• Title/Summary/Keyword: Thermal analysis characteristics

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Comparison of Active and Passive Sampler for Determining Temperal and Spatial Concentration Assessment of the Main Volatile Organic Compounds Concentration in Shihwa Industrial Complex (시화산업단지에서 주요 휘발성유기물질의 시간적, 공간적 농도 파악을 위한 능동식과 수동식 시료채취기 비교)

  • Byeon, Sang-Hoon;Choi, Hyeon-Il;Moon, Hyung-Il;Lee, Jung-Geun;Kim, Jung-Keun
    • Journal of Korean Society of Environmental Engineers
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    • v.33 no.11
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    • pp.790-796
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    • 2011
  • In this study, we measured the concentrations of volatile organic compounds (VOCs) in Shiwha area by using active and passive sampler. We did a comparative analysis of the characteristics of the active sampler and passive sampler. In the case of the passive sampler, the average TVOC concentration of the industrial area was 1.86 times higher than that of the residential area. In the case of the active sampler, the average TVOC concentration of the industrial area was 1.07 times higher than that of the residential area. When using the passive sampler, the concentration of VOCs in the industrial area was noted to be higher than the concentration found in the residential area. However, when we used the thermal desorption tube, the concentration of residential area was higher rather than that of industrial area in some substances such as trichloroethylene, toluene, ethylbenzene, and xylene. Toluene was a larger percentage of the overall BTEX ratio. In case of the passive sampler, the relative ratio of toluene, ethylbenzene, and xylene was higher in the industrial area than in the residential area. In contrast in case of the thermal desorption tube, the ratio of these substances was higher in the residential area rather than in the industrial area. The passive sampling in this study showed an appropriate method to analyze the temporal and spatial concentrations of air contaminants. This assessment would prove to be useful for its observance of standards or epidemical study.

Simulation of High-current Vacuum Arcs: (I)Axial Magnetic Field (진공차단부 대전류 아크 해석: (I)축방향 자기장)

  • Hwang, Jung-Hoon;Lee, Jong-Chul;Choi, Myung-Jun;Kwon, Jung-Lock;Kim, Youn-Jea
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2500-2505
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    • 2007
  • The vacuum interrupter (VI) is used for medium-voltage switching circuits due to its abilities and advantages as a compact and environmental friendly circuit breaker. In general, the application of a sufficiently strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. A full understanding of the vacuum arc physics is very important since it can aid to improve the performance of vacuum interrupter. In order to closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, we have investigated the electromagnetic behaviors of high-current vacuum arcs for two different types of AMF contacts, which are coil-type and cup-type, using a commercial finite element analysis (FEA) package, ANSYS. The present results are compared with those of MAXWELL 3D, a reliable electromagnetic analysis software, for verification.

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Numerical Analysis of Flow Distribution in the Scaled-down APR+ Using Two-Equation Turbulence Models (2방정식 난류모델을 이용한 축소 APR+ 내부 유동분포 수치해석)

  • Lee, Gong Hee;Bang, Young Seok;Cheong, Ae Ju
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.4
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    • pp.220-227
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    • 2015
  • Complex thermal hydraulic characteristics exist inside the reactor because the reactor internals consist of fuel assembly, internal structures and so on. In this study, to examine the effect of Reynolds-Averaged Navier-Stokes (RANS)-based two-equation turbulence models in the analysis of flow distribution inside a 1/5 scaled-down APR+, simulation was performed using the commercial computational fluid dynamics software, ANSYS CFX R.13 and the predicted results were compared with the measured data. It was concluded that reactor internal flow pattern was locally different depending on the turbulence models. In addition, the prediction accuracy of k-${\varepsilon}$ model was superior to that of other two-equation turbulence models and this model predicted the relatively uniform distribution of core inlet flow rate.

