• 한국결정성장학회지
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• 제19권4호
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• pp.208-213
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• 2009

석탄 화력발전소에서 발생되는 바닥재와 준설토를 이용하여 인공경량골재를 제조하였다. 소성 옹도별, 골재 조 성별, 그리고 석회석($CaCO_3$)을 코팅 양별 비교를 통하여 골재 표면에 형성된 융제량의 변화, 비중, 흡수율, 절단면 관찰 등의 골재 물성 비교가 수행되었다. 결론적으로 골재 무게비 $CaCO_3$ 10%를 골재 표면에 코팅하여 표면개질을 암으로써 골재 내부의 거대 기공의 형성을 억제시켜 비중을 조절할 수 있었으며, 표면 융제를 대폭 감소시켜 골재간 융착 현상을 방지할수 있으며, 흡수율 또한 효과적으로 감소시켜 경량골재를 포함한 경량콘크리트 타설시 펌핑 문제를 향상시킬 수 있을 것으로 판단되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2309-2314
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• 2007

The application analysis of bubble pump on the domestic solar water heater system is presented. The system investigated in this study is a passive device, self pumping and self regulating. It was test to use the bubble pump on solar water heater system. The test experiment has been taken on the existed vacuum tube about the efficiency, working fluid temperature and pressure and circulated power. In order to check the working temperature and working pressure effectively, the bubble pump was test separated from the solar water heater. The equipment consists of the bubble pump, heater and heat exchanger. The main structure of bubble pump was design depend on the character of two phase flow. The complete system was instrumented to measure pressures, temperatures and flow-rates at various locations. The theory analysis of design bubble pump has been given and the experiment design has been included in the paper.

• 전기학회논문지
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• 제59권9호
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• pp.1632-1637
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• 2010

A micro-water-nozzle, as one of a cooling means of micro-electronic devices, has been proposed and investigated. The I-V characteristics of the micro-water-nozzle and effect of applied voltage on the meniscus formation and deformation and ejection processes of de-ionized water on the micro-water-nozzle tip have been investigated. The water ejection processes, such as a drop formation, a drop deformation, a dripping, a cone jet, and an atomization, were taken place on the micro-water-nozzle tip by the electrohydrodynamic forces acted by the DC and AC high voltages applied on the meniscus of the micro-water-nozzle tip. The I-V characteristics of the micro-water-nozzle-to-plate electrode system were different from that of the same metal-point electrode system, due to the meniscus formation and water droplet ejection at the nozzle tip. The positive and negative DC and AC high voltages showed the water droplets ejection, the ejection rates of 1.8, 1.5 and 1.2 g/h respectively, which, however, showed that the proposed micro-water-nozzle-to-plate electrode system could be used as one of an effective pumping means.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.128-135
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• 2008

EGR(exhaust gas recirculation) is considered as a most effective method to reduce the NOx emissions. But high EGR tolerance is always pursued not only for its advantages of the pumping loss reduction and fuel economy benefit in Gasoline-Hybrid engine. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR on fuel efficiency, combustion stability, engine performance and exhaust emissions. With optimal EGR rates, the fuel consumption was improved by 4%. This improvement was achieved while a reduction in NOx emissions of 75% was accomplished. Increase of EGR gas temperature causes the charge air temperature to affect the knock phenomenon and moreover, the EGR valve lift changes for the same control signal.

• 한국자동차공학회논문집
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• 제16권4호
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• pp.143-150
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• 2008

EGR(exhaust gas recirculation) is an attractive means of improving the fuel economy of spark ignition engines, as it offers the benefits of charge dilution (lower pumping and cooling losses) while allowing stoichiometric fuelling to be retained for applications using the three-way catalysts. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate in Gasoline-Hybrid engine should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR on fuel economy, combustion stability, engine performance and exhaust emissions. EGR tolerance with load variation was found to be more sensitive than with rpm variation. With optimal EGR rates, the fuel consumption was improved by 5.5% while a combustion stability was guaranteed.

