3.5 The “ Big Equation ”
4.1.3 Solar and Skylight
Drying time is an important factor in agro-based industial process. Most agricultural products come in wet conditions and need to be dried to required standard moisture content at a given time interval. Variations in thermal conductivity of the variously treated ginger samples at various drying temperatures with respect to drying time are shown in tables 4.10 to 4.15. Figures 4.7 to 4.12 present the effect of drying time on the thermal conductivities of the variously treated ginger samples.
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Table 4.10 Variations in Thermal Conductivity of the variously treated ginger samples at drying temperature of 𝟏𝟎℃
Time (Hour)
Thermal Conductivity (unblanched)
Thermal Conductivity (blanched)
Thermal Conductivity (unpeeled)
Thermal Conductivity (peeled)
𝑾
𝒎. 𝑲 𝑾
𝒎. 𝑲 𝑾
𝒎. 𝑲 𝑾
𝒎. 𝑲
2 0.4064 0.329 0.3397 0.3768
4 0.3188 0.2878 0.3093 0.3004
8 0.2657 0.1993 0.2657 0.2623
10 0.2303 0.1901 0.2329 0.2115
14 0.1834 0.1699 0.2205 0.1919
16 0.1727 0.1558 0.2093 0.1658
24 0.1607 0.14 0.1713 0.1449
Figure 4.7 Variations of Thermal Conductivities of the Ginger samples at a drying temperature of 100C
Figure 4.7 present the variations of thermal conductivity with drying time at drying temperature of 10⁰C. The best fit to the data was found to be logarithmic and
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45
0 5 10 15 20 25 30
ThermalCoductivity (𝑾/(𝒎.𝑲))
Drying Time (hour)
Thermal Conductivity (unblanched) Thermal Conductivity (blanched) Thermal Conductivity (unpeled) Thermal Conductivity (peeled)
78
polynomial of second order trend. The thermal conductivities for the variously treated samples decrease with time, which implies that as time progresses, less amount of moisture is lost. The thermal conductivity of unblanched treated sample reduced from 0.4064W/mK to 0.1607W/mK within the twenty four hours drying time. The thermal conductivity of blanched treated sample reduced from 0.3397W/mK to 0.1713W/mK within the twenty four hours drying time. The thermal conductivity of unpeeled treated sample reduced from 0.329W/mK to 0.14W/mK within the twenty four hours drying time. The thermal conductivity of peeled treated sample reduced from 0.3768W/mK to 0.1449W/mK within the twenty four hours drying time.
Table 4.11 Variations in Thermal Conductivity of the ginger samples at drying temperature of 𝟐𝟎℃
Time(Hour)
Thermal Conductivity (unblanched)
𝑾 𝒎. 𝑲
Thermal Conductivity (blanched)
𝑾 𝒎. 𝑲
Thermal Conductivity (unpeeled)
𝑾 𝒎. 𝑲
Thermal Conductivity (peeled)
𝑾 𝒎. 𝑲
2 0.4064 0.2919 0.3454 0.3768
4 0.3188 0.2527 0.3343 0.3238
8 0.2382 0.2228 0.2839 0.2839
10 0.1974 0.1742 0.2329 0.2115
14 0.1901 0.157 0.2205 0.1818
16 0.1658 0.1449 0.1802 0.1594
24 0.1491 0.1312 0.1713 0.1391
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Figure 4.8 Variations of Thermal Conductivities of the Ginger samples at a drying temperature of 200C
Figure 4.8 present the variations of thermal conductivity with drying time at drying temperature of 20⁰C. Also, the best fit to the data was found to be logarithmic and polynminal of second order trend. Also, the thermal conductivities for the variously treated samples decrease with time. It could be seen that as time increases, the thermal conductivity of blanched treated sample reduced as low as 0.1312W/mK.
Table 4.12 Variations in Thermal Conductivity of the ginger samples at drying temperature of 𝟑𝟎℃
Time(Hour)
Thermal Conductivity (unblanched)
Thermal Conductivity (blanched)
Thermal Conductivity (unpeeled)
Thermal Conductivity (peeled)
2 0.1074 0.1006 0.1126 0.1459
4 0.0996 0.0913 0.1021 0.1132
8 0.0987 0.081 0.081 0.0909
10 0.0955 0.08 0.074 0.0776
14 0.0809 0.0761 0.0658 0.0715
16 0.0785 0.0732 0.063 0.0693
24 0.0677 0.0689 0.0611 0.0652
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45
0 5 10 15 20 25 30
Thermal Coductivity (𝑾/(𝒎.𝑲))
Drying Time (hour)
Thermal Conductivity (unblanched) Thermal Conductivity (blanched) Thermal Conductivity (unpeled) Thermal Conductivity (peeled)
80
Figure 4.9 Variations of Thermal Conductivities of the Ginger samples at a drying temperature of 300C
The variations of thermal conductivity with drying time at drying temperature of 30⁰C is shown in figure 4.9. Also, the best fit to the data was found to be logarithmic and polynminal of second order trend. As expected the thermal conductivities for the variously treated samples decrease with time. It could be seen that as time increases, the thermal conductivity of unpeeled treated sample reduced as low as 0.0611W/mK.
