• Title/Summary/Keyword: Recompression

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Estimation of the Amount of Electric Power Saved in the Carbon Dioxide Liquefaction Process using LNG Cold Heat (LNG 냉열을 활용한 이산화탄소 액화공정에서 절감되는 전력량의 산출)

  • LEE, JIHWAN;CHO, JUNGHO
    • Journal of Hydrogen and New Energy
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    • v.31 no.2
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    • pp.259-264
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    • 2020
  • In this study, comparison study has been performed between two-stage compression and a vapor-recompression refrigeration cycle and a liquefaction using LNG cold heat. When using a first method using two-stage compression and a refrigeration cycle, at least three compressors are required, however when using LNG cold heat, no compressor is required since carbon dioxide can be pumped after condensing with the heat exchange with -160℃ of LNG. Through this study, we can save more than one hundred million KRW annually by using LNG cold heat instead of using gas compression and refrigeration cycle.

Application of Shock Generator to Supersonic Ejector Diffuser System (초음속 이젝터 디퓨져 시스템에서의 충격파 발생기 응용)

  • Lijo, Vincent;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.200-203
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    • 2011
  • Supersonic ejectors are simple mechanical components, which generally perform mixing and recompression of two fluid streams. Ejectors have found many applications in engineering. In aerospace engineering, they are used for high altitude testing (HAT) of a propulsion system by reducing the pressure of a test chamber. It is composed of three major sections: a vacuum test chamber, a propulsive nozzle, and a supersonic exhaust diffuser (SED). This paper aims at the improvement in HAT facility by focusing attention on the vertical firing rocket test stand with shock generators. Shock generators are mounted inside the SED for improving the pressure recovery. The results clearly showed that the performance of the ejector-diffuser system was improved with the addition of shock generators. The improvement comes in the form of reduction of the starting pressure ratio and the vertical height of test stand. It is also shown that shock generators are useful in reducing the total pressure loss in the SED.

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An Optimization Study on the Reliquefaction of Boil-Off Gas from Liquefied Petroleum Gas Storage Tank (액화석유가스 저장탱크로부터 발생하는 증발가스 재액화 공정의 최적화에 대한 연구)

  • NOH, SANGGYUN
    • Journal of Hydrogen and New Energy
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    • v.30 no.5
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    • pp.395-400
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    • 2019
  • Comparative studies between single- and two-stage refrigeration cycle using propane as a refrigerant have been performed for a vapor recompression refrigeration cycle. PRO/II with PROVISION release 10.2 from AVEVA company was used, and the Soave-Redlich-Kwong equation of state model with Twu's alpha function was selected for the modeling and optimization of the refrigeration cycle for the reliquefaction of BOG coming out from the LPG storage tank. In two-stage refrigeraton cycle, 24.8% of compressor power was reduced compared to that of single-stage refrigeration cycle through the optimization works.

A Study on the Price Evaluation Per 1 Ton of Liquefied Natural Gas According to the Refrigerants Supply Temperature in the Electric Refrigerator (전기식 냉동기에서 냉매의 공급온도에 따른 액화천연가스의 톤당 냉열 가격 산출에 대한 연구)

  • KIM, YONUNGWOO;PARK, ILSOO;CHO, JUNGHO
    • Journal of Hydrogen and New Energy
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    • v.30 no.5
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    • pp.473-477
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    • 2019
  • In this paper, cold heat price contained in the 1 ton/h of LNG has been evaluated using PRO/II with PROVISION release 10.2 from Aveva company when LNG is used to liquefy several refrigerants instead of using vapor recompression refrigeration cycle. Normal butane, R134a, NH3, R22, propane and propylene refrigerants were selected for the modeling of refrigeration cycle. It was concluded that LNG cold heat price was inversely proportional to the refrigerant supply temperature, even though LNG supply flow rate is not varied according to the refrigerant supply temperature.

A Computer Simulation Study on the Separation Process for Electronic Grade, Highly Pure Carbon Dioxide through a Cryogenic Distillation (심냉 증류를 통한 전자급 고순도 이산화탄소의 분리 공정에 대한 전산 모사 연구)

  • ILSU PARK;HUNGMAN MOON;JUNGHO CHO
    • Journal of Hydrogen and New Energy
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    • v.34 no.1
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    • pp.83-89
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    • 2023
  • In this study, a computer simulation work has been performed for the separation of electronic grade highly pure carbon dioxide more than 7 N purity through a cryogenic distillation process. For the cold utility as a cooling medium for a condenser of the cryogenic distillation column, propylene was utilized as a refrigerant in the vapor-recompression refrigeration cycle. Through this work, it was concluded that the cryogenic distillation column with two stage compression and refrigeration cycle were essential to obtain a highly-pure liquefied CO2.

Comparative Study on the Refrigeration Processes between Refrigeration Using Vapor Recompression and Refrigeration Using LN2 Cold Heat for the Carbon Dioxide Liquefaction (이산화탄소 액화를 위한 증기 재압축 냉동 공정과 액체질소 냉열을 이용한 냉동 공정의 비교 연구)

  • SANGGYUN NOH
    • Journal of Hydrogen and New Energy
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    • v.34 no.5
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    • pp.549-554
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    • 2023
  • In this paper, three kinds of studies have been completed to obtain highly purified carbon dioxide having more than 7N purity as an electronic grade quality. PRO/II with PROVISION release January 2023 from AVEVA company was used, and Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the cryogenic distillation process. When using LN2 cold heat, we can obtain highest recovery of carbon dioxide as a bottom product for a cryogenic distillation column.

