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내부 온도분포를 고려한 Coal-Water Slurry의 점화현상에 관한 이론적 해석
최창은,백승욱,김종욱,Choi, C.E.,Baek, S.W.,Kim, J.W. 대한기계학회 1993 대한기계학회논문집 Vol.17 No.7
CWS(coal-water slurry) is used for application in power plants, boilers, industrial furnaces. A single coal-water slurry droplet ignition has been examined to reveal the basic nature of their evaporation, volatilization and heating processes. The interior droplet temperature distribution has been considered. The effect of coal thermal conductivity, droplet size, water fraction in the slurry, gas temperature and velocity and radiation on the ignition phenomena were also studied. Either increasing the velocity and gas temperature or decreasing the droplet size and water fraction in the slurry may reduce the time for evaporation and ignition delay time.
최창은,박재현,박승욱,Choe, Chang-Eun,Park, Jae-Hyeon,Park, Seung-Uk 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.10
Single liquid droplet combustion processes including heating, evaporation, droplet burning and flame radiation were theoretically investigated by adopting nongray gas radiation model for the radiative transfer equation (RTE). n-Heptane was chosen as a fuel and the numerical results were compared with the experimental data available in the literature. The discrete ordinate method (DOM) was employed to solve the radiative transfer equation and the weighted sum of gray gases model (WSGGM) was applied to account for nongray effect by CO$_{2}$, and H$_{2}$0. Therefore, detailed effects by nongray gas and its comparison with the gray gas model could be figured out in the results. It is found that the radiative heat flux is higher when the nongray model is used, thereby reducing the maximum gas temperature and the flame thickness, but the total burning time increases due to the deceased conductive heat flux in nongray model. Consequently, a better agreement with experimental data could be obtained by using nongray model.
최창의 대한교통학회 1987 大韓交通學會誌 Vol.5 No.2
The methods of the transportation plan evaluation have appearently been improved. Yet we are frequently confronted with many problems when we are trying to apply those various methods in practice. This paper aims at reviewing the major problems in the transportation plan evaluation and considering the way to resolve such kinds of problem. The selection of the evaluation criteria and the weighting systems between such criteria are the moat important things in the multi-criteria approaches. In this respect, this paper suggests some alternative evaluation criteria in consideration of the levels and the purpose of the plan. Also the increased capacities and new demands of generated trip are the main effects of the transportation investment. Nevertheless such significant effects have been neglected in the calculation of benefits due to the transportation investment in the past. Therefore this paper suggests that the surplus capacities and new demands of generated trip according to the alternative investment plans should be included in the calculation of benefits for the plan evaluation.