Characteristics of Thermodynamic Performance of Heat Exchanger in Organic Rankine Cycle Depending on Pinch Temperature Difference (유기랭킨사이클에서 핀치온도차의 변화에 따른 열교환기의 열역학적 성능특성)

  • KIM, KYOUNG HOON;JUNG, YOUNG GUAN;PARK, SANG HEE
    • Journal of Hydrogen and New Energy
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    • v.26 no.6
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    • pp.590-599
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    • 2015
  • In this paper a performance analysis is carried out based on the first and second laws of thermodynamics for heat exchanger in organic Rankine cycle (ORC) for the recovery of low-temperature finite thermal energy source. In the analysis, effects of the selection of working fluid and pinch temperature difference are investigated on the performance of the heat exchanger including the effectiveness of the heat exchanger, exergy destruction, second-law efficiency, number of transfer unit (NTU), and pinch point. The temperature distribution are shown depending on the working fluids and the pinch temperature difference. The results show that the performance of the heat exchanger depends on the pinch temperature difference sensitively. As the pinch temperature increases, the exergy destruction in the evaporator increases but the effectiveness, second law efficiency and NTU decreases.

Analysis of a Cryogenic Nitrogen-Ambient Air Heat Exchanger Including Frost Formation (착상을 고려한 극저온 질소-대기 열교환기의 해석)

  • 최권일;장호명
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.9
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    • pp.825-834
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    • 2000
  • A heat exchanger analysis is performed to investigate the heating characteristics of cryogenic nitrogen by ambient air for the purpose of cryogenic automotive propulsion. The heat exchanger is a concentric triple-passage for supercritical nitrogen, and the radial fins are attached on the outermost tube for the crossflow of ambient air. The temperature distribution is calculated for the nitrogen along the passage, including the real gas properties of nitrogen, the fluid convections and the conductions through the tube walls and the fins. Since the wall temperature of the outer (ambient side) tube is very low in most cases, a heavy frost can be formed on the surface, affecting the heat exchange performance. By the method of the similarity between the heat and the mass transfer of moist air, the frost growth and the time-dependent effectiveness of the heat exchanger are calculated for various operating conditions. It is concluded that the frost formation can augment the heating of nitrogen during the initial period because of the latent heat, then gradually degrades the heat exchange because of the increased thermal resistance. Practical design issues are discussed for the flow rate of nitrogen, the velocity and humidity of ambient air, and the sizes of the fin.

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The Development of KOGAS Membrane for LNG Storage Tank (LNG 저장탱크용 KOGAS 멤브레인 개발)

  • Oh, Byoung-Taek;Kim, Young-Kyun;Yoon, Ihn-Soo;Seo, Heung-Seok;Hong, Seong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.6
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    • pp.1203-1208
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    • 2002
  • LNG demand has been rapidly increasing in Korea for a variety of reasons including stable supply, non-polluting, and high combustion efficiency characteristics. As a result the construction and expansion of LNG storage facilities have been continuing at a vigorous pace. Korea Gas Corp. (KOGAS) has developed the design technology of the LNG storage tank. One of the most important structural core element of the LNG storage tank is the membrane, made by stainless steel. The membrane to be applied inside of LNG storage tank is provided with corrugations to absorb thermal contraction and expansion caused by LNG temperature. Analytical results have been performed to investigate the strength of the membrane and the reaction farce at the anchor point. Experimental studies are performed to investigate the deformation and strength of the membrane which is designed by Kogas. All experiments are conducted on the basis of RPIS, and we found the results are fully satisfied with the RPIS.

Stress Analysis of Pipe Connection Process Using Clamping Ring (구속 링을 이용한 관 결합 공정의 응력해석)

  • Yang, Young-Soo;Bae, Kang-Yul
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.16 no.2
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    • pp.81-87
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    • 2017
  • The pipe connection process using a clamping ring is used for joining small pipes in the refrigerator and air-conditioner industries instead of the brazing process, which induces inevitable thermal deformation in the pipes. However, few studies have been carried out on the process to select optimal parameters in joining pipes, and studies on the relation between the process parameters of the connection and connecting force of the joint have not been conducted. In this study, the connection process of pipes with the clamping ring was modeled using the finite element method (FEM) and analyzed to obtain the contact stress distribution between the pipes with which the connecting force of the joint was estimated. Considering the characteristics of pipe connection, the process was modeled and simulated in a two-dimensional axisymmetric solution domain. With the numerical model, the effect of ring shape on the connection was studied by adding a projection to the end of a ring or changing the length of a ring. The results of the analyses revealed that the contact stress distribution could be predicted with the suggested model. The effect of the ring shape was also presented. The effect of any combination of process parameters could be easily estimated through the related analyses.

