The Effects of Sublimation-Condensation Region on Heat and Mass Transfer During Microwave Freeze Drying

1998 ◽  
Vol 120 (3) ◽  
pp. 654-660 ◽  
Author(s):  
Zhao Hui Wang ◽  
Ming Heng Shi
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Heat And Mass Transfer ◽  
Freeze Drying ◽  
Experimental Results ◽  
Interface Model ◽  
Unsaturated Porous Media ◽  
Drying Time ◽  
Condensation Model ◽  
Moisture Redistribution

The sublimation-condensation model, developed for freeze drying of unsaturated porous media in the author’s previous work, is analyzed numerically. The moisture redistribution in the sublimation-condensation region is taken into account in this model. The calculations show that the saturation of ice in the sublimation-condensation region will obviously decrease, and its effects on heat and mass transfer cannot be neglected for microwave freeze-drying of unsaturated porous media. The microwave freeze-drying tests of unsaturated beef are carried out. The experimental results show that the drying time is approximately proportional to the initial saturation of beef. Moreover the sublimation-condensation model is validated by the experimental results. These results show that the sublimation-condensation model agrees better with experimental results than the sublimation interface model.

Conjugate heat and mass transfer process within porous media with dielectric cores in microwave freeze drying

2004 ◽  
Vol 59 (14) ◽  
pp. 2921-2928 ◽  
Author(s):  
Hongwei Wu ◽  
Zhi Tao ◽  
Guohua Chen ◽  
Hongwu Deng ◽  
Guoqiang Xu ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Heat And Mass Transfer ◽  
Transfer Process ◽  
Freeze Drying ◽  
Mass Transfer Process

Heat and mass transfer in unsaturated porous media with solid-liquid change

2001 ◽  
Vol 37 (2-3) ◽  
pp. 237-242 ◽  
Author(s):  
T.-J. Lu ◽  
J.-H. Du ◽  
S.-Y. Lei ◽  
B.-X. Wang
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Heat And Mass Transfer ◽  
Unsaturated Porous Media ◽  
Solid Liquid

scholarly journals Model for Heat and Mass Transfer in Freeze-Drying of Pellets

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Ioan Cristian Trelea ◽  
Stéphanie Passot ◽  
Michèle Marin ◽  
Fernanda Fonseca
Keyword(s):  
Mass Transfer ◽  
Moisture Content ◽  
Product Quality ◽  
Heat And Mass Transfer ◽  
Freeze Drying ◽  
Chamber Pressure ◽  
Bulk Temperature ◽  
Slab Thickness ◽  
Drying Time ◽  
Drying Conditions

Lyophilizing frozen pellets, and especially spray freeze-drying, have been receiving growing interest. To design efficient and safe freeze-drying cycles, local temperature and moisture content in the product bed have to be known, but both are difficult to measure in the industry. Mathematical modeling of heat and mass transfer helps to determine local freeze-drying conditions and predict effects of operation policy, and equipment and recipe changes on drying time and product quality. Representative pellets situated at different positions in the product slab were considered. One-dimensional transfer in the slab and radial transfer in the pellets were assumed. Coupled heat and vapor transfer equations between the temperature-controlled shelf, the product bulk, the sublimation front inside the pellets, and the chamber were established and solved numerically. The model was validated based on bulk temperature measurement performed at two different locations in the product slab and on partial vapor pressure measurement in the freeze-drying chamber. Fair agreement between measured and calculated values was found. In contrast, a previously developed model for compact product layer was found inadequate in describing freeze-drying of pellets. The developed model represents a good starting basis for studying freeze-drying of pellets. It has to be further improved and validated for a variety of product types and freeze-drying conditions (shelf temperature, total chamber pressure, pellet size, slab thickness, etc.). It could be used to develop freeze-drying cycles based on product quality criteria such as local moisture content and glass transition temperature.

Sign in / Sign up

Export Citation Format

Share Document