Air blower has been widely used in many industrial fields such as wind tunnel and large ventilation systems. Its performance is affected by operating conditions and system geometry of inpeller and duct, and these design parameter optimization is essential for the effective development. CFD analysis is carried out to investigate the air flow field characteristics with outlet total pressure in a blower system. Intake air into the impeller blade through the inlet is compressed, and then gradually discharged from the outlet with ascending total pressure, and predicted results are compared with test data. Especially this overall pressure difference in the blower system severely depends on the flow rate. These results are expected to be used as applicable design data for blower performance improvement.

PURPOSES : This study is to initiated to estimate the impact of mixed traffic flow on expressway section according to the market penetration rate(MPR) of automated vehicles(AVs) using a enhanced intelligent driver model(EIDM). METHODS : To this end, microscopic traffic simulation and EIDM were used to implement mixed traffic flow on basic expressway section and simulation network was calibrated to understand the change of impact in mixed traffic flow due to the MPR of AVs. Additionally, MOEs of mobility aspects such as average speed and travel time were extracted and analyzed. RESULTS : The result of the impact of mobility MOEs by MPR and level of service indicated that 100% MPR of AVs normally affect positive impact on expressway at all level of service. However, it was analyzed that improvements in the level of service from LOS A to C are minimal until the MPR of AVs reaches 75% or higher. CONCLUSIONS : This research shows that impact of MPR of AVs using EIDM of mixed traffic flow on basic expressway. Increasing MPR of AVs affects positive impact on expressway at all level of services. However, MPR from 25% to 75% of AVs in LOS A to C shows minimal impacts. Therefore, to maximize the effectiveness of AVs, appropriate traffic operation and management strategies are necessary.

Gate valves are hydraulic components used to shut-off the water flow in water distribution systems. Gate valves may fail owing to various aspects such as leakage through seats, wearing of packing, and corrosion. Because it is considerably challenging to detect valve malfunctioning until the operator identifies a significant fault, failure of the gate valve may lead to a severe accident event associated with water distribution systems. In this study, we proposed a methodology to diagnose the faults of gate valves. To measure the pressure difference across a gate valve, two pressure transducers were installed before and after the gate valve in a pilot-scaled water distribution system. The obtained time-series pressure difference data were analyzed using a machine learning algorithm to diagnose faults. The validation of whether the flow rate of the pipeline can be predicted based on the pressure difference between the upstream and downstream sides of the valve was also performed.

In this study, the cooling performance change according to the arrangement of the fin-tube heat exchanger using a single tube and the cooling performance change according to the air flow rate were studied. The arrangement of basic heat exchanger was set to 4 columns and 4 rows, and the performance change was studied while changing the columns and rows. In addition, the performance change was investigated by changing the air flow rate of the basic heat exchanger.

지중관수에 의한 밭작물의 농업용수는 30%이상 절감되고 가용용수량도 지표면 관수에 비해 2배 이상의 효과가 있는 것으로 알려져 있다. 이것은 수분을 지중에 공급하므로 증발산으로 인한 손실을 줄일 뿐만 아니라 지중의 확산 체적을 넓혀 지표면에 비해 수분공급 효과를 높일 수 있기 때문이다. 뿐만 아니라 관수 노동력도 절감되므로 최근 지중관수 장치의 보급이 확산되고 있는 추세이다. 그러나 우리나라는 아직까지 지중관수 장치가 개발되지 않아 농민들은 수입품 자재에 의존하고 있는 실정이다. 지중관수 장치는 3가지 중요한 기능을 가지고 있다. 첫 번째는 공급압력 100-400 kPa 사이에 유량 오차가 5-10% 범위에서 균등해야 하고, 두 번째는 토양속에서 수분을 공급하므로 뿌리가 토출구 속으로 들어가 내부의 관수구가 막히지 않아야 한다. 세 번째는 용수 공급을 중단했을 때, 관수구에서 누수가 되지 않도록 설계⋅제작되어야 한다. 또한 지중에 수분을 공급하므로 지표면 관수와 달리 이상 유무에 대해 확인하기 어려운 점이 있기 때문에 장치의 신뢰성이 높아야 한다. 따라서 지중관수 장치의 핵심은 3가지 기능을 가진 드리퍼의 개발이 우선되어야 가능하다. 유량의 균등성을 유지하는 것은 드리퍼 내부에 압력보상 기술(pressure compensation technology)에 의해 좌우된다. 드리퍼는 outer, lower insert 및 upper insert의 구성요소로 이루어져 있고, 내부에 압력조정 기능 즉, 밸브의 역할을 하는 실리콘이 내장되어 있다. 드리퍼가 유량 균등성, 뿌리 막힘 및 역류방지 기능을 수행하기 위해서 약 10가지의 설계변수를 고려해야 한다. 특히 드리퍼에서 유량이 가장 먼저 통과하는 outer의 원추 높이와 실리콘 경도는 유량 균등성에 미치는 영향이 가장 클 뿐만 아니라 공급유량의 중지 시에는 역류방지의 기능도 동시에 하게 된다. 본 연구에서 개발된 지중관수용 드리퍼의 유량 균등성은 95%를 목표로 하였다. 또한 국내서 개발한 4종의 개발품과 2종의 해외 제품을 대상으로 뿌리 침투 장면도 확인하였고, 역류 방지기능에 대해서는 관수중단점 압력 29 kPa에서 관수가 중단되는 것으로 나타나 성능이 우수한 것으로 판단되었다.

