• 제목/요약/키워드: Pre-cooler

검색결과 28건 처리시간 0.013초

Effectiveness analysis of pre-cooling methods on hydrogen liquefaction process

  • Yang, Yejun;Park, Taejin;Kwon, Dohoon;Jin, Lingxue;Jeong, Sangkwon
    • 한국초전도ㆍ저온공학회논문지
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    • 제22권3호
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    • pp.20-24
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    • 2020
  • The purpose of this analytic study is to design and examine an efficient hydrogen liquefaction cycle by using a pre-cooler. The liquefaction cycle is primarily comprised of a pre-cooler and a refrigerator. The fed hydrogen gas is cooled down from ambient temperature (300 K) to the pre-cooling coolant temperature (either 77 K or 120 K approximately) through the pre-cooler. There are two pre-cooling methods: a single pre-coolant pre-cooler and a cascade pre-cooler which uses two levels of pre-coolants. After heat exchanging with the pre-cooler, the hydrogen gas is further cooled and finally liquefied through the refrigerator. The working fluids of the potential pre-cooling cycle are selected as liquid nitrogen and liquefied natural gas. A commercial software Aspen HYSYS is utilized to perform the numerical simulation of the proposed liquefaction cycle. Efficiency is compared with respect to the various conditions of the heat exchanging part of the pre-cooler. The analysis results show that the cascade method is more efficient, and the heat exchanging part of the pre-coolers should have specific UA ratios to maximize both spatial and energy efficiencies. This paper presents the quantitative performance of the pre-cooler in the hydrogen liquefaction cycle in detail, which shall be useful for designing an energy-efficient liquefaction system.

수소충전소용 프리쿨러를 위한 수소가스 냉각에 관한 연구 (Study on Cooling of Hydrogen Gas for the Pre-Cooler in the Hydrogen Refueling Station)

  • 이경한;구경모;유철휘;황갑진
    • 한국수소및신에너지학회논문집
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    • 제30권3호
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    • pp.237-242
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    • 2019
  • In the hydrogen refueling station (HRS), it is need the pre-cooling system (PCS) to limit the inside temperature ($85^{\circ}C$) of the onboard thank (700 bar) and to charge the hydrogen at short time (within 3 minutes) to fuel cell electric vehicle (FCEV). From those safety reasons, the temperature of hydrogen gas must be controled $-33^{\circ}C$ to $-40^{\circ}C$ in PCS. The cooling test of the gaseous ($N_2$, He, $H_2$) was carried out using heat exchanger (pre-cooler) by indirect cooling and direct cooling method. It was confirmed that the temperature of hydrogen gas had below $-40^{\circ}C$ at below $-75^{\circ}C$ of chiller temperature in direct cooling.

Prediction model of 4.5 K sorption cooler for integrating with adiabatic demagnetization refrigerator (ADR)

  • Kwon, Dohoon;Kim, Jinwook;Jeong, Sangkwon
    • 한국초전도ㆍ저온공학회논문지
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    • 제24권1호
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    • pp.23-28
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    • 2022
  • A sorption cooler, which utilizes helium-4 as a working fluid, was previously developed and tested in KAIST. The cooler consists of a sorption pump and a thermosyphon. The developed sorption cooler aims to pre-cool a certain amount of the magnetic refrigerant of an adiabatic demagnetization refrigerator (ADR) from 4.5 K to 2.5 K. To simulate the high heat capacitance of the magnetic refrigerant, liquid helium was utilized not only as a refrigerant for the sorption cooling but also as a thermal capacitor. The previous experiment, however, showed that the lowest temperature of 2.7 K which was slightly higher than the target temperature (2.5 K) was achieved due to the radiation heat leak. This excessive heat leak would not occur when the sorption cooler is completely integrated with the ADR. Thus, based on the experimentally obtained pumping speed, the prediction model for the sorption cooler is developed in this study. The presented model in this paper assumes the sorption cooler is integrated with the ADR and the heat leak is negligible. The model predicts the amount of the liquid helium and the required time for the sorption cooling process. Furthermore, it is confirmed that the performance of the sorption cooler is enhanced by reducing the volume of the thermosiphon. The detailed results and discussions are summarized.

