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Two identical prototype solar dryers (direct and indirect) having the same dimensions were used to dry whole mint. Both prototypes were operated under natural and forced convection modes. In the case of the later one the ambient air was entered the dryer with the velocity of 4.2 m s−1. The effect of flow mode and the type of solar dryers on the drying kinetics of whole mint were investigated. Ten empirical models were used to fit the drying curves; nine of them represented well the solar drying behavior of mint. The results indicated that drying of mint under different operating conditions occurred in the falling rate period, where no constant rate period of drying was observed. Also, the obtained data revealed that the drying rate of mint under forced convection was higher than that of mint under natural convection, especially during first hours of drying (first day). The values of the effective diffusivity coefficient for the mint drying ranged between 1.2 × 10−11 and 1.33 × 10−11 m2 s−1.

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Conducting physical attendance exams during pandemics is a challenge facing many educational institutes and universities. Our study’s main objective is to numerically simulate the expected transmission of the harmful exhaled droplets of aerosols from an infected instructor to students in an exam room ventilated by a number of spiral diffusers. Several critical parameters, including the droplet size, the ventilation rate, and status of the entrance door were considered in the analysis. Two dimensionless indices, i.e., the specific normalized average concentration (SNAC) and the exceedance in exposure ratio (EER), were introduced to examine the effect of the said parameters on student exposure to the harmful droplets. The study revealed that the 5 mm droplets were less hazardous as they resulted in an 87% reduction in exposure when compared with the small 1 mm size droplets. We also found that when the ventilation rate ratio (VRR) increased above unity, an upward entrainment process, due to the swirl diffuser, of the aerosol droplets took place, and consequently the risk of student exposure was reduced. The results also demonstrated that increasing VRR from zero to 1 and then to 2 decreased the exceedance in the student exposure from 3.5 to 2.15 and then to less than zero, respectively. The study also showed that keeping the lecture room’s main door open is recommended as this reduced the risk of exposure by 26% in the case of a VRR equal to 2.

This investigation was carried out at Plant Production Department, Faculty of Agriculture (Saba-Basha), Alexandria University, Egypt and Cotton Arbitration and Testing General Organization (CATGO), Egypt, on some Egyptian cotton varieties, and some drying instruments, during 2018/2019 season. Six commercial Egyptian cotton varieties, G. barbadense representing the two categories of Egyptian cotton were used. The first group represents the Extra-long staple, extra fine (ELS) category these varieties were Giza 87 and Giza 96 (over 1 3/8-inch fiber length = > 35 mm). The second group represented the long staple (LS) category (1 1/4-1 3/8-inch fiber length =30:34 mm) included long staple white i.e., Giza 86, Giza 94 and Long staple creamy i.e., Giza 95 and Giza 90. The Aqua Lab, Good Brand Jefferys(NEW), Good Brand (Developed), and H.V.I classing 1000 were used to determine the moisture, physical and mechanical properties. The Extralong cotton varieties had a highly significant effect on fiber properties the highest mean value of fiber length (UHML) (35.60 mm), uniformity index (88.09%) were recorded for the Egyptian cotton variety Giza 87. The highest mean value of fiber strength (44.33 g/tex), spinning consistency index (SCI) (223.75) were shown by the Egyptian cotton variety Giza 96. The long staple varieties had a highly significant effect on the fiber properties the maximum value of micronaire reading (4.56), short fiber index (7.02%), maturity index (0.87) were recorded by the Egyptian cotton variety Giza 95. The highest mean value of fiber elongation (7.62%) was shown by the Egyptian cotton variety Giza 90. The maximum value reflectance degree (RD) (78.52%). The drying instruments differed significantly for five properties i.e., fiber strength, short fiber index, spinning consistency index, reflectance degree and yellowness degree. The maximum value of the short fiber index (6.32%) was shown after Good Brand (New). The highest mean value of fiber strength (40.57g/tex), spinning consistency index(SCI) (192.88) were recorded after Aqua Lab. The maximum value of reflectance degree (RD) (73.85%) was shown before drying treatment. The highest mean value of yellowness degree (+b) (10.84) was recorded after Good Brand (Developed). The Egyptian cotton varieties(V) revealed highly significant differences for all moisture properties i.e., moisture regains (MR) and moisture content (MC). The highest mean value of moisture regain (MR) (8.32%), moisture content (MC) (7.68%) were shown by the Egyptian cotton variety Giza 87. Concerning the drying instruments(I) revealed highly significant differences for moisture properties. The highest mean value of moisture regain(MR) (7.75%), moisture content (MC) (7.68%) were recorded by Good Brand (dev.).

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