• 설비공학논문집
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• 제13권3호
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• pp.194-199
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• 2001

The turbulent flow resistance of water solution with polymer is reduced as compared with that of pure water. This effects is named th drag reduction and offers the significant reduction of the pumping power and the energy consumption. But the intense shear forces and the high temperature experienced by the polymer solution when passing through the pipes cause the degradation a loss of drag reduction effectiveness. Especially, the degradation behavior is found to be strongly dependent on temperature. This mechanical and thermal degradation can be avoided by adding materials such as surfactant to the polymer solution, which enhance the bonding force between molecules. In the present study, Copolymer and SDS were utilized and they were mixed in 10 different mixture ratios, while total concentration was fixed as 100wppm. Degradation of Copolymer-SDS mixture solutions was investigated experimentally in closed loop at the temperature of $10^{\circ}C\; and\; 80^{\circ}C$ with various flow average velocities of 1.5 m/sec, 3.0m/sec, and 4.5m/sec. Degradation characteristics of polymer solution without surfactant show a radical loss of drag reduction effectiveness at high temperature. Degradation alleviation ability of surfactant is especially effective at high temperature. Consequently, this results show that the addition of surfactant to the polymer solution can control unfavorable degradation phenomena for high temperature systems.

• 천문학논총
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• 제20권1호
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• pp.7-10
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• 2005

We have calculated 2448 interstellar cloud models to investigate the formation and destruction of high rotational level $H_2$ according to the combinations of five physical conditions: the input UV intensity, the $H_2$ column density, cloud temperature, total density, and the $H_2$ formation rate efficiency. The models include the populations of all the accessible states of $H_2$ with the rotational quantum number J < 16 as a function of depth through the model clouds, and assume that the abundance of $H_2$ is in a steady state governed primarily by the rate of formation on the grain surfaces and the rates of destruction by spontaneous fluorescent dissociation following absorption in the Lyman and Werner band systems. The high rotational levels J = 4 and J = 5 are both populated by direct formation into these levels of newly created molecules, and by pumping from J = 0 and J = 1, respectively The model results show that the high rotational level ratio N(4)/N(0) is proportional to the incident UV intensity, and is inversely proportional to the $H_2$ molecular fraction, as predicted in theory.

• 조명전기설비학회논문지
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• 제29권11호
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• pp.53-58
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• 2015

Systemic heating and cooling air conditioning systems are popular in various industrial fields and even home. Recently, the rate of supply of this kind of multi-heat pump has been increased under ESCO financing supporting system. Generally the heat pumping system has a structural simplicity and easy installation benefits. and has good running efficiency under normal designed condition. But under extreme climate condition (over $+30^{\circ}C$, under $-10^{\circ}C$), this system exposes abnormal power consumption. It causes high progressive electric power rates and resultant peak power capacity of power plant. In this paper, a novel system concept of buffering refrigerant accumulator and constant pressure control system to relieve peak power load is proposed and this system's utility is verified with an prototype experimental system.

• 한국농공학회논문집
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• 제61권4호
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• pp.55-61
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• 2019

Motor pumps cannot be used in those areas where electricity is not accessible such as remote rural areas in many African countries. Hydraulic ram pump is one of the solutions for supplying water for irrigation or domestic uses. The hydraulic ram pumps are working based on the water hammer effect for pumping without external power or electricity. This study was conducted to investigate the effect of air chamber volume and operation parameters on the performance of the hydraulic ram pump which was assembled with common plumbing parts. The experimental results showed the volume of the air chamber did not affect the performance such as discharge rate and head. When drive heights were 1.7 and 2.35 m, the maximum discharge heads were up to 7 m and 10 m, respectively. When the air chamber volume was 1 L, discharge rates were 0.23 and 2.12 L/min under the drive heights of 1.7 and 2.35 m, respectively. The average energy efficiency of the hydraulic ram pump assembled in this study was about 60% for all the experimental conditions.

• Advances in concrete construction
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• 제11권3호
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• pp.231-238
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• 2021

The present work aims at investigating the effects of using various fine mineral additions as partial replacement to Portland cement on the tribological properties of concrete. To achieve this goal, concrete mixtures were prepared with different percentages (10, 20 and 30%) of limestone fillers (LF) and natural pozzolana (NP), and (20, 40 and 60%) of blast furnace slag (BFS). The interface yield stress (τ0) and viscous constants (η) that allow characterizing friction at the concrete-pipe wall interface were determined using a rotational tribometer. In addition, the compositions of the boundary layers that formed in the pumping pipes of the different concretes under study were also identified and analyzed. The experimental results obtained showed that the concretes studied have a linear tribological behavior that can be described by the Bingham model. Furthermore, the use of different mineral additions, especially limestone fillers and blast furnace slags, even at high rates, had a beneficial effect on the optimization of the volume of paste present in the boundary layer, which made it possible to significantly reduce the viscous constant of concrete. However, a maximum rate of 10% of natural pozzolana was recommended to achieve tribological properties that are favorable to the pumpability of concrete.