수소충전용 직접 및 간접 냉각시스템 비교 평가 연구 (The Study of Comparison of Cooling System for H2 Discharge Station)

  • 이현찬;이종열;배찬효;허정호;전재영
    • 한국수소및신에너지학회논문집
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    • 제30권2호
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    • pp.163-169
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    • 2019
  • This study is a research to compare efficiency of new cooling system (chiller, pre-cooler) to that of the conventional system at the hydrogen refueling station (HRS). This study includes contents for thermodynamic comparison of cooling system for HRS and comparison of pros and cons of its components. So It is to establish design concept of cooling system of HRS supplying with fuel cell electric vehicle (FCEV). HRS is charging high pressure H2 (700 bar) to FCEV. However cooling system is need to prevent temperature rise in tank. This cooling system consists of pre-cooler and chiller system.

헬리컬코일형 $CO_2$ 가스쿨러의 열전달과 압력강하 (Heat Transfer and Pressure Drop of $CO_2$ Gas Cooler in a Helically Coiled Tube)

  • 경남수;유태근;손창효;오후규
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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    • pp.246-247
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    • 2005
  • The paper presents the heat transfer characteristics during cooling process of carbon dioxide($CO_2$) in a helically coiled tube. The main components of the apparatus consist of a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section with the inner diameter 4.55 [mm] is a tube in tube type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The main results were summarized as follows : The heat transfer coefficient increases with respect to the decrease of the gas cooler pressure in a supercritical region and the increase of the refrigerant mass flux. The pressure drop decreases in increases of the gas cooler pressure and increases with respect to increases the refrigerant mass flux.

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초임계 영역에서 수평관내 $CO_2$ 열전달과 압력강하 (The heat transfer and pressure drop characteristics of $CO_2$ during supercritical region in a horizontal tube)

  • 이동건;오후규;김영률;손창효
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권3호
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    • pp.500-508
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    • 2004
  • The heat transfer coefficients during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments are conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater, and a gas cooler(test section). The water loop consists of a variable-speed pump, an isothermal tank, and a flow meter. The gas cooler is a counterflow heat exchanger by cooled water flowing in the annulus. The $CO_2$ flows in the horizontal stainless steel tube. which is 9.53mm in O.D. and 7.75mm in I.D. The gas cooler is 6 [m] in length. which is divided into 12 subsections, respectively. The experimental conditions considered in the study are following range of variables : refrigerant temperature is between 20 and $100^{\circ}C$. mass fluxes ranged from 200 to 400kg/($m^2$.s), average pressure varied from 7.5 to 10.0MPa. The main results were summarized as follows : The friction factors of $CO_2$ in the gas cooler show a relatively good agreement with those predicted by Blasius' correlation. The local heat transfer coefficient in the gas cooler has compared with most of correlations, which are the famous ones for forced convection heat transfer of turbulent flow. The results show that the local heat transfer coefficient of gas cooler agrees well with the correlation by Bringer-Smith except that at the region near pseudo critical temperature. while that at the near pseudo critical temperature is higher than the correlation.

흡습 냉각 원리를 이용한 소형 냉각 패드에 관한 연구 (Conceptual Development of a Subminiature Cool Pad Applying Sorption Cooling Effect)

  • 황용신;이대영;김우승
    • 설비공학논문집
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    • 제16권2호
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    • pp.121-127
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    • 2004
  • This paper describes conceptual development and idea-verification of a sub-miniature portable cooler which dose not necessitate any pre-cooling nor any external energy supply. The basic principle of the cooling mechanism is the vaporization of water and sub-sequent cooling due to the evaporative latent heat loss. In this work, the vaporization of the water is stimulated by desiccant material to improve the cooling effect. The evaporative cooling caused by the desiccant is modeled and analyzed considering the sorption characteristics of the desiccant. In addition, the portable cooler is fabricated in the shape of a thin pad, and its cooling characteristics are tested and compared with the analytic results.

