• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.203-209
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• 2016

According to the wear detection history for the steam generator tubes in the nuclear power plant, the outer tubes inside the steam generator have more problems on the flow-induced vibration than inner tubes. Many researchers and engineers have used a specified added mass coefficient for a given tube array during the design stage of the steam generator even though the coefficient is not constant for entire tube in cylindrical shell. The aim of this study is to find out the distribution of added mass coefficients for each tube along the radial location. When numbers of tubes inside a cylindrical shell are increased, values of added mass coefficients are also increased. Added mass coefficients at outer tubes are less than those of inner tubes and they are decreased with increasing the gap between the outermost tube and the cylindrical shell. It also turns out when the gap between the outermost tube and the cylindrical shell approaches infinite value, the added mass coefficient converges to an asymptotic value of given tube array in a free fluid field.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.537-544
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• 2008

In this paper, flow characteristics of an adiabatic capillary tube in a transcritical $CO_2$ have been investigated employing the homogeneous model. The model is based on fundamental equations of mass, energy and momentum which are solved simultaneously. Two friction factors(Churchill) and viscosity(McAdams) are comparatively used to investigate the flow characteristics. Supercritical and subcritical thermodynamic and transport properties of $CO_2$ are calculated employing EES property code. Flow characteristics analysis of $CO_2$ adiabatic capillary tube is presented to offer the basic design data for the operating parameters. The operating parameters considered in this study include inlet temperature and pressure of an adiabatic capillary tube, evaporating temperature and inner diameter tube. The main results were summarized as follows : inlet temperature and pressure of an adiabatic capillary tube, evaporating temperature, mass flowrate and inner diameter of $CO_2$ adiabatic capillary tube have an effect on length of an adiabatic capillary tube.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.46-50
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• 2004

The Experimental results of the in-line type inertance tube pulse tube cryocooler for cooling superconductor RF filter are presented in this paper. The pulse tube refrigerator, which has no moving parts at its cold section, is attractive in obtaining higher reliability, simpler construction, and lower vibration than any other small refrigerators. The purpose of this study is to analyze the characteristics of in-line type inertance tube pulse tube refrigerator (IPTR), and to get main factor to improve the performance of the in-line type IPTR. Firstly, design parameters of the in-line IPTR are discussed by ARCOPTR program, and then to find optimal conditions of in-line type IPTR, cool down characteristics according to the variations of the charging pressure, inertance tube volume, regenerator volume and pulse tube volume are measured by the experiment. The lowest temperature of the cold end was about 50 K. Cooling capacity was the highest in the charging pressure of 32 atm. and 5W at 72K. On the other hand, COP of the in-line type IPTR was the highest in the charging pressure of 21 atm. and 0.018 at 77K.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.1023-1031
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• 1989

An experimental study is conducted to investigate the turbulent wake flow around tubes in vertical single row tube banks. All measurements are performed at Reynolds number(Re$_{max}$) 4.2*10$_{3}$ - 2.5*10$_{4}$ with varying tube spacings from the wide pitch ratio(H/D=3.07) to the very narrow one(H/D=1.23). Flow patterns are visualized using the smoke-wire method. Mean static pressures, velocity components, and various statistical quantities of turbulence are obtained by the computer on-line technique. In the case of wide tube spacings, the near wakes of tube show similar trends to those of a single tube, and their flow indicats an anisotropic turbulence. However, as the pitch ratio decreases, wide and narrow wakes appear alternately behind adjacent tubes due to the deflected flow. Also, in the case of H/D .leq. 1.54, Karman vortex is not formed at the side of relatively wide wake.e.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.254-260
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• 2002

There have been many studies for the flow through internally finned tube, since the heat exchangers with fin device derive much attention in heat transfer enhance cent. In this study, analysis of laminar flow through the circular tube with longitudinal fins are investigated. The height and the number of fins are arbitrary. The flow field is assumed to be laminar and conformal mapping is used to obtain analytic solution. From the analytic solution, equi-velocity lines are shown, and the flow rate through the finned tube is calculated for various fin heights and numbers of fins. Darcy friction factor for this finned tube and shear stress distributions on the wall and fin are also considered.

• Journal of Power System Engineering
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• v.13 no.2
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• pp.49-55
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• 2009

Recently, a study on condensers for refrigerators has focused on new model which will cost less and will be more efficient. Some widely used condensers for domestic refrigerators are wire-and-tube type condenser, hot-wall type condenser, and spiral type condenser. Some companies which use the spiral type condenser at the moment try to develop a new tube-and-plate type condenser which will cost less and will be as efficient as the spiral type. As a standard condenser type, tube-and-plate type condenser is used in this study. A two-dimensional numerical model for the tube-and-plate type condenser is proposed, and the flow and heat transfer characteristics for several types of condensers are investigated.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.42-47
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• 2020

YouTube, the online video streaming platform, has become popular and influential around the globe. Due to the development of science and technology, people without expertise in filming can now easily produce their videos with unique content. Many people are more eager to become a popular YouTube creator because they can earn money by placing commercials or Products in Placement (PPL) in their video clips. However, it is yet unknown what genres of YouTube videos are popular. YouTube creators have their channels where they upload videos of a certain type of genre. This study investigates video genres of the top 250 YouTube channels in English-speaking countries (United States, Canada, United Kingdom, and Australia) using Social Blade, which is a research website. The ranking is set based on the number of times people watched a video ("Video Views"). We handsomely analyze popular genres of the channels and also the YouTube ecosystem, and it will be meaningful for today's new media era.

• International journal of advanced smart convergence
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• v.9 no.3
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• pp.28-35
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• 2020

YouTube has been gaining popularity all around the world. A lot of companies have created their own YouTube channels to leverage them in diverse ways; they upload commercial videos, show people user reviews, and conduct promotions with their products. Sports clubs are no exception; they upload diverse videos to gain popularity and to interact with their fans. This study analyzes how the English Premier League (EPL) clubs leverage their YouTube channel as soccer (football in European nations) players. YouTube activities of 20 clubs during the 2019/2020 Season are investigated. After careful consideration, we decide to examine two factors of the respective channel of the YouTube: 1) Popularity (the number of views and subscribers) 2) Contents of videos (e.g. interviews and highlight scenes). The study followingly inspects the benefits of utilizing YouTube channels and of direct communication between sports clubs and fans in online settings.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.68-71
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• 2007

A computational study has been performed using a chimera scheme to study the various operating processes inside a ballistic range. The compression flow fields in the pump tube and projectile motion in the launch tube are captured for various piston masses and diaphragm rupture pressures. The effect of a shock tube in between the pump tube and launch tube is analyzed. The results are compared with available experimental data. It is noted that, by adding a shock tube in between the pump tube and launch tube, the peak pressure in the ballistic range can be reduced without appreciable reduction in the velocity of the projectile.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1168-1173
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• 2003

When the tube contacted to support and antivibration bar of the steam generator in unclear power plant, the contact area is worn out by their relative displacement. In the study, wear depths of the tube inclined to tube support and antivibration bar are approximately predicted by a method using the contact load and relative displacement. In the case of the inclined contact, the results show wear depths of the steam generator tube predicted by the impact model are larger than those by the sliding model.