An Experimental Study on the Heat Flow of Tube Furnace by Air Flow in Tube

Byungsuk Park,Seokmin Hong,Jaewon Lee,Sangwoon Kwon,Juho Lee,Changhwa Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

In this paper, a basic study was conducted to observe the temperature inside the tube according to the heating temperature of the tube furnace. In a tube furnace, a tube is inserted, and the air space outside the tube is heated to increase the temperature of the gas inside the tube through conduction of the tube. Tube furnaces are widely used in research to capture volatile nuclides. In this case, a volatile nuclide capturing filter is inserted inside the tube, and an appropriate temperature is required to capture it. Since the tube furnace heats the air space outside the tube to the target temperature, a difference from the temperature inside the tube occurs. In particular, if a flow of gas occurs inside the tube, a larger temperature difference may occur. In order to confirm this temperature difference, an experimental device was constructed, and basic data was produced through several experiments. The following studies were conducted to produce data. First, the temperature of the air layer of the heating unit and the temperature inside the tube were measured in real time in the absence of gas flow inside the tube. Second, the temperature of the air layer of the heating unit and the temperature inside the tube were measured in real time while air having a certain temperature was flowing inside the tube. As a result of the experiment, when there is no flow inside the tube, when the heating target temperature is low, the temperature inside the tube is significantly lower than the target temperature, and when the target temperature is high, the temperature inside the tube approaches the target temperature. It was found that when there is about 20°C air flow inside the tube, the temperature inside the tube is significantly lowered even if the heating target temperature is high. In the future, additional research on changing the temperature of the gas flowing inside the tube will be conducted, and the results of this study are expected to greatly contribute to the design of a tube furnace that captures volatile nuclides.

증기발생기 전열관지지판의 축균열 파열억제 효과 분석

강용석 ( Yong Seok Kang ),이국희 ( Kuk Hee Lee ),김홍덕 ( Hong Deok Kim ),박재학 ( Jai Hak Park ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.4

A steam generator tubing is one of the main pressure boundary of the reactor coolant system in the nuclear power plants. Structural integrity refers to maintaining adequate margins against failure of the tubing. Burst pressure of a tube at tube support plate can be higher than that for a free-span tube because failure behaviors could be interfered from the tube support plate. Alternative repair criteria for out-diameter stress corrosion cracking indications in tubes to the drilled type tube support plate were developed, however, there are very limited information to the eggcrate type tube support plate. This paper discussed reinforcement effect of steam generator tube burst pressure with axial out-diameter stress corrosion cracking within an eggcrate type tube support plate. A series of tube burst tests were performed under the room temperature and it was found out that there is no significant but marginal effects.

Tube-in-Tube 미세관내 R-22 및 R-407C의 응축열전달 특성

최광일(Kwang-Il Choi),오종택(Jong-Taek Oh) 대한설비공학회 2021 설비공학 논문집 Vol.33 No.2

This paper focuses on the results of an experimental study of condensation heat transfer coefficients with the refrigerants R-22 and R-407C, and looks at the pressure gradient and heat transfer coefficients of horizontal tube-in-tube heat exchangers with the use of small tubes with inner diameters of 4 mm, 3 mm and 2 mm, in a 16.91 mm tube and length of 3,000 mm. Experiments were performed at an inlet saturation temperature of 35 to 45℃ and mass flux ranges from 200 to 600 kg/m²s. The use of an inner tube with a diameter of 4.0 mm resulted in a pressure gradient that was 2.5 times higher than that of an inner tube with a diameter of 8.0mm. In tube-in-tube HEX, the pressure gradients of R-22 measured higher than those of R-407C. The condensation heat transfer coefficients increase with an increase in mass flux, but they decrease with an increase in saturation temperature. Condensation heat transfer coefficients of R-407C were a little higher than those of R-22, and the condensation heat transfer coefficients of double tube HEX were about 40% higher than those of tube-in-tube HEX. The experimental results of this study were also compared with five existing correlations. New condensation heat transfer correlations were developed, and successfully predicted the experimental results with mean deviations of 10.6% and 10.1%, and average deviations are -0.92% and -0.31%, for R-22 and R-407C, respectively.

