• 제목/요약/키워드: water saturation pressure

검색결과 157건 처리시간 0.021초

터보 냉동기용 핀 튜브에 관한 연구(II) - 비등 열전달에 관하여 - (A Study on Finned Tube Used in Turbo Refrigerator(II) - on boiling heat transfer -)

  • 한규일;김시영;조동현
    • 수산해양교육연구
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    • 제5권2호
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    • pp.119-127
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    • 1993
  • This work studies for heat transfer and pressure drop performance of integral inner and outer fin tubes, designed to enhance the heat transfer performance of smooth tubes for in recipro and turbo refrigerator or high performance compact heat exchangers. Eight different inner spiral fin copper tubes with integral fin at outside surfaces were employed to improve boiling heat transfer coeffcient. For comparison, tests were made using a plain tube having the inside diameter and an outside diameter equal to that at the root of the fins for the finned tubes. Pool boiling heat transfer is investigated experimentally and theoretically on single tube arrangement. The refrigerant evaporates at a saturation state of 1 bar on the outside tube surface heated by hot water. The refrigerant R11 ($CFCl_3$) was used at a pressure of $P_s=1bar$ as a convenient test fluid with a boiling temperature of $T_s=23.6^{\circ}C$. The observed heat transfer enhancement of boiling for finned tubes significantly exceeded that to be expected on grounds of increased area. The maximum Vapor - side enhancement(i.e., vapor - side heat transfer coefficient of finned tube/vapor - side coefficient for plain tube) was found to be around 4 at 1299fpm - 30grooves tube.

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신냉매용 자동차 에어콘 시스템에서의 건조기 설계에 관한 연구(온도감응식 팽창밸브의 개도에 따른) (Optimum Design Scheme of Receiver Dryer in an Automotive Air-Conditioning System using HFC-134a Refrigerant)

  • 송유호;김령훈;송영길
    • 한국자동차공학회논문집
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    • 제4권6호
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    • pp.187-195
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    • 1996
  • Because an alternative refrigerant(HFC-134a) is being used instead of CFC-12 for automotive air-conditioning system, newly designed air-conditioning components are necessary due to changes in characteristics. Optimum design scheme for receiver dryer in an automotive air-conditioning system is described with emphases upon the volume of desiccant and container. The volume of the container, that is manufactured based on the study, is reduced down to one half of the existing receiver dryers.

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퇴적층에서의 가스 하이드레이트 생성 특성 (Formation characteristics of gas hydrate in sediments)

  • 이재형;이원석;김세준;김현태;허대기
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2005년도 춘계학술대회
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    • pp.630-633
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    • 2005
  • Some gases can be formed into hydrate by physical combination with water under appropriate temperature and pressure condition. Besides them, it was found that the pore size of the sediments can affect the formation and dissociation of hydrate. In this study, formation temperatures of carbon dioxide and methane hydrate have been measured using isobaric method to investigate the effects of flow rates of gases on formation condition of hydrate in porous rock samples. The flow rates of gases were controlled using a mass flow controller. To minimize Memory effect, system temperature increased for the dissociation of gas hydrates and re-established the initial saturation. The results show that the formation temperature of hydrate decreases with increasing the injection flow rate of gas. This indicates that the velocity of gas in porous media may act as kinds of inhibitor for the formation of hydrate.

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강우시 사면안전율 변화를 이용한 열차운전규제기준 개발 (The Development of Rail-Transport Operation Control using the Variation of Slope Stability under Rainfall)

  • 김현기;이진욱;신민호
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2003년도 추계학술대회 논문집(II)
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    • pp.397-402
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    • 2003
  • Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment are defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall infiltration show that rainfall infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.

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Preliminary Simulation Analysis of the Large Scale Gas Injection Test (LASGIT) Experiment Using the OpenGeoSys (OGS) model

  • Park, Chan-Hee
    • 한국지구과학회지
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    • 제33권5호
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    • pp.401-407
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    • 2012
  • The OGS model is configured and used for simulation of the LASGIT project. The modeling conditions and the simulation results from the previous work by Walsh and Calder (2009) are analyzed to see if the simulation configuration is done correctly and to apply for the LASGIT project. Except for the unrealistic modeling conditions used previously, the simulation results successfully demonstrated helium propagation that is typical for the two-phase flow. The results indicated that the relations of capillary pressure and the relative permeability against water saturation used previously should be updated. An elaborated simulation with more realistic parameters should be used to improve the weak points of preliminary work.

