• 에너지공학
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• 제13권4호
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• pp.275-280
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• 2004

관내부로 흐르는 물에 초음파 진동을 가진 하였을 때 관내 열전달이 증진되는 효과를 실험 및 수치해석을 통해 연구하였다 원형관 벽면에서 관내부로 흐르는 물로의 대류 열 전달계수를 초음파 진동이 있을 때 와 없을 때에 측정하였다. 이 결과를 비교함으로써 초음파진동이 전열성능 향상에 미치는 영향을 정량화 하였다. 이러한 현상에 영향을 줄 수 있는 유량과 온도의 범위를 넓히기 위하여 수치해석을 수행하였다. FLUENT 6.1을 이용하여 관내의 유동장과 온도분포를 해석하고 초음파 진동 유무 시 대류 열 전달계수를 평가하였다 연구결과 초음파진동이 강제대류 조건에서 전열성능을 향상시키며 그 영향은 관내를 흐르는 물의 유량에 따라 크게 변한다는 것을 보여주고 있다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.277-282
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• 2006

In order to predict the indoor air pollutant, the VOCs emission rate is used through small chamber in the design process. However, the small chamber method has limitations as the convective mass transfer coefficient, the most important factor when predicting VOCs contamination of indoor air, is different between the small chamber result and the measured data in the actual building. Furthermore, the existing studies which analyzed mass transfer coefficient in the small chamber were directed on the small chambers developed at the time and FLEC(Field and Laboratory Emission Cell), thus, are different from the current small chamber which has been changed with improvements. The purpose of this study is to determine the emission rate of pollutant in double-layered building materials through the CFD(Computational of Fluid Dynamics) and Numerical analysis based on the mass transfer coefficient on singled-layered building material by using the current small chamber widely used in Korea. Futhermore, this study used the new convective mass transfer coefficient($h_m'$) which indicates the existing convective mass transfer coefficient($h_m$) including VOC partition coefficient(k). Also, formaldehyde was selected as target pollutant.

• 한국지열·수열에너지학회논문집
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• 제14권4호
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• pp.20-26
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• 2018

In this study, the performance characteristics of a welded plate heat exchanger was investigated experimentally. Performance tests were carried out according to the flow rate and inlet temperature of working fluid. As a result, the heat transfer capacity increased by 335.5 kW with an increasing the flow rate and temperature difference between hot and cold side. However, the overall heat transfer coefficient was increased with the increase of flow rate, and it was not effected significantly from inlet temperature difference between hot and cold working fluid. The pressure drop was increased by 55.78 kPa with an increasing the frow rate when the flow rate ratio between hot and cold side 1:1. However, the tendency of pressure drop was difference when flow rate ratio wasn't 1:1. In case that the flow rate ratio between hot and cold side was not 1:1, the pressure drop at the low flow rate side was higher than that when the flow rate ratio was 1:1, while pressure drop of the other side was decreased compared to that when the flow rate ratio was 1:1.

• 대한기계학회논문집B
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• 제28권3호
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• pp.338-348
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• 2004

The present study is conducted to investigate the effect of rib arrangements on an impingement/effusion cooling system with initial crossflow. To simulate the impingement/effusion cooling system, two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of tile hole diameter. Initial crossflow passes between the injection and effusion plates, and the square ribs (3mm) are installed on the effusion plate. Both the injection and effusion hole diameters are 10mmand Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6 times of the hole diameter, respectively. To investigate the effects of rib arrangements, various rib arrangements, such as 90$^{\circ}$transverse and 45$^{\circ}$angled rib arrangements, are used. Also, the effects of flow rate ratio of crossflow to impinging jets are investigated. With the initial crossflow, locally low transfer regions are formed because the wall jets are swept away, and level of heat transfer rate get decreased with increasing flow rate of crossflow. When the ribs are installed on the effusion plate, the local distributions of heat/mass transfer coefficients around the effusion holes are changed. The local heat/mass transfer around the stagnation regions and the effusion holes are affected by the rib positions, angle of attack and rib spacing. For low blowing ratio, the ribs have adverse effects on heat/mass transfer, but for higher blowing ratios, higher and more uniform heat transfer coefficient distributions are obtained than the case without ribs because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. Average heat transfer coefficients with rib turbulators are approximately 10% higher than that without ribs, and the higher values are obtained with small pitch of ribs. However, the attack angle of the rib has little influence on the average heat/mass transfer.

• 한국수정란이식학회지
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• 제18권2호
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• pp.97-108
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• 2003

