Modeling and Experimental Analysis of a Dual-collector Indirect Solar Dryer for Intermittent and Continuous Drying of Bioproducts
Emmanuel Sidwaya Sawadogo *
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
Salmwendé Eloi Tiendrebeogo
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso and Department of Physics, High school of Education, Ouagadougou, Burkina Faso.
Guy Christian Tubreoumya
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
André Luc Batiana
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
Windnigda Zoungrana
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
Téré Dabilgou
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
Jacques Nébié
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
Oumar Bailou
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
Alfa Oumar Dissa
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
Antoine Béré
Laboratory of Physics and Environmental Chemistry, Joseph KI-ZERBO University, Ouagadougou, Burkina Faso.
*Author to whom correspondence should be addressed.
Abstract
This study presents the development and experimental validation of a coupled heat and mass transfer model for a dual-collector indirect solar dryer based on the energy balance of a representative section of the system. The governing equations describe the simultaneous evolution of collector temperature, drying air temperature and product moisture content while accounting for solar irradiance variations of up to 1050 W m⁻², convective heat transfer and both continuous and intermittent drying modes. Experimental tests were conducted on banana (Musa paradisiaca) and sweet potato (Ipomoea batatas), with a loading capacity of 1.5 kg for each product and an intermittency ratio of α = 0.5 under a controlled drying temperature below 60 °C. Temperature profiles, dry-basis moisture content and drying rates were determined and analysed for both operating configurations. The results showed favourable thermal conditions for drying, characterised by a gradual increase in temperature and enhanced mass transfer during the initial drying stage. Moisture content decreased from approximately 1.4 to 1.2 kg water kg⁻¹ dry matter for banana and from 3.0 to 2.6 kg water kg⁻¹ dry matter for sweet potato, indicating rapid evaporation of free water. Maximum drying rates of 5.6 and 6.3 kg water kg⁻¹ dry matter min⁻¹ were recorded for banana and sweet potato, respectively, demonstrating the intensity of heat and mass transfer at the beginning of the process. Comparison of continuous and intermittent drying modes showed that intermittency reduced the overall drying rate while stabilising thermal and moisture gradients. Numerical predictions were in good agreement with experimental observations, confirming the reliability of the proposed model. The observed discrepancies were mainly attributed to climatic fluctuations and simplifying assumptions adopted in the model.
Keywords: Thermo-mass transfer modelling, heat and mass transfer, solar drying, experimental validation, intermittent drying regime.