• 한국기계가공학회지
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• 제18권2호
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• pp.7-13
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• 2019

This study is about distributions of heat transfer in air conditioning duct used for marine and oil drilling ship. As the convective heat transfer coefficient increased, heat transfer was conducted dynamically to inside as it exited to the outlet of duct. So, it was checked that the amount of heat transfer generated at duct increased as the convective heat transfer coefficient increased. In case the convective heat transfer coefficient was low, the temperature of duct showed the relatively high temperature distribution due to the temperature influence of internal fluid as the heat transfer between the outside and inside of the duct. In case of temperature distribution generated the volume of the duct along the change of the convective heat transfer coefficient, it was found out that the temperature descended as heat transfer was promoted and the convective heat transfer coefficient increased.

• 터널과지하공간
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• 제22권4호
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• pp.257-265
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• 2012

본 연구에서는 드릴비트 내부 유로의 최적설계를 위하여 암분유동해석을 수행하였다. 이를 위해 암분과 기체의 다상유동해석이 가능한 전산유체역학 코드인 Star-CCM+을 사용하였다. 실제 천공시험으로부터 획득한 결과값을 기체 및 암분의 해석조건으로 적용하였다. 내부 유로 설계에 관련된 핵심인자를 3가지로 결정한 후, 다구찌 기법을 활용한 실험계획법으로부터 3가지 설계인자에 대한 최적값을 조사하였다.

• 한국기계가공학회지
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• 제15권6호
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• pp.77-82
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• 2016

When drilling through Inconel 601 nickel-chromium-based alloys, a large amount of cutting oil is required to prevent tools from wear and fracturing due to heat buildup resulting from the high temperature resistance and toughness of this alloy. However, cutting oil supply has become a factor compromising the machining environment, and this has caused attention to shift to a more environmentally friendly cutting fluid supply system called minimum quantity lubrication (MQL). Our aim in this study was to find a more efficient drill processing method using MQL, and to verify its performance. To that end, we proposed a sealed cover, a step feed, and POSS-type cutting oil as measures to increase the effectiveness of MQL in view of the cutting force and tool wear, and established an improvement in efficiency using the proposed measures.

• 드라이브 ㆍ 컨트롤
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• 제14권2호
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• pp.45-51
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• 2017

Semi-submersible drilling rigs are offshore plants that perform functions such as ocean exploration for oil and gas acquisition, drilling and production, and storage and unloading of crude oil and gas. Semi-submersible drilling rigs use watertight dampers as emergency buoyancy holders. Since the watertight damper is an emergency shutoff device, it is mainly driven by a pneumatic driving system that can operate without a power supply. The pneumatic driving system has highly non-linear characteristics due to compressibility of air and external disturbance such as static and Coulomb friction. In this paper, a new control algorithm is proposed for a watertight damper driving system based on the sliding mode control with a disturbance observer. To evaluate control performance and robust stability of the designed controller, the control results were compared with the results obtained using the state feedback controller. As a result, it was confirmed that the pneumatic driving system for driving the watertight damper using the sliding mode controller with a disturbance observer can obtain excellent control performance against the parameter changes and the disturbance input.

• 대한조선학회논문집
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• 제32권2호
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• pp.84-92
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• 1995

석유시추공에서 저주파음향의 전파특성을 파악하기 위하여, 무한히 길고, 균일한 단면을 갖고, 유체와 고체로 구성된 원통형 다층 음향도파관에 대한 이론적 해석을 수행하여, 각 층들의 연성작용을 고려한 음향의 전파모드, 전파속도를 구했다. 저주파수(음향파의 파장이 시추공 지름에 비해 매우 크다), 축대칭, 비점성유체 등의 가정을 함으로써 해석적 해를 얻을 수 있었다. 또한 그 결과를 이용하여 단면의 변화가 있는 곳에서의 반사를 해석하는 기법을 제시하였다. 각 층간의 연성이 심한 경우와 연성이 무시될 수 있는 경우에 대한 실제 해석을 통하여 본 기법의 유용성을 확인하였으며, 유한요소법으로 해석한 결과와의 비교를 통하여 본 기법을 검증하였다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
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• pp.145-150
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• 1999

As proven petroleum reserves decline through continued production. exploration for new oil and gas resources will extend into environments which present significant economic risks arid technical hurdles. Since safety is one of the biggest concerns in drilling operations. the oil industry routinely trains its personnel in areas which are critical for safe and economical drilling procedures. One of these major areas is well control. A kick is defined as an unscheduled flow of formation fluids into a wellhole. A kick occurs whenever the resultant wellbore pressure is less than the formation pressure in an exposed zone capable of producing kick fluids. The typical causes of reduced wellbore pressure are insufficient mud weight. inadequate fluid level in the hole, and swabbing.(omitted)

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3390-3397
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• 2022