경사진 헬리컬 코일형 가스냉각기의 관형상에 따른 $CO_2$ 냉각 열전달 특성 (Cooling Heat Transfer Characteristics of $CO_2$ on Tube Geometry of Inclined Helical Coil Type Gas Coolers)

  • 손창효;오후규
    • 설비공학논문집
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    • 제19권9호
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    • pp.640-646
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    • 2007
  • The cooling heat transfer coefficient of $CO_2$ (R-744) for tube and coil diameter (CD), inclined angle of tube and coil pitch of inclined helical coil type copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55 mm inner diameter (ID). The refrigerant mass flukes were varied from 200 to 800 [$kg/m^2s$] and the inlet pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in inclined helical coil tube with 2.45 mm ID are $5{\sim}10.3%$ higher than those of 4.55 mm. The heat transfer coefficients of 41.35 mm CD are $8{\sim}32.4%$ higher than those of 26.75 mm CD. Comparison between $45^{\circ}\;and\;90^{\circ}$ of coil angle, the heat transfer coefficients of $45^{\circ}$ are higher than those of $90^{\circ}$. For coil pitch of gas cooler, the heat transfer coefficients of inclined helical coil gas cooler with coil pitch of 5 mm are similar to those of 10 and 15 mm.

코일직경변화에 따른 헬리컬 코일형 가스냉각기내 초임계 이산화탄소의 냉각열전달 특성 (Heat Transfer Characteristics of Supercritical $CO_2$ in Helical Coil Gas Coolers on the Change of Coil Diameters)

  • 손창효
    • 한국가스학회지
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    • 제11권3호
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    • pp.44-48
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    • 2007
  • 본 연구는 코일직경변화에 따른 헬리컬 코일 가스냉각기내 초임계 $CO_2$의 냉각 열전달 특성에 대해 실험적으로 조사하였다. 냉매 순환루프의 주요구성품은 수액기, 변속펌프, 질량유량계, 예열기, 헬리컬 코일형 가스냉각기(시험부)로 구성된다. 시험부는 내경 4.55 mm의 평활 동관과 26.75 mm와 41.35 mm인 코일직경으로 이루어져 있다. 냉매질량유속은 $200kg/m^2s$에서 $800kg/m^2s$가지 변화시켰고, 가스냉각기의 입구압력 범위는 7.5 MPa에서 10.0 MPa까지이다. 코일직경이 26.75 mm인 가스냉각기내 이산화탄소의 냉각열전달 계수가 코일직경이 41.35 mm인 열전달 계수보다 높은 것으로 나타났다. 또한 초임계 상태에서 제안한 종래의 냉각 열전달 상관식과 비교한 결과, 대부분의 상관식이 과소예측되었고, 그 중에서도 이산화탄소의 냉각 열전달 계수는 Pilta 등이 제안한 상관식과 좋은 일치를 보였다. 하지만, 유사임계 온도 영역부근에서는 실험데이터가 더 큰 것으로 나타났다.

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수평관내 $CO_2$의 초임계 영역내 열전달에 관한 연구 (The heat transfer characteristics of supercritical $CO_2$ in a horizontal tube)

  • 오후규;이동건;손창효
    • Journal of Advanced Marine Engineering and Technology
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    • 제29권5호
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    • pp.526-532
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    • 2005
  • The cooling 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 gas cooler(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 $400\;kg/m^{2}s$ and the inlet cooling pressure of 7.5 MPa to 10.0 MPa. The variation of heat transfer coefficient tends to decrease as cooling pressure of $CO_2$ increases. The heat transfer coefficient with respect to mass flux increases as mass flux increases. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with that predicted by Blasius's correlation. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Bringer-Smith.