• Title/Summary/Keyword: R2-loop

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Evaporation Heat Transfer Characteristics of $CO_2$ in a Horizontal Tube

  • Lee Dong-Geon;Son Chang-Hyo;Oh Hoo-Kyu
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.3
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    • pp.297-305
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    • 2005
  • The evaporation heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter. a pre-heater and evaporator (test section). The test section consists of a smooth. horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500\;kg/m^{2}s$. saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$. and heat flux of 10 to $40\;kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has greatly effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality. heat flux and saturation temperature. The evaporation heat transfer coefficient of $CO_2$ is very larger than that of R-22 and R-134a. In making a comparison between test results and existing correlations. the present experimental data are the best fit for the correlation of Jung et al. But it was failed to predict the evaporation heat transfer coefficient of $CO_2$ using by the existing correlation. Therefore. it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

Evaporation Heat Transfer Characteristics of $CO_2$ in a Horizontal Tube

  • Son Chang-Hyo;Kim Dae-Hui;Choi Sun-Muk;Kim Young-Ryul;Oh Hoo-Kyu
    • International Journal of Air-Conditioning and Refrigeration
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    • v.13 no.4
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    • pp.167-174
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    • 2005
  • The evaporation heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500kg/m^2s$, saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$, and heat flux of 10 to $40kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has greater effect on nucleate boiling than convective boiling. The evaporation heat transfer coefficient of $CO_2$ is highly dependent on the vapor quality, heat flux and saturation temperature. The evaporation heat transfer coefficient of $CO_2$ is very larger than that of R-22 and R-134a. In comparison with test results and existing correlations, the best fit of the present experimental data is obtained with the correlation of Jung et al. But the existing correlations failed to predict the evaporation heat transfer coefficient of $CO_2$. Therefore, it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

Major B-H Loop Measurement of Toroidal Shape Magnetic Powder Core (토로이드형 분말코어의 Major B-H Loop 측정)

  • Son, Derac
    • Journal of the Korean Magnetics Society
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    • v.24 no.3
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    • pp.76-80
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    • 2014
  • Toroidal cores made of metallic powder requires large magnetic field strength up to few decade kA/m to obtain major hysteresis loop. To overcome thermal heat generation problem from large exciting current during measurement, we have employed a real time hysteresis loop tracer which can digitize and calculate B-H signals in personal computer as real time. For example, when we magnetize specimen at 10 Hz frequency, we could display hysteresis loops 10 times per second. Using the real time hysteresis loop tracer, we could measure major hysteresis loop of toroidal shape metallic powder core at maximum flux density or maximum magnetic field strength to be measured within 5 second not to significant increasement of specimen temperature due to the heat dissipation from coil windings. For the constructed hysteresis loop tracer, we could measure hysteresis loop at magnetic field strength higher than 50 kA/m for the toroidal shape specimen.

Detection of Cleavage Sites on 5S rRNA by Methidiumpropyl-EDTA-Iron(II)

  • Kim, Sang-Bumn;Cho, Bong-Rae;Lee, Young-Hoon;Park, In-Won
    • BMB Reports
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    • v.29 no.2
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    • pp.133-136
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    • 1996
  • The affinity cleavage reagent Methidiumpropyl-EDTA-Iron(II) is applied to the structural analysis of 5S rRNA. Analysis of cleavage sites induced by MPE-Fe(II) on 5S rRNA shows that MPE intercalates easily between the unstable base pairs or into the bulges, thereby it strongly cuts the nucleosides nearby. The stable helical stems A, B, D and E as well as loop d are weakly cut. Most of the single-stranded loops are not cleaved. Based on the cleavage pattern of the 5S rRNA by MPE-Fe(II) and RNase V1, we suggest that MPE-Fe(II) may be used as a potential chemical probe in searching for the unstable helical regions of RNA, and for the sequences that appear to be involved in folding and distorting 5S rRNA.

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Design of Loop Type Inserting Slot Antenna to Apply Bluetooth/Zigbee/WiMax/WLAN(2.4~5.82 GHz) Band (Bluetooth/Zigbee/WiMAX/WLAN(2.4~5.82 GHz) 대역 응용을 위해 루프 형태를 삽입한 슬롯 안테나 설계)

  • Hong, Yoon-Gi;An, Sang-Chul;Jung, Hoon;Hong, Won-Gi;Jung, Cheon-Seok
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.5
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    • pp.435-443
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    • 2009
  • In this paper, we propose a microstrip slot antenna that works in Bluetooth, Zigbee, WiMAX and WLAN frequency bands($2.4{\sim}5.825\;GHz$). To get the wide bandwidth from the microstrip antenna proposed, we insert a pair of parastic strips along the feed line on the FR-4 dielectric substance(${\varepsilon}_r=4.8$). Furthermore, a simple geometrical rotation with quadrilateral slot is designed to maximize the bandwidth and to gain a wider frequency band than the conventional rectangular slot antenna. A additional design of the loop type is added to a cactus-shaped patched for 2.4 GHz ISM frequency band. The total measured bandwidth of the antenna is from 2.4 GHz to 6 GHz and the maximum gains of the antenna are 3.82 dBi, 4.48 dBi, 6.41 dBi and 6.65 dBi at the frequencies of 2.4 GHz, 3.5 GHz, 5.25 GHz and 5.77 GHz.

