• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.4
• /
• pp.12-20
• /
• 2017

The ablation characteristics of graphite nozzle throat insert was analyzed for the use in solid rocket propulsion system. The propulsion system was composed of three types of conventional nozzles, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants were used in ten kinds of propulsion system that had different shapes with each other. Total forty eight tests were performed. From the results of the analysis, it was found that the ablation rate was increased for the higher average chamber pressure and the higher oxidizer mole fraction. A useful correlation for nozzle throat ablation rate was developed in terms of the chamber pressure, oxidizer mole fraction, and throat size. The calculated ablation rates from the correlation showed agreement within ${\pm}0.10mm/s$ with the experimentally determined values.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.19 no.1
• /
• pp.59-65
• /
• 2013

In recent years, the crisis of energy is growing seriously and also the contamination of ecology has been reverberated as international problem. The social concerns on energy crisis have been growing for the last several years and also the interests in new and renewable energy have been increased. Therefore, in order to solving these problems, as solution of one, this paper is investigated using the aeration system at the fish farm, etc from nature energy such as wind power. This study suggests the fundamental data of designing for these similar apparatus and examines the parameters of wind velocity and wind receiving area. Especially, the water outlet position was mainly investigated with optimum outlet angle of wind pump.

• Proceedings of the Membrane Society of Korea Conference
• /
• 2003.11a
• /
• pp.146-148
• /
• 2003

Bayer 공정은 가성소다를 이용하여 보오크사이트로부터 수산화알루미늄을 추출하는 공정이다. 그러나 보오크사이트 추출 후 1차 침전공정에서 반응한 보오크사이트 잔사는 침전시킴으로써 깨끗한 공정액을 분리하는 데 이때 침전되지 못한 다량의 분산성 고형물이 공정액 중에 존재하게 되는데 이를 분산성 보오크사이트(레드머드) 미립자라하며 보통 80-100mg/$\ell$의 농도를 나타낸다. 그러므로 이를 제거하기 위해 다음 공정인 입상여과필터 공정을 사용하는데 이때 필터링 효율증대를 위해 보조제로써 다량의 소석회(Ca(OH)$_2$)를 투여하여 공정액 중의 고형물을 농도를 8-100mg/$\ell$에서 5mg/$\ell$로 낮추는 공정을 사용하고 있다. 특히 국내 수산화알루미능 제조회사일 KC(주)의 경우 소석회 사용량이 일 10톤, 년간 약 3,600톤을 사용함으로써 소석회의 사용량에 따라 같은 량의 슬러지가 발생되게 된다. 따라서 여과후 발생되는 슬러지의 처리비용 문제(연간 9천만원)와 소석회의 미립자에 의한 공정액의 2차 오염과 제품 품질 저하(quality claim) 및 소석회 사용량에 따른 연간 원료비(연간 3억원) 등의 상당한 문제점을 나타내고 있는 실정이다. 아울러 최근 고품위 수산화알루미늄의 공급 요구에 따라 여과시 정제기준이 점차 낮아져 이제는 1mg/$\ell$ 이하를 유지하여야 하는 근본적인 문제에 봉착해있는 실정이다. 그러므로 본 연구에서는 소석회를 사용하는 입상여과법을 대체하기 위한 신공정개발을 추진하였으며, 그동안 카트리지여과법 등의 다양한 실험 결과로부터 최근 필터 보조제를 첨가하지 않는 물리적 여과방법인 세라믹 막 여과법의 적용 가능성을 확인하고 친환경공정인 세라믹 막 여과 실용화 공정 기술을 개발하였다. 세라믹 막 여과 법은 여과 보조제를 사용하지 않으므로 2차적인 슬러지 발생등의 환경문제를 발생하지 않으며, 공정액에 첨가제를 투입하지 않으므로 순환형 친환경공정으로 각광받을 수 있다. 본 연구에서는 고온, 고농도의 NaOH 수용액의 처리에 적합한 막소재와 발생될 수 있는 제반 문제점 등을 파악하였고, 장기간의 실험을 거쳐 최적 투과 압력(Trans membrane pressue), 세정 조건 및 주기, 막재질에 있어서 보강하여야 할 Point, 최적 운전 조건들을 토출해 내었고, 향후 실제 Plant에 적용할 계획이다.

• Journal of the Semiconductor & Display Technology
• /
• v.19 no.1
• /
• pp.79-84
• /
• 2020

Unlike a printing process, it is difficult to pattern organic thin films in the longitudinal (coating) direction using a coating process. In this paper, we have investigated the feasibility of patterning organic thin films using needles. To this end, we have slot-coated an aqueous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solution in the form of a fine stripe or large area and then applied the dual needle; one for discharging the main solvent of the underlying thin film and the other for sucking the dissolved thin film. We have found that the pattern width and depth increase as the moving speed of the plate decreases. However, it is observed that the sidewall slope is very gentle (the length of the slope is of the order of 200 ㎛) due to the fact that the discharged main solvent is widely spread and then isotropic etching occurs. With this scheme, we have also demonstrated that a fine stripe can be obtained by scanning the dual needle closely. To demonstrate its applicability to solution-processable organic light-emitting diodes (OLEDs), we have also fabricated OLED with the patterned PEDOT:PSS stripe and observed the insulation property in the strong light-emitting stripe.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.25 no.2
• /
• pp.124-131
• /
• 2016