Tube angle을 이용한 요추 사방향 (Lumbar spine oblique) 검사의 유용성 평가

성동찬(Dong-chan Sung),정지상(Ji-sang Jung),김성식(Sung-sik Kim):박남이(Nam-lee Park),박순규(Sun-kyu Park),안치복(Chi-bok Ahn),임재식(Jae-sik Lim) 대한영상의학기술학회 2017 대한영상의학기술학회 논문지 Vol.2017 No.1

목 적:요추 사방향 검사의 검사 자세는 척추 손상을 가진 환자 또는 그 손상이 의심되는 환자가 하기엔 다소 무리가 있다. 또한 검사과정에서 손상부위의 척추에 무리를 주게 되어 오히려 상태를 더 악화 시킬 가능성 또한 존재한다. 이에 본 연구는 환자의 자세 변화를 최소화하며, tube의 angle을 이용해 진단에 유용한 L-spine oblique 영상을 획득하는 데 목적이 있다. 대상 및 방법:abdomen phantom을 사용하여 약 40° oblique 시킨 후 영상을 획득하였다. 검사 조건은 80kV, 32mAs, 50msec로 고정하였으며, tube angle 은 0°, SID(Source-to-Image-Distance, 이하 SID)는 110 cm로 기준 영상을 획득하였다. 이에 비교 영상으로 SID는 110 cm으로 고정하고, tube의 축을 90° 회전 시켜, phantom을 oblique 시키는 대신 tube angle을 detector에 15~30°까지 5°씩 상승시키며 영상을 획득하였다. 또한, angle에 의한 영상의 확대율을 확인하기 위해 본원에서 수술 전 검사 시 이용하는 측정 device 2개를 이용하여 동일한 방법으로 영상을 획득하였다. 결 과:기준이 되는 tube angle 0°의 영상과 15~30°까지 각각 tube angle을 5°씩 올려 획득한 영상을 비교해본 결과 tube angle 20° 영상이 pelvic bone과 spine의 모양, scotty dog’s sign의 모양 등에 있어 가장 근접했다. 하지만 25° 이상의 angle이 들어간 영상의 경우 기준 영상과 달리 큰 확대를 보였다. 결 론:본 연구에서 제시한 tube angle을 이용한 L-spine oblique 검사는 응급환자, 자세가 불가능한 환자, 검사 시 혹시 모를 2차적 손상의 가능성을 내포한 환자에게 있어 유용한 방법이다. 뿐만 아니라, fracture 유무의 관찰이 목적인 L-spine oblique의 검사 목적에도 적합하며 그 진단적 가치 또한 부족하지 않다. 특히 20° tube angle을 주어 검사하게 되면, 기존의 방법으로 얻은 영상과 유사한 oblique 영상을 얻을 수 있다. Purpose:Lumbar spine oblique is not so easy to make patients with spine injuries those who are suspected to have the damage take position for the examination. Also, it might strain the damaged spine during examination and could lead to deterioration of condition. Therefore, this study aims to obtain L-spine oblique image useful to diagnosis by using angle of tube and minimizing the posture change of patient. Materials and Methods:The abdomen phantom was conducted 40° oblique to obtain image. The examination condition was set as 80 kV, 32 mAs, 50 msec, 0° for tube angle, and SID (Source-to- Image-Distance) was vertically incised from 110cm to obtain image. As for the comparative image, SID was set as 100 cm, and rotated 90° for tube axis to increase 5° from 15~30° of detector to tube angle rather than conducting phantom oblique to obtain image. Also, in order to verify the magnification ratio of image by angle, 2 measuring devices used in the hospital for preoperative examination were utilized to change tube angle in same method to obtain image. Result:As for the result of comparison between 0° tube angle image which is the standard and images obtained by increasing 5° tube angle each from 15~30°, the 20° tube angle image was the closest one regarding the shape of pelvic bone, spine and scotty dog s sign. However, the images with 25° or larger angle showed larger magnification compared to standard image. Conclusion:L-spine oblique using tube angle proposed by this study is a useful examination method for emergency patients, patients who are unable to make poses, or patients who have potentials for second damage during examination. Furthermore, it fits the purpose of L-spine oblique examination which is to observe the condition of fracture, and its diagnostic value is sufficient. Especially, if the examination is conducted at 20° tube angle, oblique image similar to image obtained by previous method is available.

흡수식 냉동기의 증발기에 사용되는 전열촉진관에서 물의 유하 액막 증발 열전달에 대한 실험적 연구

박도현(Do-Hyun Park),한호승(Ho-Seung Han),김내현(Nae-Hyun Kim) 대한설비공학회 2019 설비공학 논문집 Vol.31 No.5

Thin film evaporation of water using enhanced tubes is one of the most common mode of heat transfer in absorption chillers evaporators. Proper design of the evaporators require adequate knowledge of evaporation heat transfer coefficient. In this study, seven enhanced tubes with different enhancement geometries were tested at a saturation temperature of 12℃, 15℃ tube-side water inlet temperature and a film flow rate of . The results indicated that the evaporation heat transfer coefficient of the Floral tube was lower than that of the smooth tube, while the Corrugated tube yielded almost the same heat transfer coefficient as the smooth tube. Notched Floral tube yielded a heat transfer coefficient of 72%, which is higher than that of smooth tube. It was found that Notched geometry was better than the End-cross geometry. Moreover, addition of Floral and Corrugated geometry formations to tubes having threedimensional protrusions, such as Notched or End-cross tubes further enhanced the evaporation heat transfer. As for the overall heat transfer coefficient, which accounts for both evaporation and tube-side heat transfer, End-cross Corrugated tube yielded the highest heat transfer coefficient at 57% as compared to smooth tube.

