• Transactions of the Korean Society of Mechanical Engineers
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• v.1 no.1
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• pp.17-25
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• 1977

The purpose of this paper is to clarify the effect of wall proximity on the terminal velocity of single air bubbles in vertical tubes. As an initial step, experiments were conducted to determine the terminal velocity, shape, and path of single air bubbles rising freely in water. The terminal velocity of air bubbles rising through water was measured in cylindrical tubes, rectangular tubes, and parallel plates respectively. The results of effect wall of cylindrical tubes were shown as a dimensionless plot, and may also be used to arrive at a decision regarding the minimum size of tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.12
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• pp.553-558
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• 2014

Geothermal energy can be used with a geothermal heat pump or an earth-to-air heat exchange system (EAHES), which is referred to as a "cooling tube" in Korea. In this study, we suggest EAHES burial guidelines in terms of the parameters of buried pipe length and air velocity regarding the exit air temperature of EAHES. The exit air temperature for EAHES in three regions (Changwon, Busan and Seoul) was calculated with variation in buried pipe length and air velocity at ${\Phi}100mm$ and ${\Phi}200mm$. In conclusion, variation in the buried pipe length is more effective than that of air velocity to achieve the required exit air temperature.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.187-187
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• 2019

서울과 같은 주요 도시지역의 하수관망은 그 규모와 구성이 크고 복잡하여 강우유출모형을 구축하는데 많은 어려움이 발생한다. 또한 많은 연구자들이 직관적으로 관망을 구축하고 단순화하고 있으며, 실무에서는 일정기준 이하의 관망을 일괄적으로 삭제하는 등의 간단한 하수관망 단순화 방법을 사용하여 강우-유출 모형을 구축하고 있다. 따라서 본 연구에서는 서울시의 주요 상습침수 구역인 도림천 유역을 대상으로 전체 하수관망을 구축하고 대상유역의 누가유역면적을 기준으로 모형을 단순화하는 단순화기법과 일정 관경 이하의 하수관을 일괄적으로 삭제하는 단순화방안을 2차원 침수분석 결과를 통해 비교하여 적절한 하수관망 단순화 방안을 찾아보고자 하였다. 각각의 하수관망 단순화 기법을 통해 3가지 규모로 나누어 모형을 단순화 하였으며 도림천 일대에 많은 침수 피해를 발생시킨 2010년 9월 21일 강우사상을 적용하여 각각의 2차원 침수결과를 침수흔적도와 비교하여 규모별 단순화 방안의 적정성을 분석하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.366-374
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• 2014

Experimental mass transfer data, which were obtained for the $CO_2$-water slug flows in vertical tubes with 2, 5, and 8mm diameters, were analyzed in comparison with the penetration theory. It was found that a penetration model with molecular diffusion coefficient cannot predict the experimental data accurately. An effective diffusion coefficient, which considers enhancement effect of interfacial waves, was suggested to improve prediction. Another empirical factor was also suggested to consider the effect of non-uniform interface velocity. A modified penetration model was found to be capable of predicting the experimental data reasonably well.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.493-493
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• 2023

매설배관의 피복손상부 탐측법은 CIPS법, DCVG법 등 여러 방법이 있으며, 그중 우리나라에서는 DCVG법이 가장 많이 사용되고 있다. 피복손상탐측기술(DCVG)은 매설된 관로에 대하여 직류 전류로 인해 배관주변에 발생하는 전위구배를 측정하여 비굴착상태에서 관로의 피복손상부를 찾아내는 기술이다. 본 기술을 광역상수도 정밀안전진단 및 성능평가에 적용하였으며, 탐측된 위치에 대하여 위험도(%IR)를 예측하였다. 또한 손상의심부에 대한 굴착을 통해 피복손상부를 확인하였다. 본 기술의 신뢰성 및 상수도 분야에 큰 활용성을 확인하였다. 관경, 현장여건 등에 따른 조사 및 굴착에 일부 한계점을 보였으나, 향후 축적된 데이터를 바탕으로 매설된 관로의 손상을 사전에 확인하여 관로사고를 미연에 방지할 기술로 판단된다.

• Journal of Korea Water Resources Association
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• v.44 no.10
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• pp.777-786
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• 2011

In the previous researches for storm sewer design, the flow path, pipe diameter and pipe slope were determined to minimize the construction cost. But in the sewer networks, the flows can be changed according to flow path. The current optimal sewer layout models have been focussed on satisfying the design inflow for sewer designs, whereas the models did not consider the occurrences of urban inundation from excessive rainfall events. However, in this research, the sewer networks are determined considering the superposition effect to reduce the inundation risk by controlling and distributing the inflows in sewer pipes. Then, urban inundation can be reduced for excessive rainfall events. An Optimal Sewer Layout Model (OSLM) was developed to control and distribute the inflows in sewer networks and reduce urban inundation. The OSLM uses GA (Genetic Algorithm) to solve the optimal problem for sewer network design and SWMM (Storm Water Management Model) to hydraulic analysis. This model was applied to Hagye basin with 44 ha. As the applied results, in the optimal sewer network, the peak outflow at outlet was reduced to 7.1% for the design rainfall event with 30 minutes rainfall duration versus that of current sewer network, and the inundation occurrence was reduced to 24.2% for the rainfall event with 20 years frequency and 1 hour duration.

