• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.2
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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.

• Korean Journal of Materials Research
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• v.26 no.6
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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.

• Journal of the Korean Society of Tobacco Science
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• v.17 no.2
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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.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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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.

• The Korean Journal of Food And Nutrition
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• v.17 no.2
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• pp.147-155
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• 2004

Freeze dried antler, heat dried antler, antler were extracted through processing step by water, protease and hydrochloric acid(HCl). Extraction rate of freeze dried antler at 50$^{\circ}C$ by water was 9.01％(8.82, absorbance at 280 nm), that of heat dried antler was 9.01％(4.45, absorbance at 280 nm), and that of antler was 1.10％(0.31, absorbance at 280 nm), respectively. Extraction rate of freeze dried antler by bacterial protease was 16.89％(4.50, absorbance at 280 nm), and that of heat dried antler was 17.29％(5.62, absorbance at 280 nm), and that of antler was 18.22％(0.64, absorbance at 280 nm), respectively. Extraction rate of freeze dried antler by 0.8N HCl was 72.25％(4.60, absorbance at 280 nm), that of heat dried antler was 71.14％(4.70 absorbance at 280 nm), and that of antler was 79.82％ (2.80, absorbance at 280 nm), respectively. Extraction rate of freeze dried antler through three processing steps was 98.15％, that of heat dried antler was 97.35％, that of antler was 99.14％, respectively. The result of analysis by HPLC shows that high molecular pe which appears in young antler and antler extraction was changed into a small molecular peak of about 1,000 by the reaction of protease, and protein of about MW 70,000 was extracted from their remaining residue by 0.8N HCl. The above result shows that water extraction and protease extraction in the freeze dried young antler, protease extraction and HCl extraction in dried young antler, and HCl extraction in antler are most effective.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.5
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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.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.349-357
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• 2022

Abnormal climate events are occurring frequently around the world. In particular, cold waves and heavy snow lead to damage and deterioration of facilities, which can cause loss of life or property damage, such as shortening the lifespan of facilities. Therefore, it is very important to prepare an appropriate maintenance system and to establish a strategy to cope with abnormal weather conditions. In this study, laboratory freezing experiments were performed to analyze the freeze-thaw characteristics affecting the tunnel concrete lining, and heat flow analysis was carried out based on the test results. Based on these experimental and theoretical analysis results, quantitative freeze-thaw evaluation criteria for tunnel concrete linings were proposed.