• 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.

• Journal of the Korean Wood Science and Technology
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• 제41권5호
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• pp.456-465
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• 2013

Log cross sections of yellow poplar were dried in a radio frequency vacuum (RFV) dryer under alternating vacuum and release (AVR) process. The average moisture content (MC), temperature and vapor pressure at the volumetric center were monitored as functions of time. Three different log thicknesses (33, 60 and 75mm) were tested. The results show that the AVR process caused an increase in the drying rate when the moisture content was above fiber saturation point (FSP, about 30% MC) but that it had an inverse effect on the drying rate when the MC was below FSP. The effect of the AVR process on the drying rate decreased, and the severity of heart checks increased, with the increase in the thickness of the specimens.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.58-66
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• 2016

저온진공건조 조건에 따른 곶감의 건조특성 및 품질적 변화를 분석하였다. 곶감의 건조 특성은 전형적인 항율건조기간과 감율건조기간이 존재함을 확인 할 수 있었다. 진공압력이 높을수록 가열온도가 높을수록 곶감의 당도, 당 함량, 경도 값은 높게 나타났으며 이에 비해 명도 값은 낮게 나타남을 알 수 있었다. 기존 천일 및 열풍건조를 대처할 수 있는 진공건조의 최적 조건은 진공압력이 40~50kPa abs., 가열온도 $30^{\circ}C$, 건조시간은 3~4일 이었다.

• Journal of the Korean Wood Science and Technology
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• 제30권2호
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• pp.108-114
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• 2002

변장 14.0 cm와 16.5 cm인 소나무 정각재의 가열판진공건조와 고주파진공건조간의 건조속도, 함수율분포와 비(比)에너지를 비교하였다. 고주파진공건조는 가열판진공건조보다 건조속도 및 변장이 건조속도에 미치는 영향이 컸었다. 가열판진공건조 목재의 재장방향, 두께방향과 폭방향의 함수율분포는 볼록 형태를 나타내었고, 고주파진공건조 목재는 오목 형태를 나타내었다. 가열판진공건조 목재의 폭방향과 두께방향간의 수분경사는 유사하였으나 고주파진공건조 목재의 경우는 폭방향의 수분경사가 두께방향보다 완만하였다. 가열판진공건조와 고주파 진공건조의 비(比)에너지곡선은 함수율이 감소할수록 증가하는 경향을 나타내었고, 가열판진공건조의 비(比)는 고주파진공건조보다 컸었다.

• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.226-232
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• 2002

In tradition, there have been two kinds of drying methods, which are sun drying and artificial drying. The sun drying method which has been adopted traditionally has been replaced by the hot-air drying method which is one of the most general methods of artificial drying, with its simple drying system, low initial cost of drying plant, and easy operating method. But the hot-air drying method has some defects ; (1)much energy loss happens due to the discharge of hot air during the drying process, (2)control of drying rate is not easy on account of changing relative humidity of inlet air for uniform hot air temperature, (3)high temperature of floods in drying process brings about the production of low-grade drying products. Also, the hot-air drying method is inducing environmental and sanitary problems which are resulting from the emission of high temperature and high humidity air, including stick on the drying progress. Vacuum drying technique, whose drying time and 7uantity of exhausting energy is about 1/3 ~1/4 of hot air drying, is very excellent in the drying efficiency. As the results, it took about 20 hours for material to reach about 18% of the final moisture content in order to store products for a long time, from about 470% of the early moisture content at the beginning of drying, and maximum drying rate comes to about $0.35 kg/m^2hr$ at about 350% of the moisture content.

• 동력기계공학회지
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• 제5권1호
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• pp.44-49
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• 2001

Low temperature vacuum drying technique shows very excellent energy efficiency and prominent drying performances compared with the conventional hot air drying technique. This study was focused on the thermal characteristics of the low temperature vacuum drying technique. From the results of this study, it was confirmed that the time consumption for drying with the new drying technique could be shortened to about 1/3 of the time consumption with the conventional hot air drying technique under the same drying conditions for wet products. Also, the maximum drying rate with the new drying technique reached to about $0.35kg/m^2h$ at about 400% of moisture content.

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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• pp.427-434
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• 2000

In tradition, there have been two kinds of drying methods, which are sun drying and artificial drying. The sun drying method which has been adopted traditionally has been replaced by the hot-air drying method which is one of the most general methods of artificial drying, with its simple drying system, low initial cost of drying plant, and easy operating method. But the hot-air drying method has some defects; (1) much energy loss happens due to the discharge of hot air during the drying process, (2) control of drying rate is not easy on account of changing relative humidity of inlet air for uniform hot air temperature, (3) high temperature of foods in drying process brings about the production of low-grade drying products. Vacuum drying takes advantage of energy saving and mass production because it reduces the drying time by increasing the drying rate under low temperature condition. The aim of this paper is to develop the low temperature vacum dryer, with low initial investments and operating costs, easy operating method and trouble-free operation.

• 설비공학논문집
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• 제28권5호
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• pp.208-215
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• 2016

This study was conducted to improve the performance of low-temperature vacuum dryer by applying desiccant to cold trap. Performance evaluation was carried out using several desiccants. The amounts of absorption and diffusivity were measured based on analytic model. Results of desiccant performance evaluation revealed that silica-gel had the most excellent performance for conditions of low-temperature vacuum drying process. Silica-gel was applied to cold trap for evaluating the drying performance. The experiment results showed that the drying time was extended as the thickness of sample was increased due to increased heat and mass transfer resistance of drying sample. In addition, as heating plate temperature was increased, drying time was decreased due to increased evaporation pressure of drying sample. Furthermore, drying time with desiccant was decreased approximately 20% than that without desiccant.

• 공업화학
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• 제35권1호
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• pp.42-47
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• 2024

벤튜리를 이용한 진공건조 공정에 의해 폐 감귤박으로부터 리모넨을 분리하고 건조된 감귤박을 이용하여 바이오 에탄올을 생산하였다. 벤튜리를 이용한 진공건조가 열풍건조 및 자연건조에 비해 수분 및 리모넨의 제거에 매우 효과적이었으며, 벤튜리 진공건조에 의해 건조된 감귤박이 에탄올 발효에 가장 적절하였다. 벤튜리 진공건조에 의해 15시간 동안 건조된 감귤박의 수분 및 리모넨 함량은 각각 17.0% 및 3.2%이었다. 벤튜리 진공건조에 의해 리모넨을 함유한 정유와 플로럴 워터를 각각 얻을 수 있었으며, 벤튜리 진공건조에 의해 분리된 정유의 양은 4.21 mL/kg 감귤박이었고, 분리된 정유의 79.9%는 리모넨이었다.

• 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.