구조물 환기성능 평가에서 기존 사용된 환기 지표 (ACH: Air Change per Hour)는 유체가 거동하는 구조물 내 유량의 흡·배기량과 전체 볼륨에 의해 결정된다. 이는 구조물 내 유체 유동 중 국부적으로 정체된 흐름을 평가하는 지표로 사용하기 부적합하다. 본 논문에서는 구조물에서 국부적으로 정체된 흐름을 정량적으로 나타내기 위해 역류량을 이용하여 새로운 지표 (κ: 역류량 지수)를 제안 하고, 구조형상 변수에 의해 국부적으로 정체된 유체 흐름을 평가한다. 유체 흐름 영향인자로 구조형상 변수는 공극비 (ρ), 공극 개수 (N)로 선정한다. 전산 유체 역학 (CFD)에 의한 해석 결과, 구조형상 변수에 의한 자연 환기 성능은 유사하지만, 공극의 유무에 의한 국부 정체 기류의 크기에는 차이가 발생함이 나타난다. 또한, 역류량 지수는 구조형상 변수 각각 감소함에 따라 값이 증가하는 경향이 나타난다. 본 결과를 바탕으로 회귀분석을 통해 공극비과 공극 개수 변수에 의한 역류량과 역류량 지수의 근사값이 제시된다.

Direct water quenching technique can be used in hot stamping process to obtain higher cooling rate compared to that of the normal die cooling method. In the direct water quenching process, setting proper water flow rate in consideration of material thickness and the size of the area directly cooled in the component is important to ensure uniform microstructure and mechanical properties. In this study, to derive proper water flow rate conditions that can achieve uniform microstructure and mechanical properties, microstructure and hardness distribution in various water flow rate conditions are measured for 3.2 mm thick boron steel sheet. Hardness distribution is uniform under the flow condition of 1.5 L/min or higher. However, due to the lower cooling rate in that area, the lower flow conditions result in a drastic decrease in hardness in some areas in the hot-stamped part, resulting in low martensite fraction. From these results, it is found that the selection of proper water flow rate is an important factor in hot stamping with direct water quenching process to ensure uniform mechanical properties.

The effect of the change in air inflow velocity has been investigated at the opening of the malodor emission source to determine its influence on the Complex odor concentration. Both the Complex odor collection efficiency and concentrations were measured according to the change in airflow velocity. When the air inflow velocity was 0.1 m/s, it was observed that some of the generated gas streams were diffused to the outside due to low collection efficiency. In contrast, only the increased gas collection volume up to 0.5 m/s showed no substantial reduction of the Complex odor concentration, which indicates an increase in the size of the local exhaust system as well as the operation cost for the Complex odor control device. When the air inflow velocity reached 0.3 m/s, the Complex odor concentrations not only were the lowest, but the odorous gas could also be collected efficiently. The air inflow velocity at the opening of the malodor emission source was considered the key factor in determining the gas collection volume. Therefore, based on the results of this study, an optimal air inflow velocity might be suggestive to be 0.3 m/s.

The change in pressure measurement according to the low pressure tap blockage rate of the Venturi flowmeter used in domestic nuclear power plants was approached numerically. Blockage rates were modeled dividing by 1/10dT to the downstream side of the low pressure tab to identify differential pressure changes. As a result, differential pressure increased in proportion to the blockage rate, and there was no change in differential pressure measurement at 10 to 40 percent with relatively small blockage rate, but the error rate of 50% to 0.3% or higher was shown.

