An Effective Moisture Diffusivity Model Deduced from Experiment and Numerical Solution of Mass Transfer Equations for a Shrinkable Drying Slab of Microalgae Spirulina

Abstract

From experimental data, Spirulina effective moisture diffusivity was analytically estimated by considering two diffusion regions and the product shrinkage. Then, the moisture diffusivity was deduced from the numerical solutions of mass transfer equations by minimizing the difference between experimental and simulated drying curves and by taking into account the slab thickness variation. The range of moisture diffusivity used for simulations was estimated from minimal and maximal values of experimental effective diffusivities and calculation started with the mean value of experimental effective diffusivities. Identified effective diffusivities ranged from 1.79 × 10⁻¹⁰ to 6.73 × 10⁻¹⁰ m²/s. These diffusivities increased strongly with drying temperature and decreased slightly with moisture content. A suitable model correlating effective diffusivity, temperature, and moisture content was then established. Effective diffusivities given by this model were very close to experimental ones with a relative difference ranging from 0.5 to 24%.

Keywords:

• Diffusivity
• Drying
• Heat
• Mass transfer
• Modeling
• Shrinkage
• Spirulina

Notes

⁽¹⁾Classical method of slopes.

⁽²⁾Method of slopes suggested by Pinto and Tobinaga^{[ 15 ]} and by Vagenas and Karathanos.^{[ 33 ]}

⁽¹⁾Classical method of slopes.

⁽²⁾Method of slopes suggested by Pinto and Tobinaga^{[ 15 ]} and by Vagenas and Karathanos.^{[ 33 ]}

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