Influence of Drying Temperature on the Different Thermodynamic Parameters during the Indirect Convective Solar Drying of Crocus sativus L. Of Morocco Thin-Layer Solar Drying of Moroccan Saffron

This work deals with the study of the drying kinetics of Crocus sativus L. using convective solar drying. The main objective was to identify the influence of airflow drying temperatures for ambient air temperature ranged between 15.6 and 18.9°C, and a relative humidity between 24.4 and 46.5%. The equilibrium moisture content varies from 0.09 to 0.06 (% d.b), respectively, for drying air temperatures 35-50°C. The airflow velocity was about 0.2 m s-1, which implied establishing a phenomenological diffusion model of the water within the matrix. Empirical models were also determined as well as a polynomial equation (order 3) of the characteristic drying curve. The Midilli-Kucuk model was found to be the best to describe the experimental drying curves of Crocus sativus L. The effective moisture diffusivity ranged between 0.87 and 1.46 10-11 m2 s-1 for airflow temperature 35 and 50°C, while the average activation energy was calculated as 28.76 kJ mol-1. The increase in temperature decreases the total energy consumption which varies, respectively, from 3.211 to 2.681 kWh.

Study of the energetic, exergetic, and thermal balances of a solar distillation unit in comparison with a conventional system during the distillation of rosemary leaves

The solar energy produced by Scheffler parabola (10 m²) is not fully exploited by the solar distillation system of aromatic and medicinal plants. In this work, the optical losses in the primary and secondary reflectors, and the thermal losses at each part of this system (solar still, steam line, condenser) were determined. A thermal energetic and exergetic analysis were also performed for a solar distillation system of rosemary leaves. For average intensity radiation of 849.1W/m² and 6 Kg of rosemary leaves during 4 h of distillation, exergy and optical efficiencies of the system achieved up to 26.62% and 50.97%, respectively. The thermal efficiency of the solar still, steam line, and condenser is about 94.80%, 94.30%, and 87.76%, respectively. The essential oil yield per unit of consumed energy and the total efficiency of the solar distillation system, taking into account the heat losses in the solar still, steam line, and condenser, as well as the optical losses in the two reflectors, is 6.18 mL/ kWh and 40.00%, respectively. The efficiency can be as high as 42.42 % if the steam line is insulated. Moreover, the comparison between the solar steam distillation and conventional steam distillation shows that solar distillation is much more efficient since it gives better results and especially it avoids the emission of 12.10 kg of CO₂ during extraction.