정삼투 공정(forward osmosis, FO)은 역삼투 공정(reverse osmosis, RO)에 비해 저압으로 운영되므로 오염 제어, 유지 보수, 막 세정 및 잠재적 에너지 저감 측면에서 큰 이점이 있어 다양한 분야에 적용할 수 있는 기술이다. 특히, 정삼투 공정의 막오염층이 비교적 느슨하고 분산된 특성을 가지므로 역삼투 공정과 달리 물리세정만으로도 충분한 막오염 제어가 가능하다. 하지만 기존 연구들의 경우 정삼투 물리세정에 적합한 세정 유속을 적용하지 않아 최적화 운전을 하지 못했다는 한계가 있다. 따라서 이 연구는 경제적인 에너지량으로 높은 효율의 세정을 보일 수 있는 적절한 유속의 정당성 평가를 목적으로 한다. 정삼투 공정 막오염 실험을 8.54 cm/s 순환 유속으로 유지하고 세 가지 세정유속으로 회복률과 SEC(specific energy consumption) 비교 평가하였다. 이 실험의 결과로 2배속 세정이 3배속 세정의 수투과도 회복률 만큼의 높은 효율을 보 이는 동시에, 2배속 세정이 높은 세정효율 및 경제적인 SEC를 보이는 적절한 유속이라는 것을 확인하였다.

Vortex tubes are simple tubes that can separate hot and cold air from compressed air without any internal device configuration and are used in many industries. If the vortex tube with these advantages is applied to an air conditioning system, it will be free from the use of refrigerant. In this study, basic study on discharge flow rate and temperature separation characteristics was carried out by varying the number of generator nozzle hole in various shapes of the vortex tube according to the inlet pressure of the vortex tube. Experimental results show that as the number of nozzles increases, the discharge flow rate tends to decrease and the temperature separation characteristics were excellent in the number of nozzles 6~7.

Two climate change scenarios, the RCP (Representative Concentration Pathways) 4.5 and the RCP 8.5 in the fifth Assessment Report (AR5) by Intergovernmental Panel on Climate Change (IPCC), were applied in the Yocheon basin area using the SWAT (Soil and Water Assessment Tool) model to estimate changes in flow rates and pollutant loadings in the future. Field stream flow rate data in Songdong station and water quality data in Yocheon-1 station between 2013~2015 were used for model calibration. While R2 value of flow rate calibration was 0.85 and R2 value of water qualities were in the 0.12~0.43 range. The total study period was divided into 4 sub periods as 2030s (2016~2040), 2050s (2041~2070) and 2080s (2071~2100). The predicted results of flow rates and water quality concentrations were compared with results in calibrated periods, 2015s (2013~2015). In both RCP scenarios, flow rate and TSS (Total Suspended Solid) loadings were estimated to be in increasing trend while TN (Total Nitrogen) and TP (Total Phosphorus) loadings showed decreasing patterns. Also, flow rates and pollutant loadings showed larger differences between the maximum and the minimum values in RCP 4.5 than RCP 8.5 scenarios indicating more severe effect of drought and flood, respectively. Dependent on simulation period and rainfall periods in a year, flow rate, TSS, TN and TP showed different trends in each scenario. This emphasizes importance of considerations on time and space when analyzing climate change impacts of each variable under various scenarios.

Recently, application areas based on M2M (Machine-to-Machine communications) and IoT (Internet of Things) technologies are expanding rapidly. Accordingly, water flow and water quality management improvements are being pursued by applying this technology to water and sewage facilities. Especially, water management will collect and store accurate data based on various ICT technologies, and then will expand its service range to remote meter-reading service using smart metering system. For this, the error in flow rate data transmitting should be minimized to obtain credibility on related additional service system such as real time water flow rate analysis and billing. In this study, we have identified the structural problems in transmitting process and protocol to minimize errors in flow rate data transmission and its handling process which is essential to water supply pipeline management. The result confirmed that data acquisition via communication system is better than via analogue current values and pulse, and for communication method case, applying the industrial standard protocol is better for minimizing errors during data acquisition versus applying user assigned method.

단동 이중비닐하우스에서 수막에 의한 열전달 특성 및 가온효과를 구명하기 위하여 작물이 재배되는 수막온실의 실내외 기온과 수막의 수온 등을 계측하였고, 단위 피복면적당 수막에 의한 총 공급열량, 열관류율, 관류열량, 온실 내부로 전달되는 열량비율 변화를 비교·분석하였다. 1중과 2중사이의 기온은 외부기온보다는 수막유량과 공급수온에 따라 결정되는 것으로 나타났다. 수막유량이 증가할수록, 공급수온이 높을수록 수막과 2중 하우스 내부와의 열관류율(UW-IN)은 유의하게 증가하는 경향을 보였다. 그러나 수막유량과 공급수온이 일정조건(수 막유량 0.00266L·m-2·s-1, 공급수온 19.8oC) 이상에서는 UW-IN 값이 10W·m-2·oC-1 정도로 수렴되는 것으로 나타났다. 수막과 1·2중 공기 사이의 열관류율(UW-B)의 경우에도 수막유량 및 공급수온에 따라 증가하는 경향을 보였으나, 경향성은 상대적으로 작은 것으로 분석되었다. UW-B는 연구자에 따라 전체적으로 큰 차이를 보이고 있으며, 본 연구에서는 3.27~4.44W·m-2·oC-1의 범위를 보였다. 수막에 의한 총 공급열량(QW)과 온실 내외부로 전달 되는 관류열량(QW-IN, QW-B)의 경우, QW 값이 QW-IN과 QW-B의 합과 매우 유사하게 일치하고 있어 본 연구에서 제시한 결과가 신뢰성이 있음을 확인할 수 있었다. 수막에 의해 내부공기를 가열하는데 사용되는 열량은 최대 57% 수준으로 분석되었고, 우리나라 수막재배온실의 경우 약 22~28% 수준으로 판단된다. 본 연구는 농업인이 실제 사용하는 수막온실과 가장 유사한 조건에서 수막에 의한 온도변화, 열관류율과 관류열량을 계량화함으로써 향후 경제적인 수막온실 설계 시 활용할 수 있을 것으로 기대된다.

