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구준모(Junemo Koo),강용태(Yongtae Kang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Nanofluids have been studied as possible alternatives for heat transfer fluids to improve the efficiency of heat exchangers. There are deviations of measured effective thermal conductivities between research-groups, and the mechanisms of the effective thermal conductivity enhancement of nanofluids are not confirmed yet. In this study, the effects of particle shape on the effective thermal conductivity enhancement are discussed and presented as a possible explanation of the deviations. The particle motion effect is found to be negligible for nanofluids of high aspect ratio cylindrical particles, which is believed to be important for nanofluids of spherical particles, while the percolation network formation and contact resistance play dominant roles in determining the effective thermal conductivity.
구준모(Junemo Koo),정정열(Jungyeul Jung),강용태(Yongtae Kang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
A new one-dimensional simulation model to predict the surface coverage and average thickness of coating films obtained from spin coating processes is developed adopting moving mesh technique. The effects of initial profile, d ispensed volume, solvent vapor pressure, relative humidity and initial v iscosity on the coating film geometry are investigated numerically. The initially dispensed volume, solvent vapor pressure, initial viscosity and wafer rotation speed are found to be effective parameters to control the surface coverage and average film thickness. The relations between spin coating process parameters and the film geometry parameters, surface coverage and average film thickness, are derived from the new model. It is found that the photoresist solution consumption per a given size of chips could be reduced by optimizing the operation parameters.