튜브 트레인 공력특성 해석

김태경(Tae-Kyung Kim),김규홍(Kyu-Hong Kim),권혁빈(Hyeok-Bin Kwon) 한국철도학회 2010 한국철도학회 학술발표대회논문집 Vol.2010 No.7

최근 한국에서는 세계적인 녹색기술을 맞아 향후 차세대 교통 시스템으로서 튜브 트레인 시스템의 본격적인 연구가 진행되고 있다. 한국 철도기술연구원(KRRI, Korea Railroad Research Institute)에서 튜브 트레인 시스템의 건설을 위한 목적으로 연구가 진행되고 있다. 본 논문에서는 기초연구의 일환으로 축대칭하며 긴 형상의 수송체가 가지는 다양한 튜브(터널) 내부의 압력, 막힘비율, 운행속도를 파라미터로 선정하여 전산해석을 수행하였다. 세부사항으로는 동일 형상의 운송체가 동일 운행속도를 가지고 일반적 압력의 개활지(오픈 시스템, 개활지 운행)를 운행할 때와, 다양한 환경(튜브 내 압력, 막힘비율, 운행속도)의 튜브 내부를 운행할 때에 대하여 튜브 트레인의 공력특성 연구를 수행하였다. 이를 통하여 다양한 운행속도-막힘비율 별로 개활지와 동일 에너지 효율 나오는 튜브 내 압력(P-D 관계)을 계산하였고, 막힘비율 증가에 따른 튜브 내 감압 정도(P-β 관계), 다양한 막힘비율-튜브 내 압력 별로 운행속도에 따른 전체 항력 양상(D-V 관계)을 보여 주었다. 그리고 개활지 운행시와 튜브 내부 운행시의 에너지 효율(주행저항)을 비교하였고, 튜브 내부 운행 시 트레인이 갖는 효율과 관계되는 충격파 발생의 임계속도(critical V-B 관계) 및 한계속도(V-P 관계)를 얻을 수 있었다. 이러한 연구의 결과는 튜브시스템 설계 및 건설에 꼭 필요한 것이며 가이드라인을 제시했다. Recently, full-scale research about a passenger tube train system is being progressed as a next-generation transportation system in Korea in light of global green technology. The Korea Railroad Research Institute (KRRI) has commenced official research on the construction of a tube train system. In this paper, we studied various parameters of the tube train system such as the internal tube pressure, blockage ratio, and operating speed through computational analysis with a symmetric and elongated vehicle. This study was about the aerodynamic characteristics of a tube train that operated under standard atmospheric pressure (open field system, viz., ground) and in various internal tube environments (varying internal tube pressure, blockage ratio, and operating speed) with the same shape and operating speed. Under these conditions, the internal tube pressure was calculated when the energy efficiency had the same value as that of the open field train depending on various combinations of the operating speed and blockage ratio (the P-D relation). In addition, the dependence of the relation between the internal tube pressure and the blockage ratio (the P-β relation) was shown. Besides, the dependence of the relation between the total drag and the operating speed depending on various combinations of the blockage ratio and internal tube pressure (the D-V relation) was shown. Also, we compared the total (aerodynamic) drag of a train in the open field with the total drag of a train inside a tube. Then, we calculated the limit speed of the tube train, i.e., the maximum speed, for various internal tube pressures (the V-P relation) and the critical speed that leads to shock waves under various blockage ratios, which is related to the efficiency of the tube train (the critical V-β relation). Those results provide guidelines for the initial design and construction of a tube train system.

Aerodynamic characteristics of a tube train

Kim, T.K.,Kim, K.H.,Kwon, H.B. Elsevier Scientific Pub. Co 2011 Journal of wind engineering and industrial aerodyn Vol.99 No.12

Recently, full-scale research about a passenger tube train system is being progressed as a next-generation transportation system in Korea in light of global green technology. The Korea Railroad Research Institute (KRRI) has commenced official research on the construction of a tube train system. In this paper, we studied various parameters of the tube train system such as the internal tube pressure, blockage ratio, and operating speed through computational analysis with a symmetric and elongated vehicle. This study was about the aerodynamic characteristics of a tube train that operated under standard atmospheric pressure (open field system, viz., ground) and in various internal tube environments (varying internal tube pressure, blockage ratio, and operating speed) with the same shape and operating speed. Under these conditions, the internal tube pressure was calculated when the energy efficiency had the same value as that of the open field train depending on various combinations of the operating speed and blockage ratio (the P-D relation). In addition, the dependence of the relation between the internal tube pressure and the blockage ratio (the P-β relation) was shown. Besides, the dependence of the relation between the total drag and the operating speed depending on various combinations of the blockage ratio and internal tube pressure (the D-V relation) was shown. Also, we compared the total (aerodynamic) drag of a train in the open field with the total drag of a train inside a tube. Then, we calculated the limit speed of the tube train, i.e., the maximum speed, for various internal tube pressures (the V-P relation) and the critical speed that leads to shock waves under various blockage ratios, which is related to the efficiency of the tube train (the critical V-β relation). Those results provide guidelines for the initial design and construction of a tube train system.

