• 제목/요약/키워드: heat-freeze

검색결과 138건 처리시간 0.022초

다공성 물길의 진공동결건조과정에서 얼 및 물질전달 특성에 관한 연구 (A Study on the Heat and Mass Transfer Characteristics of Vacuum Freeze Drying Process for Porous Media)

  • c. s. song
    • Journal of Advanced Marine Engineering and Technology
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    • 제25권6호
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    • pp.1341-1352
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    • 2001
  • Vacuum freeze drying process by which frozen water in a drying material is removed sublimation under vacuum condition, is now applied to various industrial field such as the manufacturing and packaging of pharmaceuticals in pharmaceutical industry, the drying of bio- products in bio-technology industry, the treatment of various quality food stuff in food technology, and so on. The Knowledge about the heat and mass transfer characteristics related with the vacuum freeze drying process is crucial to improve the efficiency of the process as well as the quality of dried products. In spite of increasing needs for understanding of the process, the research efforts in this fields are still insufficient. In this paper, a numerical code that can predict primary drying in a vial is developed based on the finite volume method with a moving grid system. The calculation program can handle the axis- symmetric and multi-dimensional characteristics of heat and mass transfer of the vial freeze drying process. To demonstrated the usefulness of the present analysis, a practical freeze drying of skim Milk solution in a vial is simulated and various calculation results are presented.

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동결층소멸을 이용한 동결건조 속도에 관한 연구 (A Study on the Freeze Drying Rate with Frozen Layer)

  • 홍성선;이희명;오창섭
    • 설비공학논문집
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    • 제2권2호
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    • pp.105-111
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    • 1990
  • The drying rate in freeze drying was obtained by experiment of garlic moisture contents depending on the drying time. Freeze drying experiment of garlic juice was carried out in vaccum freeze drier of laboratory scale by backface heating, and a mathematical model is also used to simulate the process of simultaneous heat and mass transfer in freeze drying to compare with experimental data.

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폴리카보실란 에멀젼의 동결건조를 이용한 다공체 SiC 제조 (Preparation of Porous SiC by Freeze Drying of Polycarbosilane Emulsion)

  • 황연
    • 한국재료학회지
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    • 제26권6호
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    • pp.320-324
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    • 2016
  • Porous SiC beads were prepared by freeze-drying a polycarbosilane (PCS) emulsion. The water-in-oil (w/o) emulsion, which was composed of water, PCS dissolved p-xylene, and sodium xylenesulfonate (SXS) as an emulsifier, was frozen by dropping it onto a liquid $N_2$ bath; this process resulted in 1~2 mm sized beads. Beads were cured at $200^{\circ}C$ for 1 h in air and heat-treated at $800^{\circ}C$ and $1400^{\circ}C$ for 1 h in an Ar gas flow. Two types of pores, lamella-shaped and spherical pores, were observed. Lamellar-shaped pores were found to develop during the freezing of the xylene solvent. Water droplets in the w/o emulsion were changed into spherical pores under freeze-drying. At $1400^{\circ}C$ of heat-treatment, porous SiC was synthesized with a low level of impurities.

냉동건조에 의한 잎담배 팽화특성 (Characterization of Expanded Tobacco Lamina Tissues by Freeze Drying)

  • 김병구
    • 한국연초학회지
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    • 제17권2호
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    • pp.149-159
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    • 1995
  • The freeze drying rate was investigated under various conditions such as pressure and moisture contents in order to establish the optimum condition for expansion of the culled flue cured tobacco lamina. The optimal pressure in the chamber to maintain the heat and mass transfer was about 0.8torr, When the moisture contents of sample was 50-60%, expanding rate was the optimum condition and the rate was 67-76%. As the thickness of the sample layers was increased, drying-rate was decreased conversely and this result seemed to be due to decline of heat and mass transfer coefficients. Differences with the position of its stalk were also observed in drying rate, and low stalk position leaves of 5 and 3 was the fastest. Key words : freeze drying, Popping, expansion tobacco.

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Evaluation of durability performance for maintenance of tunnel structures due to repeated freezing and thawing

  • Jai-Wook An;Joon-Shik Moon;Hong-Kyoon Kim
    • Geomechanics and Engineering
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    • 제38권6호
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    • pp.593-601
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    • 2024
  • In this paper, the quantitative evaluation method is presented for the durability performance of mountain tunnel concrete linings experiencing freezing and thawing during winter season. To analyze the freeze-thaw characteristics of lining, the freezing time of the concrete lining was measured by the outside temperature. The heat flow analysis was conducted based on the freezing time measured through the indoor experiment, and based on this, the energy required to freeze the concrete lining by the temperature of the outside air could be analyzed. In addition, the temperature change during the winter season was measured through an instrument installed on the actual tunnel concrete lining, and based on the results of indoor and field experiments, criteria for freeze-thaw environment evaluation and progress evaluation were prepared. Also, an equation using the freezing index was proposed through regression analysis.