Time-dependent behaviour of interactive marine and terrestrial deposit clay

  • Chen, Xiaoping;Luo, Qingzi;Zhou, Qiujuan
    • Geomechanics and Engineering
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    • v.7 no.3
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    • pp.279-295
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    • 2014
  • A series of one-dimensional consolidation tests and triaxial creep tests were performed on Nansha clays, which are interactive marine and terrestrial deposits, to investigate their time-dependent behaviour. Based on experimental observations of oedometer tests, normally consolidated soils exhibit larger secondary compression than overconsolidated soils; the secondary consolidation coefficient ($C_{\alpha}$) generally gets the maximum value as load approaches the preconsolidation pressure. The postsurcharge secondary consolidation coefficient ($C_{\alpha}$') is significantly less than $C_{\alpha}$. The observed secondary compression behaviour is consistent with the $C_{\alpha}/C_c$ concept, regardless of surcharging. The $C_{\alpha}/C_c$ ratio is a constant that is applicable to the recompression and compression ranges. Compared with the stage-loading test, the single-loading oedometer test can evaluate the entire process of secondary compression; $C_{\alpha}$ varies significantly with time and is larger than the $C_{\alpha}$ obtained from the stage-loading test. Based on experimental observations of triaxial creep tests, the creep for the drained state differs from the creep for the undrained state. The behaviour can be predicted by a characteristic relationship among axial strain rate, deviator stress level and time.

Numerical Investigation of the Effects of an Orifice Inlet on the Performance of an Ejector (Orifice Inlet효과에 의한 이젝터 성능에 관한 수치해석적 연구)

  • Lijo, Vincent;Kim, Heuy-Dong;Setoguchi, Toshiaki
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.318-322
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    • 2009
  • Supersonic ejectors are simple mechanical components, which generally perform mixing and/or recompression of two fluid streams. Ejectors have found many applications in engineering. In aerospace engineering, they are used for altitude testing of a propulsion system by reducing the pressure of a test chamber. It is composed of three major sections: a vacuum test chamber, a propulsive nozzle, and a supersonic exhaust diffuser. This paper aims at the improvement of ejector-diffuser performance by focusing attention on reducing exhaust back flow into the test chamber, since alteration of the backflow or recirculation pattern appears as one of the potential means of significantly improving low supersonic ejector-diffuser performance. The simplest backflow-reduction device was an orifice plate at the duct inlet, which would pass the jet and entrained fluid but impede the movement of fluid upstream along the wall. Results clearly showed that the performance of ejector-diffuser system was improved for certain a range of system pressure ratios, where as there was no appreciable transition in the performance for lower pressure ratios and the orifice plate was detrimental to the ejector performance for higher pressure ratios. It is found that an appropriately sized orifice system should produce considerable improvement in the ejector-diffuser performance in the intended range of pressure ratios.

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Numerical study of base flow of afterbodies for launch vehicle in supersonic turbulent flow (초음속 난류 유동장내의 발사체 후방 동체형상에 따른 기저유동의 수치적 계산)

  • Park Nam-Eun;Roh Hyung-Hun;Kim Jae-Soo
    • Journal of computational fluids engineering
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    • v.7 no.4
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    • pp.35-41
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    • 2002
  • The projectile afterbodies for zero-lift drag reduction has been analyzed using the Navier-Stokes equations with the κ-εturbidence model. The numerical method of a second order upwind scheme has been used on an unstructured adaptive grid system. Base drag reduction methods that have been found effective on axisymmetric bodies are boattailing, base bleed, base combustion, locked vortex afterbodies and multistep afterbodies. In this paper, turbulence flow and pressure charateristics have been studied for geometries of multistep afterbodies. The important geometrical and flow parameters relevant to the design of such afterbodies have been identified by step number, length and height. The flow over multistep aftoerbodies or base have many kinds of compressible flow characteristics including expansion waves at the trailing edge, recompression waves, separation and recirculating flow in the base region, shear flow and wake flow. The numerical results have been compared and analyzed with the experimental data. The flow characteristics have been clearly shown.

Study of the unsteady pressure oscillations induced by rectangular cavities in a supersonic flow field

  • Krishnan L.;Ramakrishna M.;Rajan S.C.
    • 한국전산유체공학회:학술대회논문집
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    • 2003.10a
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    • pp.294-298
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    • 2003
  • The complex, unsteady, self-sustained pressure oscillations induced by supersonic flow past a rectangular cavity is investigated using numerical simulations. The present numerical study is performed using a parallel, multiblock solver for the two-dimensional, compressible Navier­Stokes equations. Open cavities with length-to-depth (L / D) ratio in the range 0.5 - 3.3 are considered. This paper sheds light on the cavity physics, cavity oscillatory mechanism, and the organisation of vortical structures inside the cavity. The vortex shedding phenomenon, the shear layer impingement event at the aft wall and the movement of the acoustic/compression wave within the cavity are well predicted. The vortical structures· and the source of the acoustic disturbances are found to be located near the aft wall of the cavity. With the increase in the cavity length, strong recompression of the flow near the aft wall leading to a sudden jump in the cavity form drag is observed. The estimated cavity tones are in good agreement with the available semi­empirical relation. Multiple peaks are noticed in deep and long cavities. For the present free­stream Mach number 1.71, it is observed that around L/D=2.0, the cavity oscillatory mechanism changes from the transverse to longitudinal oscillatory mode. The effects of this transition on various fluid dynamics and acoustic properties are also discussed.

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