• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.522-522
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• 1996

An investigation of the effects of transverse magnetic field and Peltier effect on melt convection and macrosegregation in vertical Bridgman crystal grosth of Te doped InSb was been carried out by means of microstructure observation, Hall measurement, electrical resistivity measurement and X-ray analysis. Before the experiments, Interface stability, convective instability and suppression of convection by magnetic field were calculated theoretically. After doping 1018, 1019 cm-3 Te in InSb, the temperature of Bridgman furnace was set up at $650^{\circ}C$. The samples were grown in I.D. 11mm, 100mm high quartz tube. The velocity of growth was about 2${\mu}{\textrm}{m}$/sec. In order to obtain the suppression of convection by magnetic field in the middle of growth, 2-4KG magnetic field was set on the melt. For searching of the shape of solid-liquid interface and the actual velocity of crystal growth, let 2A current flow from solid to liquid for 1second every 50seconds repeatedly (Peltier effect). The grown InSb was polycrystal, and each grain was very sharp. There was no much difference between the sample with and without magnetic field at a point of view of microstructure. For the sample with Peltier effect, the Peltier marks(striation) were observed regularly as expected. Through these marks, it was found that the solid-liquid interface was flat and the actual growth velocity was about 1-2${\mu}{\textrm}{m}$/sec. On the ground of theoretical calculation, there is thermosolutal convection in the Te doped InSb melt without magnetic field in this growth condition. and if there is more than 1KG magnetic field, the convection is suppressed. Through this experiments, the effective distribution coefficients, koff, were 0.35 in the case of no magnetic field, and 0.45 when the magnetic field is 2KG, 0.7 at 4KG. It was found that the more magnetic field was applied, the more convection was suppressed. But there was some difference between the theoretical calculation and the experiment, the cause of the difference was thought due to the use of some approximated values in theoretical calculation. In addition to these results, the sample with Peltier effect showed unexpected result about the Te distribution in InSb. It looked like no convection and no macrosegregation. It was thought that the unexpected behavior was due to Peltier mark. that is, when the strong current flew the growing sample, the mark was formed by catching Te. As a result of the phenomena, the more Te containing thin layer was made. The layer ruled the Hall measurement. The values of resistivity and mobility of these samples were just a little than those of other reference. It was thought that the reason of this result was that these samples were due to polycrystal, that is, grain boundaries had an influence on this result.

• Journal of ILASS-Korea
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• v.12 no.1
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• pp.58-64
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• 2007

The spray characteristics of the oxidizer-rich preburner are investigated. This system is generally operated at an oxidizerfuel mixture ratio of 50. The spray quality and mixing performance are very important for safe combustion. To know the spray characteristics of the oxidizer-rich preburner, we have designed various swirl injectors and measured droplet velocity and size by the PDPA system. The flow discharge coefficient of the fuel orifice is $0.12{\sim}0.21$, oxidizer orifice discharge coefficient is $0.16{\sim}0.28$. From the spray visualization, fuel nozzle spray angle is $15^{\circ}{\sim}25^{\circ}$, oxidizer nozzle spray angle is $65^{\circ}{\sim}85^{\circ}$ and combined spray angle is reduced $2^{\circ}{\sim}5^{\circ}$ compared to the oxidizer nozzle only case. From the PDPA measurement, droplet SMD is $175\;{\mu}m$ at 50 mm and $190\;{\mu}m$ at 100 mm of variant 1 combined case. The number concentration measurement revealed the reason of the droplet diameter increasement with distance. That is due to drop coalescence results from collision of drops which is occurred in dense sprays at a long distance from nozzle orifice exit.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.33-39
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• 2005

