• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.2
• /
• pp.1-9
• /
• 2012

Applicability of regenerative cooling in 2,500 N-class bipropellant thruster using hydrogen peroxide and kerosene was considered for improvement of performance and application in various missions. Calculation was performed by one dimensional approach using hydrogen peroxide as a coolant. The heat flux of thruster at nozzle throat was estimated at 18 - 20 MW/$m^2$. Designed cooling channel width and height were 2.5 mm and 0.5 mm, respectively. Based on designed cooling channel configuration, flat plate model was manufactured and tested for estimation of pressure drop in cooling channel, and CFD analysis was compared with the test result. The maximum error between CFD analysis and experimental result was approximately 13% and average error was approximately 5%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.163-170
• /
• 2011

Applicability of regenerative cooling in 2,500 N-class bipropellant thruster using hydrogen peroxide and kerosene was considered for improvement performance and application in various missions. Calculation was performed by one dimensional approach using hydrogen peroxide as a coolant. In designed regenerative cooling thruster, heat flux at nozzle throat was estimated at 18 ~ 20 $MW/m^2$. Designed cooling channel width and height were 2.5 mm and 0.5 mm, respectively. Based on designed cooling channel configuration, flat plate model was manufactured and tested for estimation of pressure drop in cooling channel, and CFD analysis was compared with the test result. The maximum error between CFD analysis and experimental result was approximately 13% and average error was approximately 5%.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.512-512
• /
• 2000

In this article, a current mode peak detector circuit is presented. The simple circuit configuration comprises four MOS transistors and one external capacitor. The realization method is suitable fur fabrication using CMOS technology and all transistors are operated in their saturation region. The proposed circuit exhibits a very low drop rate and provides high accuracy, high-speed and wide dynamic range. The proposed circuit has very low power dissipation and operates using a single 2.5V supply. Simulation results confirmed the characteristic of the proposed circuit are also included.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.12
• /
• pp.1784-1792
• /
• 2001

Numerical analysis on a parallel flow heat exchanger(PFHE) is performed using 2 dimensional turbulent porous modeling. This modeling can consider three-dimensional configuration of passage (flat tube with micro-channels), and the stability and accuracy of numerical results are improved. The geometrical parameters(e.g., the position of separators, inlet/outlet, and porosity of passages of a PFHE) are varied in order to examine the flow and thermal characteristics and flow distribution of the single phase multiple passages system. The flow non-uniformities along the paths of the PFHE are observed to evaluate the thermal performance of the heat exchanger. The location of inlet affects the heat transfer, and the location of outlet affects the pressure drop. The porosity with the optimum thermal performance is around 0.53.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.1020-1025
• /
• 2001

Vertical canned pumps are usually applied in the power plant to transport fluids that the available suction pressure is low at the condensate system and the circulating-water system. The top of the motor driver is 5.5m above the base and the barrel and drop column extend even further below the ground. While this size and configuration may produce an efficient pumping system, it also introduces several dynamic problems which must be considered in order to obtain a reliable operation. The main problem is that the vibrational mode of the long flexible cantilever structure above the ground exist near the operational characteristics of the condensate debris system. This system's trouble has been showed at 2,086 hp condensate water loading pumps in a nuclear power plant.

• Journal of the Korea Fashion and Costume Design Association
• /
• v.22 no.2
• /
• pp.19-28
• /
• 2020

This study investigated the annual frequency and clothing type by extracting puff sleeves designs from overseas fashion collections from S/S and F/W 2017 to S/S and F/W 2019. Specifically, it analyzed production characteristics and pattern methods by the type of puff sleeve design, and found the following: In terms of the percentage of puff sleeves by season, S/S 2019 was the highest. Since Newtro, with a 1990s sensitivity, was the mainstream trend during the S/S 2019, power puff sleeves, a signature of the Newtro style, accounted for the greatest portion of this design feature. In terms of the type of clothes with puff sleeves, 'dress' (54.3%) was the highest, followed by 'shirts/blouse' (27.5%), 'jacket/coat' (12.5%), and 'padded coat/jacket' (5.7%). Specifically, puff sleeve patterns were found mostly in the 'dress' category, more than 47% every season, while the figures were more than 23%, 9.3%, and 2.6% in 'shirts/blouse', 'jacket/coat' and 'padded coat/jacket', respectively. In other words, puff sleeve designs were more common in 'dress' or 'shirts/blouse' than in a 'padded coat/jacket'. In general, the shoulder length is reduced to prevent the shoulders from looking broader because of puffs. In contrast, recent puff-sleeve styles differ from those introduced by modern fashion designers in that they have drop shoulders with puffs attached. Furthermore, as constructive and over-exaggerated sleeve patterns appeared, puffs were applied to diverse sleeve styles including mutton leg and Mameluke styles. The analysis results of this study will contribute to the development of the fashion industry through small quantity batch production pursuing unique styles and serve as the basis for further studies on the configuration methods of puff sleeves. This study will be used in various ways, including as educational material on sleeve patterns. Through the analysis of sleeve patterns, this study tries to provide basic data for planning the design of puff sleeves and helping to diversify the ladies' apparel market in the future.