체외수정된 한우 수정란을 PCR 기법에 의한 성감별을 위해 생검하여 회복시까지 1∼2시간 동안 배양하였다. 이 성감별된 한우 수정란을 2000년 2월부터 2001년 2월까지 한우 49두와 젖소 16두에 이식하였다. 수정란이 이식된 65두의 수란우중 14두(한두 12두, 젖소 2두)가 성감별 결과와 동일한 성의 산자를 생산하였고, 전체 수태율은 21.5%를 나타내었다. 1. 총 65두의 수란우중 웅성 수정란은 35두에 자성 수정란은 30두에 이식되었고 이중 분만된 산자 14두중 웅성은 6두, 자성은 8두였으며 PCR에 의한 성감별 정확도는 100.0%를 나타내었다. 2. 성감별된 한우 수정란은 한우와 젖소에 이식한 후 수태율은 각각 24.5, 12.5%를 나타내었다. 3. 성감별된 한우의 신선수정란과 동결-융해된 수정란의 이식후 수태율은 각각 23.5, 14.3%를 나타내었다. 4. 성감별된 한우 수정란의 이식 시기에 따른 수태율은 봄, 여름, 가을, 겨울에 각각 11.8, 29.4, 23.4, 20.0%를 나타내었다 5. 성감별된 한우 수정란의 상태에 따른 이식후 수태율은 excellent, good, fair군에서 각각 41.7, 30.0, 0.0%를 나타내었다. 6. 성감별된 한우 수정란의 이식시 수란우의 자궁각 두께에 따른 이식후 수태율은 0, +, ++, +++군에서 각각 71.4, 18.9, 11.8, 0.0%를 나타내었다. 7. 성감별된 한우 수정란이 주입된 수란우 자궁각 부위에 따른 이식후 수태율은 자궁각 선단부, 중심부, 미부에서 각각 30.0, 20.0, 10.0%를 나타내었다. 8. 성감별된 한우 수정란의 이식시 수란우의 황체의 상태에 따른 이식후 수태율은 excellent, good, poor군에서 각각 41.2, 14.3, 15.4%를 나타내었다. 9. 성감별된 한우 수정란을 straw에 장착후 이식시까지 10, 15, 20, 25, 30분 경과에 따른 이식후 수태율은 18.2, 30.0, 30.0, 0.0, 25.0%를 나타내었다. 10. 성감별된 한우 수정란의 이식시 수란우의 산차에 따른 이식후 수태율은 1산차, 2산차, 3산차, 4산차에서 각각 26.5, 19.1, 14.3, 0.0%를 나타내었다. 이상의 결과에서 성감별된 수정란의 이식시 양호한 수태율을 얻기 위해서는, 신선수정란이 동결수정란 보다 유리하다는 점과 생검후 수정란의 회복상태, 수란우의 자궁각 두께, 수정란의 수란우 자궁각 주입부위, 수란우의 황체 상태, 이식시까지 소요시간, 수란우의 산차를 고려해야 한다는 것을 알 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.272-277
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• 2000

The heat transfer characteristics of confined turbulent slot jet impingement on the flat plate with square rods(turbulence promoter) have been experimentally investigated at different nozzle configuration. The effects of jet Reynolds number (Re=3900, 5800, 7800, 9700), dimensionless slot-to-plate distance(H/B=4, 6, 8) and clearance(c) between square rods and the plate were examined. Measurement of heat transfer rate were conducted using naphthalene sublimation technique. When square rods were inserted over the heat transfer surface, heat transfer rate was slightly increased in the wall jet region and the sharp-edged orifice nozzle was heigher than squared orifice nozzle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.119-124
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• 2000

The heat transfer characteristics of confined turbulent slot jet impingement on the flat plate with square rods(turbulence promoter) have been experimentally investigated. The effects of jet Reynolds number (Re=3900, 5800, 7800, 9700), dimensionless slot-to-plate distance(H/B=4, 6, 8) clearance(c) between square rods and the plate, and the length(d) of a side of the square rod were examined. Measurement or heat transfer rate were conducted using naphthalene sublimation technique. When square rods were inserted over the heat transfer surface, heat transfer rate was slightly increased in the wall jet region.

• 설비공학논문집
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• 제14권6호
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• pp.485-492
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• 2002

Heat transfer and pressure drop on the air side of a plate-louvered fin heat exchanger with new shape of louver fin have been investigated experimentally. Water is employed inside the flat tube to transfer heat with air for convenience. This problem is of particular interest in the design of a plate-louvered heat exchanger. The effect of air flow rate, water flow rate and water temperature on pressure drop as well as heat transfer in air side are studied in detail. The present results showed a good agreement qualitatively with the previous results in general. Based on the experimental data, f-factor and j -factor correlations of the present louvered-fin are suggested. It is also found that heat transfer could be enhanced with new shape of louver fin, compared with the conventional louvered-fin, while the f-factor remains unchanged.

• 설비공학논문집
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• 제1권2호
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• pp.182-189
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• 1989

The propose of this study is augmentation of heat transfer without additional external power in 2-dimensional impinging air jet. The passive heat transfer augmentation method tried in this experimental study is placement of rod bundles with the clearance, 2mm, in front of the heat transfer surface. The effects of pitch distance among rods and nozzle-to-target plate distance are investigated. The overall heat transfer rate of flat plate with rods reaches maximum at H/B=10 and P=40mm, and for H/B=2 and P=40mm the augmentation rate of heat transfer becomes maximum to a value which is about 1.57 times that of the flat plate without rods.

• 한국도로학회논문집
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• 제16권3호
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• pp.9-20
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• 2014

PURPOSES : This study is to compare load transfer efficiency of key joint and dowel joint for airport concrete pavement. METHODS : As AC150/5320-6D of FAA's [Advisory Circular] was changed into AC150/5320-6E, Key joint type of rigid pavement were excluded from Construction Joints. LTE(Load Transfer Efficiency) of dowel joint and key joint were compared by times and seasons through pavement temperature measurement, ocular investigation and HWD measurement. RESULTS : For the joint performance grade of No. 2(The second) runway of airport, 12% of poor rate was observed in key joint and 2% of poor rate in dowel joint. Poor rate of key joint was increased to 17%, if only No. 3~No. 6 slabs, which are mostly loaded from the airplanes, were applied for the study. In apron area, LTE poor rate of key joint was high in winter, and LTE poor rate of dowel joint was at least above 'Fair' grade. In summer, 'Fair' for key joint, 'Acceptable' for dowel joint appeared. CONCLUSIONS : As results, dowel joint was superior than key joint for LTE. Deviations of seasons and times were smaller in dowel joint's result. And LTE in winter was lower than LTE in summer.