Experiments are performed to study the mixed convection flow and heat transfer in an inclined parallel plates with the upper part cooled and the lower part heated uniformly. The Reynolds number ranges from $4.0{\times}10^{-3}\;to\;6.2{\times}10^{-2}$, the angle of inclination, ${\theta}$, from 0 to 45 degree from the horizontal line, and Pr of the high viscosity fluid is 909. In this paper, the PIV(Particle image velocimetry) with TLC(Thermo-sensitive liquid crystal) tracers is used for visualizing and analysis. This method allows simultaneous measurement of velocity and temperature field at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. This paper describes the methods, and presents the quantitative visualization of mixed convection. From this study, it is found that the flow pattern can be classified into three patterns which are affected by Reynolds number and the angle of inclination.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.63-75
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• 1996

The purpose of this study is to investigate the break-up characteristics by taking advantage of a two-phase coaxial nozzle. Air and water are utilized as working fluids and the mass ratio air/water has been controlled to characterize the atomization, diffusion and development of mixing process. By way of a photographic technique, conventional developing structures and diffusion angles have been analyzed systematically with variations of mass ratios. The turbulent flow components of the atomized particles were measured by a two channel LDV system and the data were treated by an on-lined measurement equipment. According to the photographic results the spreading angles decreased because the axial inertia moment was relatively higher than the lateral one with respect to the increase of mass ratio. It is found the jet flow diffuses linearly in a certain limit region while the atomizing characteristics, in terms of the distributions of particle diameters did not show particular differences. It may be expected that these fundamental results can be used as reference data in studying the atomization, breakup and diffusions.

• Journal of ILASS-Korea
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• v.1 no.3
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• pp.51-59
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• 1996

An experiment was carried out on the structure of twin spray from pressurize-swirl nozzles, in order to investigate the effect of different size of spray nozzles on the characteristics of the overlap of two single sprays, for example, mean diameter, number density, and spatial distribution of flow rate. Using image processing method, the distributions of size and velocity of droplets of a single spray and twin spray were measured and compared to investigate the overlapping effect of two identical sprays. Comparing experimental results from a twin-spray with those from two-single sprays shows that the flow rate distribution of the twin-spray was concentrated around the midst of the overlapping region of two sprays. In this region, Sauter mean diameter (SMD) did not change much in the twin spray from 6032 nozzles, but it was smaller by 10 micrometers in the twin-spray than two-single sprays from 60063 nozzles. In spite of large difference in Weber numbers of the colliding sprays between the 60063 and 6032 nozzles, the phenomena did not have a big change in the overlapping region of twin spray. This shows that in the collision between droplets from two single spray in the overlapping region to cause the disruption of droplets, the size distribution of spray droplets was also important as well as Weber number.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.698-706
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• 2006

Experiment and numerical calculation have been peformed to investigate mixed convection heat transfer between inclined parallel plates. Particle image velocimetry (PIV) with thermo-sensitive liquid crystal (TLC) tracers is used for visualizing and analysis. This method allows simultaneous measurement of velocity and temperature fields at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. The governing equations are discretized using the finite volume method. The results are presented for the Reynolds number ranges from 0.004 to 0.062, the angle of inclination, ${\Theta}$, from 0 to 45 degree and Prandtl number of the high viscosity fluid is 909. The results show velocity, temperature and mean Nusselt numbers distributions. It is found that the periodic flow of mixed convection between inclined parallel plates is shown at $0^{\circ}{\leq}{\Theta}<30^{\circ}$, Re<0.062, and the flow pattern can be classified into three patterns which depend on Reynolds number and the angle of inclination. The minimum Nusselt numbers occur at Re=0.05 regardless of the angle of inclination.

• Journal of Power System Engineering
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• v.14 no.3
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• pp.5-12
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• 2010

