Solar Drying: Fundamentals,Applications and Innovations - National ...

Visavale, G.L., Principles, Classification and Selection of Solar Dryers. In Solar drying: Fundamentals,
Applications and Innovations, Ed. Hii, C.L., Ong, S.P., Jangam, S.V. and Mujumdar, A.S.,
2012, ISBN - 978-981-07-3336-0, Published in Singapore, pp. 1-50.
Chapter 1
Principles, Classification and Selection of Solar Dryers
G. L. Visavale
Computational Fluid Dynamics Division, Centre for Computational Technologies Pvt. Ltd. Pune-
411007, India
*Email: ganesh@cctech.co.in
Contents
1.1. INTRODUCTION ......................................................................................................................... 3
1.2. DRYING PRINCIPLES ................................................................................................................ 4
1.2.1. Psychrometry in Drying ................................................................................................................ 5
1.3. MECHANISM OF DRYING ........................................................................................................ 7
1.3.1. Internal Mechanism of Liquid Flow ......................................................................................... 7
1.3.2. Periods of Drying ............................................................................................................................. 8
1.3.2.1. Constant-Rate Period ............................................................................................................. 9
1.3.2.2. Falling-Rate Period ................................................................................................................. 9
1.3.2.3. Estimations for Total Drying Time ................................................................................. 10
1.4. WATER ACTIVITY, {αw}................................................................................................... 10
1.5. EQUILIBRIUM MOISTURE CONTENT ........................................................................... 10
1.6. SORPTION ISOTHERMS ........................................................................................................ 10
1.6.1. Sorption Equations........................................................................................................................ 11
1.6.2. The Bet Equation ............................................................................................................................ 12
1.6.3. GAB Equation................................................................................................................................... 12
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