African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 6560

Full Length Research Paper

Kinetics and thermodynamic properties of the drying process of sorghum (Sorghum bicolor [L.] Moench) grains

Osvaldo Resende
  • Osvaldo Resende
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil.
  • Google Scholar
Daniel Emanuel Cabral de Oliveira
  • Daniel Emanuel Cabral de Oliveira
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil.
  • Google Scholar
Tarcísio Honório Chaves
  • Tarcísio Honório Chaves
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil.
  • Google Scholar
Jaqueline Ferreira
  • Jaqueline Ferreira
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil.
  • Google Scholar
Vieira Bessa
  • Vieira Bessa
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil.
  • Google Scholar
Osvaldo Resende
  • Osvaldo Resende
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil.
  • Google Scholar
Daniel Emanuel Cabral de Oliveira
  • Daniel Emanuel Cabral de Oliveira
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar
Tarcísio Honório Chaves
  • Tarcísio Honório Chaves
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar
Jaqueline Ferreira
  • Jaqueline Ferreira
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar
Vieira Bessa
  • Vieira Bessa
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar
Osvaldo Resende
  • Osvaldo Resende
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil.
  • Google Scholar
Daniel Emanuel Cabral de Oliveira
  • Daniel Emanuel Cabral de Oliveira
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar
Tarcísio Honório Chaves
  • Tarcísio Honório Chaves
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar
Jaqueline Ferreira
  • Jaqueline Ferreira
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar
Vieira Bessa
  • Vieira Bessa
  • Federal Institute of Education, Science and Technology Goiás, Rio Verde, GO, Rod 01 Km South of Goiás, Zona Rural, Rio Verde – GO, Brazil
  • Google Scholar


  •  Received: 25 April 2014
  •  Accepted: 26 June 2014
  •  Published: 04 August 2014

Abstract

The goal of this work was to fit several mathematical models to the experimental data from the drying of sorghum (Sorghum bicolor [L.] Moench) grains of the AS4620 cultivar, to determine and evaluate the effective diffusion coefficient, to obtain the activation energy and to determine the thermodynamic properties of the drying process at different temperatures and air speeds. The initial moisture content of 0.228 ± 0.003 on a dry basis (d.b., decimal), were subjected to drying in an experimental dryer where the drying air speed was kept at either 0.5 or 1.0 m s-1, and for each speed, the system was set to heat at 40, 50 and 60°C until the moisture contents reached 0.137 ± 0.004 (d.b.). The Page model was selected to represent the drying phenomenon. The effective diffusion coefficient of the sorghum grains increased as temperature and air speed increased, and the pattern can be described by the Arrhenius equation, which provides activation energy values for liquid diffusion in the sorghum drying process of 27.12 and 42.05 kJ mol-1 for air speeds of 0.5 and 1.0 m s-1, respectively. When the drying temperature is increased, enthalpy and entropy decrease, whereas Gibbs free energy increases.

 

Key words: Mathematical modeling, activation energy, enthalpy, entropy, Gibbs free energy, Sorghum bicolor [L.] Moench, drying.