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. 2021 Oct 28;11(1):21266.
doi: 10.1038/s41598-021-00690-z.

Kinetics, energy efficiency and mathematical modeling of thin layer solar drying of figs (Ficus carica L.)

Lahcen Hssaini  1 , Rachida Ouaabou  2 , Hafida Hanine  3 , Rachid Razouk  4 , Ali Idlimam  5
Affiliations

Kinetics, energy efficiency and mathematical modeling of thin layer solar drying of figs (Ficus carica L.)

Lahcen Hssaini et al. Sci Rep. .

Erratum in

Abstract

First convectional thin layer drying of two fig (Ficus carica L.) varieties growing in Moroccan, using partially indirect convective dryer, was performed. The experimental design combined three air temperatures levels (60, 70 and 80 °C) and two air-flow rates (150 and 300 m3/h). Fig drying curve was defined as a third-order polynomial equation linking the sample moisture content to the effective moisture diffusivity. The average activation energy was ranged between 4699.41 and 7502.37 kJ/kg. It raised proportionally with the air flow velocity, and the same pattern were observed for effective moisture diffusivity regarding drying time and velocity. High levels of temperature (80 °C) and velocity (300 m3/h) lead to shorten drying time (200 min) and improve the slices physical quality. Among the nine tested models, Modified Handerson and Pabis exhibited the highest correlation coefficient value with the lowest chi-square for both varieties, and then give the best prediction performance. Energetic investigation of the dryer prototype showed that the total use of energy alongside with the specific energy utilization (13.12 and 44.55 MWh/kg) were inversely proportional to the velocity and drying temperature. Likewise, the energy efficiency was greater (3.98%) higher in drying conditions.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Schematic diagram of the solar dryer. (1) Solar collector, (2) circulation fan, (3) fan, (4) air flow direction, (5) control box, (6) auxiliary heating system, (7) shelves, (8) drying cabinet, (9) recycling air, (10) control foot, (11) exit of air, (12) humidity probes and (13) thermocouples (14) sample holder (Ouaabou et al.).
Figure 2
Figure 2
Air relative humidity, temperature (A) and solar radiation (B) on the dryer collector during the experiment of drying air temperature of 60 °C.
Figure 3
Figure 3
Drying time as a function of temperatures and drying volume flow rate.
Figure 4
Figure 4
Experimental curves of fig moisture content as a function of time, at various air temperatures (60, 70 and 80 °C) and drying volume flow rate (150 and 300 m3/h).
Figure 5
Figure 5
Drying rate of fig slices as a function of drying time. Curves for each temperature are embedded separately.
Figure 5
Figure 5
Drying rate of fig slices as a function of drying time. Curves for each temperature are embedded separately.
Figure 6
Figure 6
Pictures of the whole fruits and their dried slices at 80 °C and 300 m3/h. (a–d) refer to ‘Conidria’ and ‘Rey Blanche’, respectively.
Figure 7
Figure 7
Characteristic drying curve of fig (a) and dimensionless drying rate versus moisture ratio of Rey Blanche and Conidria varieties (b).
Figure 8
Figure 8
Plot of Ln(Y*) versus drying time in different drying air conditions for both fig varieties ‘Rey Blanche’ and ‘Conidria’.
Figure 9
Figure 9
Ln(Deff) versus 1/T for both fig varieties at different air flows drying.
Figure 10
Figure 10
Experimental data of moisture ratio versus drying time fitted with modified Handerson and Pabis model at Dv = 150 m3/h.
Figure 11
Figure 11
Comparison of experimental and predicted moisture ratio for both fig varieties by modified Handerson and Pabis model.
Figure 12
Figure 12
Energy consumption and specific energy consumption (SEC) during convection solar drying of fig slices at different aero-thermal conditions.
Figure 13
Figure 13
Energy efficiency for drying of fig slices at different drying air temperatures and flow rates.
See this image and copyright information in PMC

References

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