Overview
ABSTRACT
Drying is a process which allows for the transformation of the initial "humid" (either solid or liquid) state of a product into a final state so called "dry solid". In order to achieve this, a part of the solvent must be removed from the product in order to obtain a finished product under the solid, "divided solid" or powder form. This article is dedicated to explaining the various drying processes, as well as the consequences on the transformation of the product and its final quality. In order to achieve this, two different drying processes are presented. The hot-air convective drying and the forced convective drying processes are explained in detail through the properties of humid air, matter and enthalpy assessments on the product and the air, transfers and limiting phenomena, etc.
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Read the articleAUTHOR
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Jean VASSEUR: Engineer GREF – Doctor Engineer - Professor at AgroParisTech-Massy (formerly ENSIA) – UMR 1145
INTRODUCTION
This article is the first in a series devoted to the principles and calculations of industrial dryers, consisting of :
and "Hot-air convection drying" (parts 1 and 2).
"Other drying methods than hot air".
It is completed by three diagrams of humid air , , .
For practical aspects and dryer selection, please refer to the dossier written by Patricia ARLABOSSE (ENSTIMAC).
This first article describes the physical laws associated with the various drying principles, which can lead to quite different "hydrothermal histories" followed by the product, with consequences for the transformation of the product during the process, and therefore for its final quality. We'll provide you with the bases for calculating dryers, concerning heat and material balances, and the transfers that determine the duration of treatment and the size of installations. The appearance of porosity, the texture of the final product and/or its deformation during the process are also drying parameters to be considered.
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Drying: principles and equipment calculation
General drying considerations
Bibliography
Reviews
Journals dealing with the drying unit operation, independently of the product:
Chemical Engineering Science ;
Chemical Engineering Processing ;
Drying Technology Journal ;
International Journal of Thermal Science ;
Journal of Heat and Mass Transfer...
Software tools
Collection of psychrometry software http://www.linric.com
Online psychrometric calculation http://www.psychro.com
Commercial "Dryer 3 000" software [Windows, MacOSX or Unix/Linux], for calculating cereal tower dryers, by simulation using...
Events
IDS Congress: International Drying Symposium (number of the year)
International congress dedicated to drying. It takes place every two years, in a different host country. The proceedings of each congress are available for consultation.
Directory
AFSIA: French Drying Association for Industry and Agriculture
It brings together applied drying research centers, researchers and manufacturers in France. Its headquarters can change (in 2008, INSA Lyon). It organizes or participates in conferences, and produces its own publications (AFSIA publications).
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