In addition, the influence rate of concentration, molecular structure, and temperature on corrosioninhibition performance is revealed, and a matching database of corrosion inhibitor type and metal type in cuttingis established. Finally, in view of the limitations of cutting fluid corrosion inhibitors, the establishment of a moleculardynamics model of corrosion inhibitor failure and accelerates corrosion and the development of general-purpose greenadditives based on the molecular design and physical and chemical analysis of the suitability of corrosion inhibitor andbase liquid are prospected.

Effects of water vapor, CO_2 and SO_2 on the NO reduction by NH_3 over sulfated CaO

Xinfang Yang,Bo Zhao,Yuqun Zhuo,Changhe Chen,Xuchang Xu 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.8

Gas effects on NO reduction by NH_3 over sulfated CaO have been investigated in the presence of O_2 at 700-850℃ . CO_2 and SO_2 have reversible negative effects on the catalytic activity of sulfated CaO. Although H_2O alone has no obvious effect, it can depress the negative effects of CO_2 and SO_2. In the flue gas with CO_2, SO_2 and H_2O coexisting,the sulfated CaO still catalyzed the NO reduction by NH_3. The in situ DRTFTS of H2O adsorption over sulfated CaO indicated that H_2O generated Brønsted acid sites at high temperature, suggesting that CO_2 and SO_2 competed for only the molecularly adsorbed NH_3 over Lewis acid sites with NO, without influencing the ammonia ions adsorbed over Brønsted acid sites. Lewis acid sites shifting to Brønsted acid sites by H_2O adsorption at high temperature may explain the depression of the negative effect on NO reduction by CO_2 and SO_2.

Influences of A- or B-site substitution on the activity of LaMnO3 perovskite-type catalyst in oxidation of diesel particle

Bailei He,Qiang Song,Qiang Yao,Zhongwei Meng,Changhe Chen 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.3

was partially substituted at A- or B-site by Sol-Gel method and characterized by XRD, SEMand BET. Perovskite oxides were formed in all substitutions. The catalytic activities of substituted catalysts on carbonblack oxidation were measured by Temperature Programing Oxidation (TPO). Experimental results showed that allsubstitutions increased the catalytic activity of LaMnO3, and La0.8Cs0.2MnO3 showed the highest catalytic activity. Undertight contact, the activity enhancement of diferent substitutions decreased in the order Cs>K>V>Ce>Co>Cu>Fe.Dynamic analysis showed that partial substitutions increased the pre-exponential factor and the catalytic activity byincreasing the oxygen vacancy on the catalyst surface. The active components on the surfaces of La0.8Ce0.2MnO3 andLaMn0.8V0.2O3 included CeO2 and LaVO4, which changed the apparent activities and dynamic parameters of these twocatalysts.

Mass transfer and kinetics study on the sulfite forced oxidation with manganese ion catalyst

Zhao Bo,Li Yan,Zhuo Yuqun,Tong Huiling,Zhang Xiaowen,Chen Changhe 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.3

limestone scrubbing is the most common flue gas desulfurization process (FGD) for control of sulfurdioxide emissions from the combustion of fossil fuels. Forced oxidation, which controls the overall reaction of the sulfurdioxide absorption, is the key path of the process. Manganese which comes from the coal is one of the catalysts duringthe forced oxidation process. In the present work, the two-film theory was used to analyze the sulfite forced oxidationreaction with an image boundary recognition technique, and the oxidation rate was experimentally studied by contactingpure oxygen with a sodium sulfite solution. There was a critical sulfite concentration 0.328 mol/Lwithout catalyst ortion constant k; furthermore, we obtained the order with respect to the sulfite and Mn2+ concentrations. When the Mn2+catalyst concentration was kept unchanged, the sulfite oxidation reaction rate was controlled by dual film and the reac-tion kinetics was first order with respect to sulfite while concentration was below 0.328 mol/L; the sulfite oxidationreaction rate was controlled by gas film only and the reaction kinetics was zero order with respect to sulfite while concentration over 0.328 mol/L. When concentration was kept unchanged, the sulfite oxidation reaction rate de-pended on gas-liquid mass transfer and the reaction kinetics was diferent in various stages with respect to Mn2+ con-centrations.

Nanoscale Etching of La0.7Sr0.3MnO3 without Etch Lag using Chlorine Based Inductively Coupled Plasma

Nimphy Sarkar,Jaewoo Han,Daryll Joseph Chavez Dalayoan,Satyabrat Behera,Sang-Hyuk Lee,Cheng Chen,Dai-Sik Kim,Changhee Sohn,남궁선 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.4

La0.7Sr0.3MnO3 (LSMO) has been considered as a promising material for future electronic and spintronic device applicationdue to its unique properties such as pure spin polarization, colossal magnetoresistance, and high temperature coefficient ofresistance (TCR). To apply this promising material for practical application, large epitaxial LSMO layers should be etchedinto micro- and nano-scale device structures. However, a comprehensive study on the etch of LSMO has not been demonstratedyet. Herein, the etch rates of LSMO are studied using inductively coupled plasma reactive ion etching (ICP-RIE)method, while controlling critical etching parameters such as ICP source power, radio frequency (rf) chuck power, etchinggas ratio, and chamber pressure. We found that the etching process can be applied to nanoscale structures (down to 100 nm)without etch lag effect, exhibiting smaller etch depth in smaller features. This study will provide a good reference for theetching and the engineering of LSMO toward future electronic and spintronic devices such as highly sensitive bolometersand low-power memory devices.