• Journal of Energy Engineering
• /
• v.24 no.4
• /
• pp.105-116
• /
• 2015

In this study, airside performance of round fin-and-tube heat exchangers are compared with that of the herringbone wave fin-and-tube heat exchangers with an aim to investigate the effect of fin shape on thermal performance. Results show that j factors of the round wave fin are 1.2~22% larger than those of herringbone wave fin. The f factors of the round wave fin are -1.0~29% smaller than those of herringbone wave fin for 1 or 2 row configuration. For 3 row configuration, f factors of the round wave fin are 8.3~23% larger. The reason may be attributed to the reduced recirculation zone in the valley of the fin for round wave fin as compared with that of the herringbone wave fin. For round wave fin, the effect of fin pitch on j and f factor is not significant. In addition, j factors decrease as the number of tube row increases. On the other hand, f factors are independent of the number of tube row. A new correlation was developed based on the present data.

• Journal of Energy Engineering
• /
• v.12 no.1
• /
• pp.35-41
• /
• 2003

Heat regenerator occupied by regenerative materials improves thermal efficiency of regenerative combustion system through the recovery of heat of exhaust gaset. By using one-dimensional two-phase fluid dynamics model, the unsteady thermal flow of heat regenerator with spherical particles, was numerically simulated to evaluate the heat transfer and pressure drop and thereby to suggest the parameter for designing heat regenerator. It takes about 7 hours for the steady state of the flow field in regenerator, in which heat absorption of regenerative particle is concurrent with the same magnitude of heat desorption. The regenerative particle experiences small temperature fluctuation below 10 K during the reversing process. The performance of thermal flow in heat regenerator varies with inlet velocity of exhaust gas and air, configuration of regenerator (cross-sectional area and length) and diameter of regenerative particle. As the gas velocity increases, the heat transfer between gas and particle enhances and with the increase the pressure losses. As particle diameter decreases, the air is preheated higher and the exhaust gases are cooled more with the increase of pressure losses.

• Korean Institute of Interior Design Journal
• /
• v.22 no.4
• /
• pp.70-77
• /
• 2013

This study has analysed the composition elements in a cafe space where visual transfer-elements are filled and the perceptual characteristics of facade designs with the purpose of drawing any important elements to advertisement and their related items for uniqueness of designs. For the analysis of the perception process shown in the consecutive situations of observing and visiting cafes, the cafe facade was grouped and stereotyped for the analysis of perceptual characteristics and significant composition elements for better designing of cafes through survey with representative facades as subjects. The conclusions from this study are the followings. First, for the uniqueness specific to cafes to be integrated into facade, memory was chosen first as the most significant advertisement factor followed by interest as with male and attention as with female. The memory has much to do with furniture and finishing material of Clause (4), Chapter 4.1 and the types having effects on perception of Clause (1) and the atmosphere having effect on that of Clause (2) were found to be major factors to attention and interest. Second, it was found out that women preferred horizontally stable partition and men clearly divided facades. The factor of shape was observed first among the constituents of facade followed by color. There was no difference with 'shape' between men and women and color was found to be a space constituent having a lot of effects on women. Third, the memory of experience from visiting a cafe was very likely to offer the motivation of visiting it again, on which furniture had the most effect followed by finishing material and color. Such elevation elements as facade and logo were found not to have effect on the memory or the re-visit. Any intention of visiting again seemed to be influenced by such comprehensive images as atmosphere rather than by any concrete facade, furniture, or appliance. From the above viewpoint, facade design should have any uniqueness or impressive feature as well as the effect of making passers-by drop in and attracting them into the shop. The analysis of attributes of facade constituents revealed that the abstract images in addition to the configuration of facade had much to do with interest or behavior.

• Transactions of the Korean hydrogen and new energy society
• /
• v.6 no.2
• /
• pp.53-63
• /
• 1995

A 100kW class stack consisting of 10 molten carbonate fuel cells has been fabricated. Internally manifold stack has been tested for endurance. Each cell in the stack had an electrode area of $100cm^2$ and reactant gases were distributed in each cells in a cross-flow configuration. Initial and long term operation performance of the stack was investgated as a function of gas utilization using a specially designed small scale stack test facility. It was possible to have a stack with an output of more than 100W using an anode gas of 72% $H_2/18%$ $CO_2/10%H_2O$ and cathode gas of 33% $O_2/67%$ $CO_2$ and 70% Air 30% $CO_2$. The output and voltage of the stack at a current 15A($150mA/cm^2$) and gas utilization of 0.4 showed 125.8W and 8.39V respectively by elapsed time of 310 hours operation. In long term operation characteristics, the voltage drop of 52.4mV/1000hour was observed after more than 1,840 hours operation. Among the voltage drop, the OCV loss was highest than other voltage loss such as internal resistance and electrode polarization. Non uniformity of 2voltages and degradation of cell voltage in the stack was observed in according to changing the utilization rate after a long term operation. Further work for increasing the performance prolonging the life of the stack are required.