Theory of Drying

This review examines the stages of drying, with the emphasis on the constant rate period (CRP), when the pores are full of liquid. It is during the CRP that most of the shrinkage occurs and the drying stresses rise to a maximum. We examine the forces that produce shrinkage and the mechanisms respons...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1990-01, Vol.73 (1), p.3-14
Main Author: Scherer, George W.
Format: Article
Language:English
Subjects:
Applied sciences
cracking
Devices using thermal energy
Dryers
drying
Energy
Energy. Thermal use of fuels
Exact sciences and technology
gels
shrinking
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Summary:This review examines the stages of drying, with the emphasis on the constant rate period (CRP), when the pores are full of liquid. It is during the CRP that most of the shrinkage occurs and the drying stresses rise to a maximum. We examine the forces that produce shrinkage and the mechanisms responsible for transport of liquid. By analyzing the interplay of fluid flow and shrinkage of the solid network, it is possible to calculate the pressure distribution in the liquid in the pores. The tension in the liquid is found to be greatest near the drying surface, resulting in greater compressive stresses on the network in that region. This produces differential shrinkage of the solid, which is the cause of cracking during drying. The probability of fracture is related to the size of the body, the rate of evaporation, and the strength of the network. A variety of strategies for avoiding fracture during drying are discussed.
ISSN:0002-7820
1551-2916
DOI:10.1111/j.1151-2916.1990.tb05082.x