Development and Performance Verification of Real-time Hybrid Navigation System for Autonomous Underwater Vehicles

  • Kim, Hyun Ki;Jung, Woo Chae;Kim, Jeong Won;Nam, Chang Woo
    • Journal of Positioning, Navigation, and Timing
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    • v.5 no.2
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    • pp.97-107
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    • 2016
  • Military Autonomous Underwater Vehicle (AUV) is utilized to search a mine under the sea. This paper presents design and performance verification of real-time hybrid navigation system for AUV. The navigation system uses Doppler Velocity Log (DVL) integration method to correct INS error in underwater. When the AUV is floated on the water, the accumulated error of navigation algorithm is corrected using position/velocity of GPS. The navigation algorithm is verified using 6 Degree Of Freedom (DOF) simulation, Program In the Loop Simulation (PILS). Finally, the experiments are performed in real sea environment to prove the reliability of real-time hybrid navigation algorithm.

Simulation of the Effect of EGR Configuration on EGR Rate in a Passenger Diesel Engine with Two-Stage Turbocharger (2단 터보과급기 장착 승용디젤엔진에서 EGR 배열 방식이 EGR율에 미치는 영향에 대한 시뮬레이션)

  • Chung, Jin-Eun;Roh, Ho-Jong;Chung, Jae-Woo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.11
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    • pp.4137-4144
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    • 2010
  • In this study, the simulations were carried out to show the effect of the EGR configuration in a passenger diesel engine with 2-stage turbocharger on the EGR rate. The AMESim and IFP Engine Library were used to make the program for the simulation. Three EGR configurations, HPL(high pressure loop), LPL(low pressure loop), and SLPL(semi low pressure loop), were considered. The EGR rate in the HPL and LPL EGR routes were 6.4% and 10.0% respectively but the rate in SLPL route was 18.0% and their air/fuel ratio for all three cases was 21. Therefore the SLPL EGR configuration may be positively considered in the design of the passenger diesel engine with 2-stage turbocharger.

Effect of Air Gap Thickness on Top Heat Loss of a Closed-loop Oscillating Heat Pipe Solar Collector

  • Nguyen, Kim-Bao;Choi, Soon-Ho;Yoon, Doo-Ho;Choi, Jae-Hyuk;Oh, Cheol;Yoon, Seok-Hun
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.7
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    • pp.994-1002
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    • 2009
  • In this paper, effect of air gap thickness between absorber plate and glass cover on top heat loss of a closed loop oscillating heat pipe (CLOHP) solar collector was investigated. The CLOHP, which is made of copper with outer diameter of 3.2mm and inner diameter of 2.0mm, comprises 8 turns with heating, adiabatic and cooling section. The heating section of the heat pipe was attached to absorber plate which heated by solar simulator simulated by halogen lamps. The cooling section of the heat pipe was inserted into collector's cooling section that made of transparent acrylic. Temperatures of absorber plate, glass cover, and ambient air measured by K-type thermocouple and were recorded by MV2000-Yokogawa recorder. Top heat loss coefficients and top heat loss of the collector corresponding to some cases of air gap thickness were determined. The result of experiment shows the optimal air gap thickness for minimum top heat loss of this solar collector.

Evaluation of 3D printability of cementitious materials according to thixotropy behavior

  • Lee, Keon-Woo;Choi, Myoung Sung
    • Advances in concrete construction
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    • v.11 no.2
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    • pp.141-149
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    • 2021
  • This study is a basic research for evaluating the buildability of cementitious materials for three-dimensional (3D) printing. In the cement paste step, the thixotropy behavior according to the resting time, which represents the time interval between each layer, was analyzed. In addition, the relationship between the thixotropy behavior and 3D concrete printing buildability was derived by proposing a measurement method that simulates the 3D concrete printing buildup process. The analysis of the tendency of the thixotropy behavior according to the resting time revealed that the area of the hysteresis loop (AHyst) showed a tendency to increase and then converge as the resting time increased, which means hysteresis loop approach critical resting time for sufficient buildability. In the thixotropy behavior analysis that simulates the 3D concrete printing buildup process, the buildup ratio, which is the recovery rate of the shear stress, showed a tendency to increase and then converge as the resting time increased, which are similar results like hysteresis loop. It was concluded that AHyst and the buildup ratio can be used as parameters for determining the resting time, and they have close relationships with 3D concrete printing buildability.

Rapid and Efficient Detection of 16SrI Group Areca Palm Yellow Leaf Phytoplasma in China by Loop-Mediated Isothermal Amplification

  • Yu, Shao-shuai;Che, Hai-yan;Wang, Sheng-jie;Lin, Cai-li;Lin, Ming-xing;Song, Wei-wei;Tang, Qing-hua;Yan, Wei;Qin, Wei-quan
    • The Plant Pathology Journal
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    • v.36 no.5
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    • pp.459-467
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    • 2020
  • Areca palm yellow leaf (AYL) disease caused by the 16SrI group phytoplasma is a serious threat to the development of the Areca palm industry in China. The 16S rRNA gene sequence was utilized to establish a rapid and efficient detection system efficient for the 16SrI-B subgroup AYL phytoplasma in China by loop-mediated isothermal amplification (LAMP). The results showed that two sets of LAMP detection primers, 16SrDNA-2 and 16SrDNA-3, were efficient for 16SrI-B subgroup AYL phytoplasma in China, with positive results appearing under reaction conditions of 64℃ for 40 min. The lowest detection limit for the two LAMP detection assays was the same at 200 ag/μl, namely approximately 53 copies/μl of the target fragments. Phytoplasma was detected in all AYL disease samples from Baoting, Tunchang, and Wanning counties in Hainan province using the two sets of LAMP primers 16SrDNA-2 and 16SrDNA-3, whereas no phytoplasma was detected in the negative control. The LAMP method established in this study with comparatively high sensitivity and stability, provides reliable results that could be visually detected, making it suitable for application and research in rapid diagnosis of AYL disease, detection of seedlings with the pathogen and breeding of disease-resistant Areca palm varieties.