In order to guarantee reliability of the environmental testing on defense systems, it is important to use test equipment that meets requirements of the related test standards. Especially with regard to the rain test method in MIL-STD-810G w/change 1, the latest standard, it has been highly needed to introduce a novel technique and system to provide droplet-size and precipitation-rate conditions. In this study, droplet-diameter spectra of various nozzles were measured by a high-speed camera. Then, a pair of nozzles were selected based on the experimental results showing the spectra lie within the range from 0.5 mm to 4.5 mm, as suggested in the rain test method. Also, the flow-precipitation rate calibration system was developed to precisely correlate the precipitation rate measured in the chamber and the flow rate into the nozzle bank. In conclusion, the rain test equipment has been successfully developed fulfilling the requirements of the test standard.

High-quality colloidal CdSe/ZnS (core/shell) is synthesized using a continuous microreactor. The particle size of the synthesized quantum dots (QDs) is a function of the precursor flow rate; as the precursor flow rate increases, the size of the QDs decreases and the band gap energy increases. The photoluminescence properties are found to depend strongly on the flow rate of the CdSe precursor owing to the change in the core size. In addition, a gradual shift in the maximum luminescent wave (λmax) to shorter wavelengths (blue shift) is found owing to the decrease in the QD size in accordance with the quantum confinement effect. The ZnS shell decreases the surface defect concentration of CdSe. It also lowers the thermal energy dissipation by increasing the concentration of recombination. Thus, a relatively high emission and quantum yield occur because of an increase in the optical energy emitted at equal concentration. In addition, the maximum quantum yield is derived for process conditions of 0.35 ml/min and is related to the optimum thickness of the shell material.

가상의 심지층 처분 부지에서 이루어진 지하수 유동 모의 결과를 이용하여 처분 심도의 지하수 유량 분포를 분석하고 그 결 과를 처분 안전성 평가에 이용할 수 있는 방안을 제시하였다. 처분 심도의 지하수 유동량은 가상의 처분 부지를 대상으로 한 광역 및 국지적 지하수 유동 모의 결과의 지하수두 분포를 이용하여 분석하였다. 지하수 유동량 분포를 이용하여 처분공 위 치의 지하수 유동량을 분석하고 최대값을 기준으로 지하수 유동량을 표준화하여 처분공에서의 처분 용기 파손 가능성을 확 률적으로 도시하였다. 확률적으로 제시된 처분 용기의 파손 가능성을 이용하여, 처분 용기로부터 누출이 일어날 것으로 가 정된 위치에서 지표 환경으로 이동하는 방사성 핵종의 이동량에 대한 확률론적 기대값을 계산하여 결정론적으로 평가된 이 전 연구 결과와 비교하였다. 이런 평가 방법은 현장 조건을 더욱 많이 반영할 수 있는 안전성 평가 방안 구축에 기여할 수 있 을 것으로 생각된다.

Water discolouration and increased turbidity in the local water service distribution network occurred from hydraulic incidents such as drastic changes of flow and pressure at large consumer. Hydraulic incidents impose extra shear stresses on sediment layers in the network, leading to particle resuspension. Therefore, real time measuring instruments were installed for monitoring the variation of water flow, pressure, turbidity and particulates on a hydrant in front of the inlet point of large apartment complex. In this study, it is attempted to establish a more stable water supply plan and to reduce complaints from customers about water quality in a district metering area. To reduce red or black water, the water flow monitoring and control systems are desperately needed in the point of the larger consumers.

By increasing the flow rate of near the river the water level increases. Due to the increased water level, damage occurs in the revetment. In this paper, In oder to estimate the amount of overtopping rate in the revetment near the river the numerical mode