Several research works for finding and optimizing the methods of dispensing high viscosity phosphor used in the fabrication of white LED's are currently in progress. High viscosity phosphor dispensing with a high accuracy is crucial because the dispensing rate and uniformity directly affect parameters such as the CIE chromaticity diagram, color temperature and luminous flux of white LED's. This study presents a novel method of dispensing high viscosity phosphor using electrohydrodynamic printing. The dispensing rate was optimized less than 0.01 mg phosphor using experiments and optimizing the process parameters including the standoff distance from the nozzle to the substrate, ink supply pressure, and multi-step pulsed waveform magnitude ratio. The dispensing rate was measured by dispensing 20 dots using drop-on-demand with the optimized parameters, and the experiments were repeated 10 times to maximize the data accuracy. The average dispensing rate that can be reliably used for high viscosity phosphor dispensing was 0.0052 mg.

• Proceedings of the SAREK Conference
• /
• 2008.11a
• /
• pp.561-566
• /
• 2008

The reciprocating compressor is widely used in the industry field, because it has simple principle and high efficiency. In this work, in order to improve design of discharge passage line in hydrogen compression system Numerical analysis was conducted. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including velocity, pressure and turbulence kinetic energy distribution of hydrogen gas going out from the cylinder to discharge-path line are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows velocity, pressure and turbulent kinetic energy are not distributed uniformly along the passage of the Hydrogen system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement might be done.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.10
• /
• pp.883-890
• /
• 2005

In this study, 2 pure hydrocarbon refrigerants of R1270 (Propylene) and R290 (Propane) and 3 binary mixtures composed of R1270, R29O and R152a were tested in a refrigerating bench tester with a scroll compressor in an attempt to substitute R502 used in most of the low temperature applications. The test bench provided 3\sim3.5$ kW capacity and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions resulting in the average saturation temperatures of -28 and $45^{\circ}C$ in the evaporator and condenser, respectively. Test results showed that all refrigerants tested had $9.6\sim18.7\%$ higher capacity and $17.1\sim27.3\%$ higher COP than R502. The compressor discharge temperature of R1270 was similar to that of R502 while those of all other refrigerants were $23.7\sim27.9\%$ lower than that of R502. For all alternative refrigerants, the amount of charge was reduced up to $60\%$ as compared to R502. Overall, these alternative refrigerants offer better system performance and reliability than R502 and can be used as long term substitutes for R502 due to their excellent environmental properties.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.5-13
• /
• 2017

To lunch the Korea Space Launch Vehicle-II(KSLV-II), the second launch complex will be constructed on the Naro Space Center and Kerosene Filling System (KFS) will be also installed newly. KFS of KSLV-II launch complex system is being designed based on Naro Launch Complex. But this must supply fuel to fuel tanks of the vehicle with only a supply pump because KSLV-II is a 3-stage launch vehicle unlike Naro Launch Vehicle or Test Launch Vehicle (TLV). A sudden rise of pump output pressure is recognized during fuel filling scenario selection process. This occurs because return flow can not actively deal with a lot of flow change using flow control method of orifice type. To solve this problem, it is verified that fuel can be stably supplied by installation of accumulator and an appropriate adjustment of filling mode change sequence through flow analysis of various cases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.12
• /
• pp.791-798
• /
• 2011

In this study, performance of R410A(50%R32/50%R125) and HFC32/HFC125 mixture is measured to examine the effect of composition shift of R410A used for various air-conditioners and heat pumps. The composition of HFC32/HFC125 mixture varies from the reference composition of R410A ${\pm}10%$ with 5% interval. Tests carried out in a heat pump bench tester at the evaporation and condensation temperatures of $7/45^{\circ}C$ and $-7/41^{\circ}C$ for summer and winter conditions, respectively. Test results show that both the coefficient of performance (COP) and compressor power of the HFC32/HFC125 mixture have the maximum difference of 2.0% as compared to those of R410A. Compressor discharge temperatures of HFC32/HFC125 mixture are increased up to $6.7^{\circ}C$ as compared to that of R410A. The amount of charge for HFC32/HFC125 mixture vary within 5.6% as compared to that of R410A. Overall, performance of R410A is not appreciably affected by the composition shift of ${\pm}10%$ of R32 under both air-conditioning and heat pumping conditions.

• Solar Energy
• /
• v.19 no.4
• /
• pp.71-80
• /
• 1999

For developing a new measuring device which enables the thermal resistance at comers of the building envelope in addition to the plate wall measuring device, computer simulations were performed to clarify the problems produced during previous tests. For the optimum design to reduce the temperature deviation in measuring device, the specifications of the measuring devices are to be as follows : Dimension of the device is $500{\times}500{\times}100mm$ in size, heating plate is seperated to some degree from the inner surface of the measuring device, lower temperature of heating plate is as effective as possible, fans should be located at the upper part in the measuring device and face to downward.