Design and synthesis of tube-in-tube structured NiO nanobelts with superior electrochemical properties for lithium-ion storage

Hwan Oh, Se,Park, Jin-Sung,Su Jo, Min,Kang, Yun Chan,Cho, Jung Sang Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.347 No.-

<P><B>Abstract</B></P> <P>Novel 1-D tube-in-tube structured NiO nanobelts were prepared by electrospinning process and subsequent one-step thermal treatment process. Nanobelt structured 1-D composite was electrospun from an aqueous solution containing poly(vinylpyrrolidone), citric acid, and dextrin which synergistically contributed to morphology control. The chemicals that optimized surface tension and viscosity of the aqueous solution enabled stable electrospinning process. Especially, dextrin played an important role in stable nanobelt formation due to its hygroscopic nature. During one-step oxidation process, the polymer composited nanobelt turned into carbon-free NiO@void@NiO tube-in-tube structured nanobelt by repeated combustion and contraction processes and Ostwald ripening mechanism. NiO tube-in-tube nanobelt prepared at 400 °C showed superior lithium-ion storage performances compared to those of NiO-C nanobelt and porous NiO nanobelt obtained at 300 and 500 °C, respectively. The discharge capacity of the tube-in-tube structured nanobelts after the 200th cycle at a current density of 1.0 A g<SUP>−1</SUP> was 992 mA h g<SUP>−1</SUP>. Also, high discharge capacity of 531 mA h g<SUP>−1</SUP> at a current density of 10.0 A g<SUP>−1</SUP> proved its excellent power density. High structural stability and morphological benefits of tube-in-tube nanobelts resulted in superior lithium storage performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel 1-D tube-in-tube structured NiO nanobelts were synthesized by electrospinning process. </LI> <LI> Influence of calcination temperature on the formation of nanobelts with various morphologies was investigated in detail. </LI> <LI> The chemicals that optimized surface tension and viscosity of the aqueous solution enabled stable electrospinning process. </LI> <LI> Unique structured NiO tube-in-tube nanobelts showed excellent lithium-ion storage performances. </LI> </UL> </P>

삼중관의 액압 성형성에 미치는 압력 경로의 영향

김상윤(Sang Yun Kim),주병돈(Byeong Don Joo),전찬후(Chan Hu Jeon),문영훈(Young Hoon) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11

Hydroforming is a technology that utilizes hydraulic pressure to form tube or sheet materials into desired shapes inside die cavities. Three-layered tube is assembled with inner, center and outer tube, similar in material or not and deforming simultaneously when internal pressure and axial feed were applied on the tube. Three-layered tube hydroforming is suitable to produce multiple tube joints which can be used in special applications such as automotive, aerospace, piping system and nuclear power plants. The precise control of internal pressure loading path in tube hydroforming process significantly affects on the final product quality. In this study, the effect of the loading path on forming characteristics in the tube hydroforming process is investigated. Free bulging tests were performed to study the expansion ability of the three tubes and tube hydroforming in a closed die was performed to investigate the hydroformability of the tubes. Hydroforming characteristics at various loading paths were analyzed and the loading path was optimized. The results show that final product of three-layered tube can be successfully fabricated by tube hydroforming process under optimized process parametes.

중공 성형품 제작을 위한 액압 성형 특성 분석

김상윤(S. Y. Kim),주병돈(B. D. Joo),전찬후(C. H. Jeon),한상욱(S. W. Han),문영훈(H. Y. Moon) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10

Tube hydroforming is the fabrication process that uses hydraulic pressure to form tube into desired shapes. Three layered tube is assembled with inner, center and outer tube, similar in material or not and deforming simultaneously when internal pressure and axial feed were applied on the tube. Compared with the conventional single-layered tube, triple tube has the merits of corrosion, conductivity, formability, strength, and abrasion resistance. In special working environments, multi-layered tubes with combined material properties, high strength and corrosion resistance are required to satisfy conflicting requirements. In this study, three layered tube hydroforming experiments was performed to fabricate hollow part. Free bulging tests were performed to study the expansion ability of the tubes. Also, free bulging characteristics of three-layered tube at various material combinations were analyzed and compared with results of the one tube and two-layered tube. The results show that hollow-part can be successfully fabricated by tube hydroforming process.