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Jongwook Choi Sungcho Kim Jeong Soo Kim 《Journal of Mechanical Science and Technology》2006,20(7):1089-1097
The market demand of display devices is drastically increasing in the information technology age. The research on OLED (Organic
Light Emitting Diodes) display with the luminescence in itself is being more paid attention than LCD (Liquid Crystal display)
with the light source from the back. The vapor deposition process is most essential in manufacturing OLED display. The temperature
distribution of the linear cell in this process is closely related to securing the uniformity of organic materials on the
substrate. This work analyzed the temperature distribution depending on the intervals between the crucible and the heating
band as well as on the amount of the heat flux from the heating band. Moreover, the roles of the water jacket and the configuration
of the cover within the linear cell were examined through the temperature analysis for six configurations of the linear cell.
Under the above temperature analysis, the variations in the intervals and the amount of the heat flux were considered to have
an effect on building the uniform temperature distribution within the crucible. It is predicted that the water jacket and
the adequate configuration of the cover will prevent the blowout and clogging phenomena, respectively. The results can be
used as the fundamental data for designing the optimal linear cell. 相似文献
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Jongwook Choi Kim Sungcho Kim Jeongsoo 《Journal of Mechanical Science and Technology》2005,19(6):1329-1337
The OLED (Organic Light Emitting Diodes) display recently used for the information indicating device has many advantages over
the LCD (Liquid Crystal Display), and its demand will be increased highly. The linear cell should be designed carefully considering
the uniformity of thin film on the substrate. Its design needs to compute the temperature field analytically because the uniformity
for the thin film thickness depends on the temperature distribution of the source (organic material). In the present study,
the design of the linear cell will be modified or improved on the basis of the temperature profiles obtained for the simplified
linear cell. The temperature distributions are numerically calculated through the STAR-CD program, and the grids are generated
by means of the ICEM CFD program. As the results of the simplified linear cell, the temperature deviation was shown in the
parabolic form among the both ends and the center of the source. In order to reduce the temperature deviation, the configuration
of the rectangular ends of the crucible was modified to the circular type. In consequence, the uniform temperature is maintained
in the range of about 90 percent length of the source. It is expected that the present methods and results on the temperature
analysis can be very useful to manufacture the vapor deposition device. 相似文献
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Sungcho Kim Jeong Soo Kim Jongwook Choi Jeong Park Soon Duk Kwon 《Journal of Mechanical Science and Technology》2008,22(6):1174-1180
The compressible flow field is numerically analyzed in a two-dimensional converging-diverging nozzle of which the area ratio,
exit to throat, is 1.8. The solver is FLUENT and the embedded RNG k − ε model is adopted to simulate turbulent flow. The plume characteristics such as shock-cell structure are discussed when nozzle
pressure ratio and stagnation temperature at the nozzle entrance are varied. The downstream flow field can be classified into
two types based on the shock shapes generated near the nozzle exit. First, a reiterative pattern in the plume is not formed
between the slip streams in case that a strong lambda-type shock wave exists. Second, when oblique shock waves are crossing
each other on the nozzle centerline, a shock cell structure appears in the plume field. Even when the flow field is changed
due to stagnation temperature, the upstream of the shock wave is little affected. Especially, the pressure distributions on
the nozzle centerline behind the shock wave are rarely influenced by the stagnation temperature, that is, the product of density
and temperature is nearly constant provided that the working fluid is a perfect gas. Therefore, the pressure field shows quasi-isobaric
behavior far downstream. 相似文献
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Jeong Park Oh Boong Kwon Jin Han Yun Sang In Keel Han Chang Cho Sungcho Kim 《International Journal of Hydrogen Energy》2008
Numerical study is conducted to clarify preferential diffusion effects of H2 and H on flame characteristics in synthetic diffusion flames of the compositions of 80% H2/20% CO and 20% H2/80% CO as representatively H2-enriched and CO-enriched H2/CO flames. Impacts of CO2 addition to the flames are also examined through the variation of added CO2 mole fraction from 0 to 0.5. A comparison was made by employing a mixture-averaged diffusivity and the suppression of the diffusivities of H and H2. It is found that preferential diffusion effects on maximum flame temperature cannot be explained by the well-known behavior between maximum flame temperature and scalar dissipation rate but by chemical processes. The concrete evidence is also presented through the examination of the behavior of maximum H mole fraction and the behavior of importantly-contributing reaction steps to overall heat release rate. 相似文献
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Choi Jongwook Kim Sungcho Jung Hun 《Journal of Mechanical Science and Technology》2004,18(9):1680-1688
The information indicating device plays an important part in the information times. Recently, the classical CRT (Cathod Ray
Tube) display is getting transferred to the LCD (Liquid Crystal Display) one which is a kind of the FPDs (Flat Panel Displays).
The OLED (Organic Light Emitting Diodes) display of the FPDs has many advantages for the low power consumption, the luminescence
in itself, the light weight, the thin thickness, the wide view angle, the fast response and so on as compared with the LCD
one. The OLED has lately attracted considerable attention as the next generation device for the information indicators. And
also it has already been applied for the outside panel of a mobile phone, and its demand will be gradually increased in the
various fields. It is manufactured by the vapor deposition method in the vacuum state, and the uniformity of thin film on
the substrate depends on the temperature distribution in the point-cell source. This paper describes the basic concepts that
are obtained to design the point-cell source using the computational temperature analysis. The grids are generated using the
module of AUTOHEXA in the ICEM CFD program and the temperature distributions are numerically obtained using the STAR-CD program.
The temperature profiles are calculated for four cases, i.e., the charge rate for the source in the crucible, the ratio of
diameter to height of the crucible, the ratio of interval to height of the heating bands, and the geometry modification for
the basic crucible. As a result, the blowout phenomenon can be shown when the charge rate for the source increases. The temperature
variation in the radial direction is decreased as the ratio of diameter to height is decreased and it is suggested that the
thin film thickness can be uniformed. In case of using one heating band, the blowout can be shown as the higher temperature
distribution in the center part of the source, and the clogging can appear in the top end of the crucible in the lower temperature.
The phenomena of both the blowout and the clogging in the modified crucible with the nozzle-diffuser can be prevented because
the temperature in the upper part of the crucible is higher than that of other parts and the temperature variation in the
radial direction becomes small. 相似文献
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