Table 4.13 Variations in Thermal Conductivity of the ginger samples at drying temperature of 𝟒𝟎℃
Time(Hour)
Thermal Conductivity (unblanched)
Thermal Conductivity (blanched)
Thermal Conductivity (unpeeled)
Thermal Conductivity (peeled)
2 0.0756 0.0707 0.0717 0.0717
4 0.0691 0.0662 0.0658 0.071
8 0.066 0.0648 0.0611 0.0662
10 0.0638 0.0636 0.0572 0.0624
14 0.0608 0.0606 0.056 0.059
16 0.0581 0.0574 0.0557 0.0548
24 0.0557 0.0562 0.0543 0.0516
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16
0 5 10 15 20 25 30
Drying Time (hour)
Thermal Conductivity (unblanched) Thermal Conductivity (blanched) Thermal Conductivity (unpeled) Thermal Conductivity (peeled)
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Figure 4.10 Variations of Thermal Conductivities of the Ginger samples at a drying temperature of 400C
The variations of thermal conductivity with drying time at drying temperature of 40⁰C is shown in figure 4.10. The best fit to the data was found to be logarithmic and polynminal of second order trend. As expected the thermal conductivities for the variously treated samples decrease with time. It shows that as time increases to twenty fours, the thermal conductivity of peeled treated sample reduce to 0.0516W/mK.
Table 4.14 Variations in Thermal Conductivity of the ginger samples at drying temperature of 𝟓𝟎℃
Time(Hour)
Thermal Conductivity (unblanched)
Thermal Conductivity (blanched)
Thermal Conductivity (unpeeled)
Thermal Conductivity (peeled)
2 0.0715 0.073 0.0776 0.0759
4 0.0698 0.065 0.071 0.0695
8 0.0675 0.0626 0.0622 0.0634
10 0.0652 0.061 0.0596 0.0571
14 0.0582 0.0584 0.054 0.0555
16 0.0563 0.0581 0.0465 0.0543
24 0.0541 0.0556 0.046 0.0519
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
0 5 10 15 20 25 30
Thermal Coductivity (𝑾/(𝒎.𝑲))
Drying Time (hour)
Thermal Conductivity (unblanched) Thermal Conductivity (blanched) Thermal Conductivity (unpeled) Thermal Conductivity (peeled)
82
Figure 4.11 Variations of Thermal Conductivities of the Ginger samples at a drying temperature of 500C
Figure 4.11 present the variations of thermal conductivity with drying time at drying temperature of 50⁰C. The best fit to the data was found to be logarithmic and polynminal of second order trend. The thermal conductivities for the variously treated samples decrease with time, while unpeeled treated sample exhibited the least value of thermal conductivity.
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
0 5 10 15 20 25 30
Thermal Coductivity (𝑾/(𝒎.𝑲))
Drying Time (hour)
Thermal Conductivity (unblanched) Thermal Conductivity (blanched) Thermal Conductivity (unpeled) Thermal Conductivity (peeled)
83
Table 4.15 Variations in Thermal Conductivity of the ginger samples at drying temperature of 𝟔𝟎℃
Time(Hour)
Thermal Conductivity (unblanched)
Thermal Conductivity (blanched)
Thermal Conductivity (unpeeled)
Thermal Conductivity (peeled)
2 0.0762 0.0836 0.0776 0.0791
4 0.072 0.0762 0.0689 0.0727
8 0.0695 0.0732 0.0622 0.0664
10 0.0691 0.0576 0.0596 0.0611
14 0.0652 0.0566 0.054 0.0557
16 0.0644 0.0536 0.0465 0.0534
24 0.0553 0.0516 0.046 0.0483
Figure 4.12 Variations of Thermal Conductivities of the Ginger samples at a drying temperature of 600C
Figure 4.12 present the variations of thermal conductivity with drying time at drying temperature of 60⁰C. The best fit to the data was found to be logarithmic and polynminal of second order trend. The thermal conductivities for the variously treated samples decrease with time. Also, the initial thermal conductivities for the various
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
0 5 10 15 20 25 30
Thermal Coductivity (𝑾/(𝒎.𝑲))
Drying Time (hour)
Thermal Conductivity (unblanched) Thermal Conductivity (blanched) Thermal Conductivity (unpeled) Thermal Conductivity (peeled)
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treatments decrease with temperature. The thermal conductivity is highest at 2 hours and falls significantly until it reaches a drying time of 24 hours. The trend is highest at 10°C - 20°C and fall significantly at 30°C - 60°C for the various samples.
The drying characteristics of Nigeria ginger rhizomes investigated showed that the drying process employed could be accelerated only during the early stages of the drying process where air and mass movement are external factors which influence the drying rate. The unpeeled and blanched ginger rhizomes are also influenced by the presence of moisture barrier such as the unpeeled skins. As the study reveals, drying of ginger rhizomes at low temperatures of 10°C – 20°C does not have much significance on drying behaviour as it maintains high initial moisture content and high thermal conductivity. However, as the temperature increases above 60°C ginger rhizomes becomes sensitive to temperature both in texture and color. The author opines that drying of ginger rhizomes could be accomplished at a temperatures between 50⁰C to 60°C in order to maintain the desired drying criteria.