고정격자계에서 유한체적법을 이용한 진공동결건조 과정의 열 및 물질전달에 대한 연구 (A Fixed Grid Finite Volume Analysis of Multi-Dimensional Freeze Drying Process under Vacuum Condition)

  • Chi-Sung, Song
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권6호
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    • pp.981-992
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    • 2004
  • Freeze drying under vacuum condition is a complex process that involves simultaneous heat and mass transfer, sublimation of ice, and motion of sublimation front. Proper treatment of the motion of sublimation interface is crucial for an accurate prediction of the freeze drying process. Based on the enthalpy formulation that has been successfully used in liquid/solid phase change problems. a fixed grid method. streamlined for the freeze drying analysis. was developed in this study. The accuracy of the fixed grid method was checked by solving a one-dimensional tray freeze drying and a two-dimensional vial freeze drying problem and then comparing the results with those by the moving grid method. Finally. the freeze drying characteristics of two-dimensional slab and axis-symmetric cylinder was investigated using the fixed grid method.

비등온 평판의 이성분 합금 냉각코팅에 관한 수치해석 (A Numerical Analysis on the Freeze Coating of a Non-Isothermal Flat Plate with a Binary Alloy)

  • 남진현;김찬중
    • 대한기계학회논문집B
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    • 제24권11호
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    • pp.1437-1446
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    • 2000
  • A numerical analysis on the freeze coating process of a non-isothermal finite dimensional plate with a binary alloy is performed to investigate the growth and decay behavior of the solid and the mushy layer of the freeze coat and a complete procedure to calculate the process is obtained in this study. The continuously varying solid and mushy layers are immobilized by a coordinate transform and the resulting governing differential equations are solved by a finite difference technique. To account for the latent heat release and property change during solidification, proper phase change models are adopted. And the convection in the liquid melt is modeled as an appropriate heat transfer boundary condition at the liquid/mushy interface. The present results are compared with analytic solutions derived for the freeze coating of infinite dimensional plates and the discrepancy is found to be less than 0.5 percent in relative magnitude for all simulation cases. In addition the conservation of thermal energy is checked. The results show that the freeze coat grows proportional to the 1.2 square of axial position as predicted by analytic solutions ar first. But after the short period of initial growth, the growth rate of the freeze coat gradually decreases and finally the freeze coat starts to decay. The effects of various non-dimensional processing parameters on the behavior of freeze coat are also investigated.

녹용 및 녹각의 단백질 가수분해 효소 및 염산에 의한 가용화 (Extraction of Young Antler and Antler by Water, Proteases and HCl)

  • 안용근
    • 한국식품영양학회지
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    • 제17권2호
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    • pp.147-155
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    • 2004
  • 동결건조 녹용, 열건조 녹용, 녹각을 물, pretense, 염산으로 단계적으로 추출하였다. 5$0^{\circ}C$ 물로 추출한 경우 동결건조 녹용은 9.01%(흡광도 8.82), 열건조 녹용은 9.01%(흡광도 4.45), 녹각은 1.10%(흡광도 0.31)의 추출율을 나타냈고, 세균 protease로 추출한 경우는 동결건조녹용은 16.89%(흡광도 4.50), 열건조 녹용은 17.20%(흡광도 5.62), 녹각은 18.22%(흡광도 0.64)의 추출율을 나타냈고, 0.8N 염산으로 추출한 경우는 동결건조 녹용은 72.25%(흡광도 4.60), 열건조 녹용은 71.1%(흡광도 4.70), 녹각은 79.82%(흡광도 2.80)의 추출율을 나타냈다. 이들 삼단계 과정으로 동결건조 녹용은 98.15%, 열건조 녹용은 97.35%, 녹각은 99.14% 추출되었다. HPLC로 분석한 결과, 녹용 및 녹각추출물에서 나타나는 고분자 피크는 단백질 가수분해 효소의 작용으로 분자량 1,000 정도의 작은 피크로 분해되었고 남은 각질은 0.8 N염산에 의하여 분자량 7만 정도의 단백질이 추출되었다. 이상의 결과로부터 동결 건조녹용의 추출에는 물과 protease에 의한 추출, 열건조 녹용의 추출에는 protease와 염산에 의한 추출, 녹각의 추출에는 염산에 의한 추출이 효과적이었다.

고정격자를 이용한 동결건조 해석프로그램의 개발 (Development of Freeze Drying Analysis Program using Fixed Grid)

  • 남진현;송치성;김찬중
    • 설비공학논문집
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    • 제16권10호
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    • pp.923-931
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    • 2004
  • A multi-dimensional freeze drying analysis program, which took simultaneous heat and mass transfer, sublimation of ice and motion of sublimation front into full account, was developed using finite volume method with fixed grid. The effect due to the motion of sublimation interface was modeled by an enthalpy formulation streamlined for the freeze drying problems. The efficiency and accuracy of the program was validated by solving one- and two-dimensional freeze drying problems frequently encountered in industrial processes. Finally, the freeze drying processes of cylinder and slab objects with permeable side surfaces were simulated, which demonstrated the capability of the present analysis program in solving multi-dimensional freeze drying problems with complex sublimation interface configurations.

자연순환형 태양열온수기 동파방지기술 (Freeze Protection for Passive Solar Water Heating System)

  • 김종현;홍희기;정재동
    • 설비공학논문집
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    • 제23권5호
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    • pp.327-333
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    • 2011
  • In the present work, a new freeze protection method has been proposed for a natural circulation system of solar water heater. Though electrothermal wire is popularly used for the purpose, there are freezing troubles by wire cut-off and shortage of excessive electric power consumption. In the experimental device, hot water in storage tank was used to heat the outlet pipe from the tank if the pipe surface temperature falls lower than a set point. The cold water pipe to the storage tank was installed to directly contact the hot water pipe surface temperature rose by transferred heat.