• Journal of Korean Society for Geospatial Information Science
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• v.4 no.2 s.8
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• pp.55-61
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• 1996

The objective of this paper is to show an optimal design model for branched water supply system which also can find the optimal location of pumping stations using linear programming. GIS is utilized in this model to better handle the data and the results front the optimization. The developed model considers hydraulic influences of some appurtenances such as supply tunnels and a filtration plant The model also considers tunnel construction cost which should be treated differently from pipe construction cost Different from other models presently available, the model guarantees a nonnegative pressure at every junction node in the system. The objective function includes annual operation cost (electricity rate) ill addition to initial construction cost, thus producing a more reasonable decision. The model selects the optimal diameter not in the form of continuous number but in the form of commercial discrete diameter (pipe size) using the pipe lengths as decision variables instead of pipe diameters. The model not only determines the optimal pumping head for each pumping station but also finds the optimal location and number of pumping stations. GIS is used to handle hydraulic and budgetary data automatically and to visualize the results for the of optimal design of the system. The model has been applied to an existing water supply system. 'The results show that the optimization model with the aid of GIS is helpful in the decision-nulling process for the design of more economical systems, and can be dot into practice successfully.

• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.1-12
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• 2006

An existing Steel pipe, Cast iron pipe and Concrete pipe is can not escaped from aging, specially Metal tube is causing many problems that the quality of water worse is concerned about many rust and mike efficient use of preservation of water. The use of Glassfiber Reinforced Plastic Pipe(GRP PIPE) should be one of the possible scheme to get over these problems. The GRP PIPE has an excellent resistance power and the life is lasting from 50 to 100 years roughly. It's to be useful as a result of high durability and a good construction work also it is a light weight therefore can be expected to short the time of construction and man power. In this research, to executed the small-scaled model test, in-situ model test using CLSM of in-situ soil and to evaluated the stress - strain of the pipe also try to estimated how useful is. From the model test in laboratory, the vertical and horizontal deformation of the GRP PIPE measured in six instance using 200mm and 300mm in diameters. The value of experimentation, theory, analysis got the same results of the test, but the vertical and horizontal deformation gauged in small and the earth pressure was almost zero using CLSM of in-situ soil..

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.1-7
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• 2009

Most developed models are designed to determine pipe diameter, slope and overall layout in order to minimize the cost for the design rainfall for the optimal sewer layout. However, these models are not capable of considering the superposition effect of runoff hydrographs in the sewer pipes. The flow characteristics in the sewer pipes, such as the sewer layout, pipe diameter and slope, vary according to the design of the sewer system. In particular, when the sewer network is modified, the shapes of the runoff hydrographs in the sewer pipes also change because of the superposition effect. In this study, the sewer layout is designed to control and distribute the flows in the sewer pipes, while considering the runoff superposition effect, in order to reduce the inundation risk at each junction. This is accomplished by separating the inflows that enter into each junction by changing the way in which pipes are connected between junctions. And this model combines SWMM (Storm Water Management Model) to perform the hydraulic analysis for the flows in the sewer network. The current sewer layout was modified to minimize the peak outflow at outlet in Garak basin, Seoul, South Korea. As the results, the peak outflows at the outlet were decreased by approximately 20% for the design rainfall during 30 minutes and the total overflows were also decreased for the excessive rainfalls.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.1-6
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• 2023

PE piping, which has advantages in terms of construction convenience and economy, is widely used for underground burial in the domestic urban gas field. These PE pipes use squeeze-off in many sites to block gas flow during maintenance and repair work. Squeeze-off refers to a method of compressing a PE pipe to block fluid flow, and damage may occur due to the nature of construction in which the pipe is deformed by physical force. In order to prevent damage to PE pipes due to squeeze-off, the main points to be reflected in the squeeze-off operation procedures such as proper compression range, use pressure, and diameter were derived through damage assessment and confidential test according to the compression rate. The compression experiment for PE pipe damage assessment was conducted while changing the compression rate (20%~40%), the pressure of use (2.8 kPa, 25 kPa, 70 kPa), and the pipe diameters (63 mm, 90 mm, 110 mm). As a result of damage assessment according to the compression rate, damage occurred in pipes with compression rates of 45%(110mm) and 73%(63mm), which are for analyzing the effect of excessive compression. In addition, the leakage test was conducted using Ar(argon) during the squeeze-off, and as a result of the experiment, leakage occurred under the conditions of 70kPa and 110mm of pipe. As a result of this study, it was confirmed that squeeze-off for airtightness should be carried out in pipes within a range not exceeding 25 kPa and 90 mm pipes, and the appropriate compression rate to prevent damage to PE pipes is 30%.