## 3 Results and Discussion
### Experimental Evaluation of the Solar Dryer
#### 3.1.1 Taro (Colocasia esculenta)  
Due to cloudiness, solar radiation had significant variations, which caused fluctuations in the air temperature at the entrance to the drying chamber. Three important aspects are combined in the phenomenology corresponding to the drying process: forced ventilation, the impossibility of maintaining constant the temperature of the air surrounding the samples, and the porosity of the taro. Due to its porosity, the critical moisture content in taro is high, which implies that the samples have a greater amount of water in the last drying stage (decreasing drying stage) and higher drying velocity than the plantain. The drying curves reflect the problem of migrating from the free moisture content zone and reaching the equilibrium moisture content, causing disturbances in the drying velocity curves. This is because the heat transfer rate is different from the mass transfer rate, which does not allow constant drying rates, and sudden changes occur since the concentration gradient decreases, sharply decelerating the mass transport and delaying the filling of water in the interstitial spaces of the taro by capillarity. However, the temperature gradient between the inlet of the solar collector and the outlet of the drying chamber could be maintained, and, despite the disturbances during the test, the evaporative drying conditions and behaviors were established. In Figure 4, the drying curves for taro are observed, which were sectioned according to the deviations that occur in the drying velocity. The choice of the time ranges indicated in the subfigures was given by observing changes in the drying velocity curves, which showed different stages within the dryer. On the other hand, the derivative of the moisture content on a dry basis was considered because the drying speed was evaluated through the variations of the mass per unit of time, for each sampling period. In the case of the fan voltage at 6 V Figure 4(a1,b1), the drying time ranges were 0 to 200 min, 200 to 300 min, 300 to 450 min, and 450 to 525 min, with average drying velocities for each region of 1.8, 1.5, 0.9, and 0.3 g/min, respectively. These correspond to the changes in the dry basis moisture curve in the same ranges. According to the figures, despite the environmental conditions, the drying process stages were present, and a more stable drying velocity in the decreasing drying region was achieved, with a decrease of 33% compared to the previous region. In this case, the solar radiation and the ambient temperature conserved almost  
Figure 4: Curves of dry basis moisture (**a**) and drying velocity (**b**) for _taro_ at different fan voltages (\(V_{f}\)): **(a1,b1)**\(V_{f}\) = 6 V; **(a2,b2)**\(V_{f}\) = 9 V; **(a3,b3)**\(V_{f}\) = 12 V.  
temperature remained oscillating between 40.7 \({}^{\circ}\)C and 41.5 \({}^{\circ}\)C, helping the drying process in its last stage. In the case of the 12 V fan voltage (Figure 4(a3,b3)), the observed drying time ranges were from 0 to 270 min, from 270 to 405 min, and from 405 to 465 min, with average drying velocities for each region of 1.6, 1.17, and 0.53 g/min, respectively. These results correspond to the changes in the rate of variation of the dry basis moisture. Except for a disturbance at the beginning of drying, solar radiation remained with a favorable rate of change, maintaining its morphology concerning ambient temperature, including during the last hour and a half of the test where the decrease in solar radiation and ambient temperature agreed with the drastic decrease in drying speed. The average drying velocity decreased by 45.3% in the last time range, corresponding to the stability zone of the drying velocity.