Continuous Measurements of Aromatic VOCs in a Mid-eastern Region of Seoul during Winter 2002/2003 (방향족 휘발성 유기화합물의 겨울철 연속 관측 연구)

  • 최여진;오상인;김기현
    • Journal of Korean Society for Atmospheric Environment
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    • v.19 no.5
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    • pp.491-502
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    • 2003
  • In the present work, the distribution characteristics of ambient volatile organic compounds (VOCs) were investigated at high temporal resolution from a monitoring station located in a mid-eastern area of Seoul. A total number of 587 samples were collected during December 2002 to January 2003. The measurements of VOC were conducted by a combination of on-line air sampling and thermal desorption unit (TDU) coupled with capillary GC/FID analysis. A total of five aromatic compounds (BTEX: benzene, toluene, ethylbenzene, m, p-xylene, and o-xylene) were measured routinely at hourly intervals during the whole study period. The mean concentrations of BTEX measured in our study period were found in the order: toluene (8.99 $\pm$5.38 ppb) > benzene (0.92$\pm$0.52 ppb) > m, p-xylene (0.51$\pm$0.34 ppb) > 0- xylene (0.48$\pm$0.35 ppb) > ethyl benzene (0.43$\pm$ 0.32 ppb). The BTEX concentrations were generally higher during the daytime than the nighttime, exhibiting certain patterns on a weekly basis. Results of our analysis indicate that the unusually high concentrations of toluene, while showing good correlations with other VOCs, can be a good indicator of air pollution in the study area.

A Study on Thermal Characteristics of Stratospheric Airship Considering Radiation Heat Transfer (복사 열전달에 의한 성층권 무인 비행선의 열 특성 연구)

  • Kim Seung-Min;Lee Sang-Myeong;Roh Tae-Seong;Choi Dong-Hwan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.285-288
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    • 2005
  • A Stratospheric airship should stay long to achieve its original mission. Meanwhile, to obtain what the solar radiation and heat transfer have an effect on Stratospheric condition, heat analysis has been done. For this work, Stratospheric heat condition's been examined and for the numerical analysis, by using Gridgen, grids of airship have been generated. And by using STAR-CD, the study about heat characteristic of airship model was carried out. Especially, with changing the position of the Sun, the temperature change of the airship body was focused on. With this background, the possibility of realizing the simulation of the effects solar radiation have on the Stratospheric airship.

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Fundamental Study on Heat Transfer Enhancement Effect of Microscale Surface Wrinkles (마이크로 표면주름 형상에 따른 열전달 촉진효과 기초연구)

  • Park, Hee-Jin;Park, Sang-Hu
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.9
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    • pp.447-452
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    • 2014
  • We evaluated heat transfer characteristics of microscale wrinkles using a CFD (computational fluid dynamics) analysis. In order to verify the heat transfer effect of wrinkles having various shapes, we introduce wrinkling processes to generate few different shapes of wrinkles such as macroscale ($200{\sim}400{\mu}m$ width), microscale ($10{\sim}30{\mu}m$ width), and hierarchical (microscale on macroscale wrinkle) wrinkles, using repetitive-dividing-volume (RDV) method for single-shape of wrinkles and connected method of UV-weakly polymerization with thermal curing for hierarchical structure of winkles. The analysis results of simplified CFD model showed that heat flux on heated plate was changed by the shape of wrinkles on the plate. The increase in heat flux of about 2.6 times was achieved in the case where hierarchical wrinkle structure was used.