The changing aspects of energy and its high demand during convective drying of food products prompted this present study, which aims at investigating the impact of product geometric shapes and process parameters on the energy demand of vegetables during convective drying. It considered three distinctive shapes (sphere, S g ; cylinder, C g ; and slab, R g ) of vegetables (cucumber, garden egg, and white carrot) at constant sample volume, dried in a laboratory convective dryer. The Box-Behnken Design tool was used to design the experiment and explored the effects of material geometries at varying drying conditions (air temperature: 50, 60, and 70 C; air velocity: 1.0, 1.5, and 2.0 ms −1 ) on the total and specific drying energy demand, drying efficiency, percent product shrinkage, and drying time of the fresh vegetables. Results obtained revealed that the spherical-shaped samples exhibited high moisture diffusion and gross reduction in drying time (120 min), thus greater potential for energy and drying system improvement. The values of the effective moisture diffusion, D e (0.72 × 10 −10 ≤D e ≤ 2.13 × 10 −9 m 2 s −1 ) increased with drying temperature, and the maximum D e -value was obtained for the S g -carrot sample. The percent product shrinkage ranged between 78.66-94.73% for the C g -garden egg and S g -cucumber samples, respectively. The specific energy demand of the fresh cucumber, eggplant, and white carrot samples varied significantly (p >.005) with sample geometry. The maximum specific energy demand (16.38 ± 0.41 MJ/kgH 2 O, respectively) was obtained for the cylindrical shaped samples, whereas the minimum specific energy demand of 9.06 ± 0.24 MJ/kgH 2 O was yielded by the spherical shaped samples. The mean energy and drying efficiencies of the system ranged from 3.25 to 12.26% and 7.22 to 28.24%, respectively; whilst drying time ranged between 470 and 840 min.At the optimum process variables of 69.85 C, 1.22 ms −1 , 0.999 geometric shape, and −0.9977 crop sample, the specific energy demand, drying time, drying efficiency, and percent shrinkage were found to be 14.21 ± 0.84 MJkg −1 , 820 ± 9.00 min, 22.76 ± 0.74%, and 92.104 ± 1.00%, respectively. Prospects for future application and recommendations for further studies were suggested.
The determination of mechanical properties of unshelled Moringa oleifera seeds was studied under compression test at varying orientations and moisture contents for postharvest equipment design. A completely randomized block design (CRBD) was applied in designing the experiment. The impact of varying moisture content levels of (10.25, 17.33, 24.47, and 32.34% dry basis) on the applied force at bio-yield and rupture, deformation, energy at rupture, crushing strength, and elastic modulus of the seed samples were investigated. Polynomial functions of the 2nd order with coefficients of correlation ranging between 0.642 ≤ R2 ≤ 0.999 gave the best fit and described the resulting relationships between the studied properties with respect to moisture levels at the two loading axes. Results obtained showed that the seed samples had maximum values of 80.3 N, 110 N and 257.2 J, for bio-yield force, rupture and rupture energy respectively at (10.25% d.b., in the horizontal orientation; whereas minimum values of 31.5 N, 54.9 N and 51.3 J for bio-yield force, rupture force and rupture energy occurred at (32.34% d.b.) respectively in the vertical orientation. Also, the maximum compressive strength of 5.8 N mm-2 in the horizontal orientation of the seed samples at 10.25% d.b. whereas the minimum compressive strength (2.5 N mm-2) occurred in the vertical orientation at 10.25% d.b. moisture content. The sample exhibited less resistive strength to crushing in the horizontal position as the moisture increased; whereas in the vertical position, the cell’s vertical edges provide some form of shield against external pressure which resulted in increased crushing resistance per contact area of the sample.
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