암모니아의 수평관내 단상 및 응축 열전달계수의 측정 (Measurement of Single Phase and Condensation Heat Transfer Coefficients of Ammonia in a Horizontal Tube)

  • 백영진;장영수;김영일
    • 설비공학논문집
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    • 제12권6호
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    • pp.561-569
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    • 2000
  • Single phase and condensation heat transfer characteristics of ammonia in a horizontal tube have been investigated experimentally The horizontal test section is composed of smooth SUS316 tube for refrigerant flow, surrounding annulus for water flow, and temperature and Pressure measuring sensors. For single phase test, subcooled ammonia mass flux was varied from 320 to 501 kg/mrs and temperature was varied from 18 to $47^{\circ}C$. For condensation test, mass flux and saturation temperature were varied from 86 to 128 kg/$m^2$s and 34 to $47^{\circ}C$, respectively. The equations of Gnielinski Soliman et al., Traviss et at., Cavallini and Zecchin, Shah, Chen et al., Tandon et al., and Chilli and Anand were compared with the experimental data. New correlations are proposed based on the experimental results and the absolute mean deviation of the experimental data becomes 1.0% for single phase test and 4.9% for condensation test.

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프로판-이소부탄 혼합냉매를 적용한 소형 냉동시스템의 성능 특성에 관한 연구 (Performance Characteristics of Propane/isobutane Mixtures in a Small Refrigeration System)

  • 윤원재;김용찬
    • 설비공학논문집
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    • 제14권1호
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    • pp.73-82
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    • 2002
  • A small refrigeration system used in a water purifier was tested by employing propane/isobutane (R-290/R-6OOa) mixtures as an alternative refrigerant of R-12. The drop-in tests were performed by varying mass fraction of propane at 0.25, 0.5 and 0.75 with a change of both refrigerant charge amount and capillary tube length in order to find an optimum composition in aspect of performance and reliability of the system. As a result, the mixture of 50% propane-50% isobutane showed the best performance and reliability among them in a small refrigeration system. During steady state operations, both the COP and refrigeration capacity increased by 4% and 9%, respectively, as compared to the baseline R-12 system. In addition, the propane/isobutane (50/50) mixture system yielded advantages in the minimization of modification and redesigning of system components due to very similar saturation tempera- ture and pressure characteristics with R-12.

A simplified method to estimate the total cohesion of unsaturated soil using an UC test

  • Lin, Horn-Da;Wang, Chien-Chih;Wang, Xu-Hui
    • Geomechanics and Engineering
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    • 제16권6호
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    • pp.599-608
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    • 2018
  • This study investigates the feasibility of adopting the results of the UC (unconfined compression) test to assess the total cohesion of the unsaturated soil. A series of laboratory tests were conducted on samples of unsaturated lateritic soils of northern Taiwan. Specifically, the unconfined compression test was combined with the pressure plate test to obtain the unconfined compression strength and its matric suction of the samples. Soil samples were first compacted at designated water content and then subjected to the wetting process for saturation and the subsequent drying process to its target suction using the apparatus developed by the authors. The correlations among the matric suction, the unconfined compression strength and the total cohesion were studied. As a result, a simplified method to estimate the total cohesion using the unconfined compressive strength is suggested. The calculated results compare reasonably with the unsaturated triaxial test results. Current results show good performance; however, further study is warranted.

A semi-analytical solution to spherical cavity expansion in unsaturated soils

  • Tang, Jianhua;Wang, Hui;Li, Jingpei
    • Geomechanics and Engineering
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    • 제25권4호
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    • pp.283-294
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    • 2021
  • This paper presents a rigorous solution for spherical cavity expansion in unsaturated soils under constant suction condition. The hydraulic behavior that describes the saturation-suction relationship is modeled by a void ratio-dependent soil-water characteristic curve, which allows the hydraulic behavior to fully couple with the mechanical behavior that is described by an extended critical state soil model for unsaturated soil through the specific volume. Considering the boundary condition and introducing an auxiliary coordinate, the problem is formulated to a system of first-order differential equations with three principal stress components and suction as basic unknowns, which is solved as an initial value problem. Parameter analyses are conducted to investigate the effects of suction and the overconsolidation ratio on the overall expansion responses, including the pressure-expansion response, the distribution of the stress components around the cavity, and the stress path of the soil during cavity expansion. The results reveal that the expansion pressures and the distribution of the stress components in unsaturated soils are generally higher than those in saturated soils due to the existence of suction.

Study on dryout heat flux of axial stratified debris bed under top-flooding

  • Wenbin Zou;Lili Tong;Xuewu Cao
    • Nuclear Engineering and Technology
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    • 제56권2호
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    • pp.636-643
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    • 2024
  • The coolability of the debris bed with a simulant of solidified corium is experimentally studied, focusing on the effects of the structure of the axial stratified debris bed on the dryout heat flux (DHF). DHF was obtained for the four structures with different particle sizes for the axial stratified debris bed under top flooding. The experimental results show that the dryout position of the axial stratified debris bed is formed at the stratified interface indicated by the temperature rise, and the DHF of the axial stratified bed is much lower than that of the homogeneous bed packed with the upper small particles. To predict the dryout heat flux of the stratified debris beds, by considering the properties of the mixed area, a one-dimensional dryout heat flux model of the porous medium is derived from a water and vapor momentum equation for porous medium, two-phase permeability modifications, interfacial drag, and the correlation between capillary pressure and liquid saturation and verified with the experimental data. The modified model can give reasonable results under different structures.