Among the different techniques available, nuclear methods, including gamma-gamma logging tools, are of special importance. Though the real environment which surrounds the drilled borehole is a complex fractured medium which the fluid can flow through the porosities, simulation studies generally use the traditional model of a homogeneous mixture of formation and the liquid. Considering a previously published study, which shows that modeling of fluid flow in fractured reservoirs and simulating the formation as an inhomogeneous fractured medium leads to different results compared with those of homogeneous mixture, here we study the effect of the presence of drilling fluid (mudcake) on the response of the detectors in both the models. To study this effect, a typical gamma-gamma logging tool was modeled by using the MCNPX Monte Carlo code. The results show that the responses of the detectors in the mixture model in the presence of various thicknesses of mudcake are sensitive to the density of the formation material. However, this effect is not notable in the inhomogeneous fractured medium. These results emphasize the importance of the model employed for simulation of the medium in gamma-gamma well-logging.

• 대한기계학회논문집B
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• 제26권2호
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• pp.318-327
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• 2002

In this paper, heat transfer and pressure oscillation characteristics on oscillating capillary tube heat pipe(OCHP) according to input heat flux, mixture ratio of working fluid and inclination angle were investigated and were compared single working fluid(R-142b) with binary mixture working fluid(R-142b-Ethano1). OCHP was made to serpentine structure of loop type with 10 turns by drilling the channels of length 220mm, width 1.5mm, and depth 1.5mm on the surface of brass plate. In this study, R-l42b and R-l42b-Ethanol were used as working fluids, the charging ratio of working fluids was 40(vol.%), the input heat flux to evaporating section was changed from 0.3W/㎠ to 1.8W/㎠, and mixture ratio of working fluid was R(100%), R(95%)-E(5%), R(90%)-E(10%), and R(85%)-E(15%). From the experimental results, it was found that the effective thermal conductivity of single working fluid was better than that of binary mixture working fluid. But, in case of binary mixture working fluid, critical heat flux was higher than that of single working fluid. And, the higher the mixture ratios of working fluid, the lower heat transfer performance. In case of pressure oscillation, as the inclination angle was lower, pressure wave was more irregular. These phenomena were more serious when the working fluid was binary mixture. Besides, when mixture ratio was higher, saturated pressure was increased, more irregular wave was observed and the mean amplitude was increased. For the same input heat flux, inclination angle and charging ratio, when pressure oscillation has sinusoidal wave, mean amplitude was small, and saturated pressure was low value, the heat transfer was excellent.

• 해양환경안전학회지
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• 제24권5호
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• pp.611-618
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• 2018

본 연구에서는 이수의 유동 특성을 분석하기 위한 기초 연구로서 상용 코드인 ANSYS CFX 14.5를 이용하여 고체-액체 2상 유동에 대한 수치해석적 연구를 수행하였다. 고체-액체 2상 유동 현상을 모사하기 위해서 균질류 모델과 분리류 모델을 사용하였다. 분리류 모델에서는 Gidaspow의 항력모델을 적용하였으며, 고체 입자에 운동 이론 모델을 적용하였다. 기존의 실험 결과를 기반으로 본 연구에서 사용한 수치해석 모델의 유효성을 검토하였으며, 수치해석은 직경 54.9 mm, 길이 3 m의 수평관에서 체적 분율 0.1~0.5, 속도 1~5 m/s 범위에서 수행되었다. 그리고 압력강하와 고체 입자의 체적 분율 분포를 확인하였으며, 압력강하는 균질류 모델과 분리류 모델이 각각 MAE 17.04 %, 8.98 % 이내에서 실험결과를 잘 예측하였다. 관의 하부에서 높은 체적 분율이 나타나며, 상부로 갈수록 체적 분율은 감소하였다. 그리고 속도가 증가할수록 높이 변화에 따른 체적 분율 분포의 변화는 감소하였으며, 수치해석 결과는 이러한 유동 특성을 잘 예측하였다.

• 소음진동
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• 제6권1호
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• pp.65-70
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• 1996

유체와 접한 판재에 박힌 압전센서의 응답을 복합적인 유한요소 해석기법을 이용하여 모델링 하였다. 판재 구조물은 유체영역에서 전파되는 음향파에 의해서 가진된다. 구조물과 압전소자 주위의 유에부분을 유한요소기법을 써서 모델링였고 임의로 나눈 가상경계에서는 평면과 해를 적용하여 변위를 일치 시켰다. 또한, 이 경계에서 변위의 번분까지도 Penalty factor를 써서 일치 시켰으며 가상경계에서의 투명성을 증가시키기 위해서 유한요소의 각 절점에 회전자유도를 추가시켰다. 압전 센서 응답의 수치 결과가 구하여졌고 이것은 센서의 삽입효과가 적을 뿐만 아니라 구조물의 특성에 민감하다는 것이 밝혀졌다.