The purpose of this study is to analyze heterogeneous distribution of branch-like structure at downstream region of inner spray. The previous many studies about diesel spray structure have yet stayed in the analysis of 2-D structure, and there are very few of informations which are concerned with 3-D analysis of the structure. The heterogeneous distribution of droplets in inner spray affects the mixture formation of diesel spray, and also the combustion characteristics of the diesel engines. Therefore, in order to investigate 3-D structure of evaporative spray the laser beam of 2-D plane was used in this study. Liquid fuel was injected from a single-hole nozzle (l/d=5) into a constant-volume vessel under high pressure and temperature in order to visualize the spray phenomena. The incident laser beam was offset on the central axis. From the images analysis taken by offset of laser beam, we examine formation mechanism of heterogeneous distribution by vortex flow at the downstream of the diesel spray. As the experimental results, the branch-like structure formed heterogeneous distribution of the droplets consists of high concentration of vapor phase in the periphery of droplets and spray tip of branch-like structure. Also the 3-D spatial structure of the evaporative diesel spray can be verified by images obtained from 2-D measurement methods.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.591-596
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• 2005

The objectives in the present study are to investigate that the enhancement heat transfer was experimentally measured and was compared with the acoustic pressure obtained by numerical analysis. From the results of the present study, a strong Fluid motion initiated by ultrasonic vibrations can affect heat and mass transfer. This phenomenon. called acoustic streaming, clearly observed by PIV measurement leads to increase in velocity of a Fluid which is a crucial physical concept to explain the enhancement heat transfer. The heat transfer coefficient is increased with increase in the ultrasonic intensities. The largest enhancement heat transfer (about 26%) is measured at the ultrasonic intensity of 300W. Acoustic streaming results from sudden acoustic pressure variations in the liquid. The results of numerical analysis reveal that acoustic pressure is increased by 59.5% at the ultrasonic intensity of 300W. The higher acoustic pressure near four ultrasonic transducers develops more intensive flow destroying the flow instability. Also, the profiles of acoustic pressure variation are consistent with those of enhancement heat transfer.

• Analytical Science and Technology
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• v.28 no.6
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• pp.460-466
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• 2015

An isotope dilution liquid chromatography tandem mass spectrometry was developed as a primary method for the quantitative analysis of cholesterol in infant formula. Cholesterol-d₄ was used as an internal standard and spiked into the infant formula sample. In order to release cholesterol out of cholesteryl ester, which is cholesterol bound to fatty acids in infant formula, saponification was carried out. Saponification conditions were optimized with heating temperature, reaction time and the concentration of KOH. The optimum conditions were as follows; heating temperature was 70 ℃, reaction time was 180 min and the concentration of KOH was 0.8 mL of 8 M KOH for about 0.1 g infant formula sample. Extraction of cholesterol out of sample solution was carried out with hexane uisng liquid-liquid extraction. Chromatographic analysis was carried out using Phenomenex Kinetex C₁₈ column. Mobile phase was 0.1% acetic acid in methanol/water (v/v, 99/1) and flow rate was 0.3 mL/min. Cholesterol and cholesterol-d₄ were monitored at mass transfer m/z 369/259 and 373/263 respectively. Reproducibility of the method was evaluated to be 0.23% of the measurement result. The expanded uncertainty of the measurement result of cholesterol in infant formula was approximately 1.9% at a 95% confidence level. NIST standard reference material having certified values of cholesterol in infant formula, was analyzed in order to verify this method. The ID-LC/MS/MS results were well agreed with the certified values of NIST SRM within the uncertainty.

• Journal of ILASS-Korea
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• v.6 no.3
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• pp.1-7
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• 2001

In this study, quantitative measurement of nitric oxide concentration distributions visualization were investigated in the laminar $CH_4/O_2N_2$ nixed flame by Planar laser-induced fluorescence(PLIF). The NO A-X (0,0) vibrational band around 226nm was excited using a XeCl excimer-pumped dye laser. Selecting an appropriate NO transition minimizes interference from Rayleigh scattering and $O_2$ fluorescence. The measurements were taken in $CH_4/O_2N_2$ premixed flame with equivalence ratios varying from $1.0{\sim}1.6$, and a fixed flow rate of 3slpm. NO was found to produce primarily between an inner premixed and an outer nonpremixed flame front, and total NO concentration is raised when equivalence ratios increase. These results suggest that prompt NO is likely to contribute to MO formation in $CH_4/O_2N_2$ premixed flame. Furthermore, this trend was well matched with previous works.