• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.4
• /
• pp.377-385
• /
• 2013

To identify the effects of an outflow area on pool boiling heat transfer in a vertical annulus, three different flow restrictors were studied experimentally. For the test, a heated tube of smooth stainless steel and water at atmospheric pressure were used. Both annuli with open and closed bottoms were considered. To validate the effects of the outflow area on the heat transfer, the results of the annulus with the restrictor were compared with the data for the plain annulus without the restrictor. The reduction of the outflow area ultimately results in a decrease in the heat transfer. As the outflow area is very small, a slight increase in heat transfer is also observed. The major cause of this tendency is explained as the difference in the intensity of liquid agitation cause by the movement of coalesced bubbles. It is identified that the convective flow, pulsating flow, and evaporative mechanism are considered as the important mechanisms.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.2
• /
• pp.211-217
• /
• 2010

It is important to measure the mechanical properties of nanostructures because they are required to determine the lifetime and reliability of nanodevices developed for various fields. In this study, tensile tests for a multi-walled carbon nanotube (MWCNT) and a ZnO nanorod were performed in a scanning electron microscope (SEM). The force sensor was a cantilever type and was mounted in front of a nanomanipulator placed in the chamber. The nanomanipulator was controlled using a joystick and personal computer. The nanostructures dispersed on the cut area of a transmission electron microscope (TEM) grid were gripped with the force sensor by exposing an electron beam in the SEM; the tensile tests were the performed. The in situ tensile loads of the nanostructure were obtained. After the tensile test, the cross-sectional areas of the nanostructures were observed by TEM and SEM. Based on the TEM and SEM results, the elastic modulus of the MWCNT and ZnO nanorod were calculated to be 0.98 TPa and 55.85 GPa, respectively.

• Korean Chemical Engineering Research
• /
• v.55 no.1
• /
• pp.68-73
• /
• 2017

The removal of particulate matter ranging from $0.01{\mu}m{\sim}10{\mu}m$ can be performed by using membrane filters composed of fibers. Electrospinning techniques offer the production of very thin fibers with a uniform fiber diameter over conventional techniques including template synthesis, melt-blown, phase separation, etc. Air filtration will be improved with electrospun membranes due to the open pore structures, high porosity, and large surface area of the membranes. In the present study, filtration efficiency increased with pore size decrease and fiber density increase induced by carbon nanotube and the increased CA (cellulose acetate) concentration during electrospinning process.

• Journal of Convergence for Information Technology
• /
• v.12 no.3
• /
• pp.141-150
• /
• 2022

Fluid flow and thermal characteristics of laminar nanofluid(water/Al2O3) flow in a circular U-bend tube have been studied numerically. In this study, the effect of Reynolds number and the solid volume fraction and the impact of the U-bend on the flow field, the heat transfer and pressure drop was investigated. Comparisons with previously published experimental works on horizontal curved tubes show good agreements between the results. Heat transfer coefficient increases by increasing the solid volume fraction of nanoparticles as well as Reynolds number. Also, the presence of the secondary flow in the curve plays a key role in increasing the average heat transfer coefficient. However, the pressure drop curve increases significantly in the tubes with the increase in nanoparticles volume fraction.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.4
• /
• pp.329-336
• /
• 2003

Intra-Vascular Ultra-Sound (IVUS) transducers were developed for the application to diagnose coronary diseases. The transducer consists of 32 piezoelectric elements with a front insulation layer and a polymeric acoustic backing layer on a hollow alumina tube. The optimal geometrical structure of the transducer was designed through theoretical analysis of radiation patterns of the transducer. Samples of the IVUS transducers of the diameter of 3㎜ were fabricated to illustrate the design scheme. For the piezoelectric elements, 2-2 mode piezocomposite materials were employed. Experimental performance of the transducers showed good agreement with the design results, which verified feasibility of the transducer for IVUS applications.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.181-185
• /
• 2010

The behavior of combustion-induced internal flow of SRM equipped with fin-slot grain and submerged nozzle is very complex and diverse. Cold air-flow test for 2D and 3D scale models of SRM has been done in order to specify the visualization method to analyze particular internal flow patterns such as roll-torque inducing flow. Swirl flow induced by asymmetric vortical tube also has been visualized through employing various light source and recording directions.

• Proceedings of the KAIS Fall Conference
• /
• 2011.12a
• /
• pp.262-265
• /
• 2011

본 연구는 탈진 기류 분사 시스템의 최적화 설계에 관한 기초 연구의 일환으로 전산유체역학(CFD)을 이용하여 일반 블로우 튜브와 단순 벤츄리 조합의 충격 기류(Pulse air jet) 방식의 탈진 장치에 대한 탈진 성능과 벤츄리 입구에 기류 유도용 구조물을 설치한 경우의 탈진 성능을 비교하였다. 각 Case별로 벤츄리 내부로 유입되는 탈진 공기량을 예측한 결과, case 2의 벤츄리 형상 개조시 case 1 보다 벤츄리로 유입되는 탈진 공기량이 약 20% 증폭되는 것으로 나타났다. 또한 필터백 표면에서의 탈진 기류 전달 분포를 예측한 결과, 모든 case가 필터백의 국한된 영역으로 탈진 기류가 집중됨을 알 수 있었다. 또한, case 2의 경우가 case 1보다 오히려 탈진 기류의 전달 수준이 불량함을 알 수 있다. 이는 case 2의 경우 벤츄리 입구에 기류 유도용 구조물을 설치한 것이 탈진 공기량을 증폭시키는데에는 도움이 되나, 오히려 벤츄리 내부로 유입된 탈진 기류의 직진성을 보완하여 필터백 내부에서 탈진 기류의 확장을 방해하기 때문인 것으로 판단된다.

• Economic and Environmental Geology
• /
• v.48 no.3
• /
• pp.247-253
• /
• 2015

Natural halloysite is mostly found in the form of a tubular structure with a 15-125 nm internal lumen. This kaolin clay can be used for encapsulating a liquid ingredient of cosmetics and for immobilizing an inorganic solid-phase ingredient. In this paper, the encapsulation and immobilization procedures are introduced and two example applications are reviewed to demonstrate the usefulness of halloysite as a cosmetics substrate. It may help attract more interest in cosmetic applications of halloysite and thus spur more research on the utilization of natural clays.

• Analytical Science and Technology
• /
• v.12 no.2
• /
• pp.89-93
• /
• 1999

In this study, conductivity cell and suppressor for micro-column ion chromatography were developed to analyze ions in small columns of samples. With a capillary column, the flow rate of the mobile phase is so small (usually $5{\sim}20{\mu}L/min$) that the usual conductivity cell can not be used. Therefore, we developed a new type of conductivity cell and suppressor which have small inner volumes. The conductivity cell was made with two Pt hypodermic needles (i.d. 0.010 mm) which are slightly separated (about $2{\mu}m$), and the suppressor was made of Nafion tubings. When several anions(fluoride, nitrite, nitrate, chlorate) were analyzed using developed conductivity cell and suppressor, a good chromatogram was obtained.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.4
• /
• pp.1511-1517
• /
• 2012

Vacuum chamber or vacuum tube for the exhaust process of vacuum glazing is presently used, where excessive time and expenses are required to make the whole vacuum chamber or tube vacuum. To solve this problem, multifunction equipment for vacuum exhaust and ultrasonic joining at atmospheric pressure has been developed, in which a piezoelectric vibrator experiences excessive temperature rise resulting in optimizing the cooling of the equipment. Therefore, in this study, cooling effects of natural convection and forced convection methods were identified by numerical analysis and experiments, and cooling performance of the multifunction equipment was optimized.