# Thermal Evaluation of a Hybrid Dryer with Solar and Geothermal Energy for Agroindustry Application
## 3 Results  
### Controlled Conditions in the Laboratory: Solar Dryer  
Experimental tests set the parameters that would allow us to understand the thermal response of the drying chamber with forced flow (turbulent flow) at an air rate of 1.5 m/s and the variation of direct radiation. It should be noted that the speed set in the tests was the same as determined in the theoretical calculations. In addition, it should be noted that no direct irradiation tests were performed below 200 W/m\({}^{2}\), so that the operation of the dryer was low (heated up 5 \({}^{\circ}\)C more in relation to the ambient temperature). Finally, by performing the tests by triplicate, calibration errors of the instruments and measurement by the operator could be detected.  
Figure 2 shows the operating results of the dryer for the different irradiations and thermal stability time of the chamber obtained from the multiple tests performed for an operating speed of 1.5 m/s. By adapting the drying chamber with the solar collector (Figure 2a), it was observed that the maximum temperatures reached at 300 W/m\({}^{2}\) were 37.5 \({}^{\circ}\)C, 42.2 \({}^{\circ}\)C to 400 W/m\({}^{2}\), 46 \({}^{\circ}\)C to 500 W/m\({}^{2}\), 49.9 \({}^{\circ}\)C to 600 W/m\({}^{2}\), 55 \({}^{\circ}\)C to 700 W/m\({}^{2}\), 59.1 \({}^{\circ}\)C to 800 W/m\({}^{2}\), 65.5 \({}^{\circ}\)C to 900 W/m\({}^{2}\), and 67.8 \({}^{\circ}\)C to 1000 W/m\({}^{2}\)  
from the laboratory's ambient temperature of 27 \({}^{\circ}\)C. It can also be seen that the camera stabilized from 40 min from 300 to 500 W/m\({}^{2}\); from 600 W/m\({}^{2}\), the temperature stabilization time was one hour. On the other hand, during the cooling period, the chamber was estimated to have a decrease in the interior temperature between 1 to 2 \({}^{\circ}\)C every 10 min in the first hour. Subsequently, the internal temperature slowly decreased by an average value of 0.25 \({}^{\circ}\)C every 10 min until the temperature loss curve slowly decreased. In Figure 2b, it can be observed that the maximum temperatures reached in the solar collector was 37 \({}^{\circ}\)C to 300 W/m\({}^{2}\), 40 \({}^{\circ}\)C to 400 W/m\({}^{2}\), 43 \({}^{\circ}\)C to 500 W/m\({}^{2}\), 46 \({}^{\circ}\)C to 600 W/m\({}^{2}\), 50 \({}^{\circ}\)C to 700 W/m\({}^{2}\), 52 \({}^{\circ}\)C to 800 W/m\({}^{2}\), 57 \({}^{\circ}\)C to 900 W/m\({}^{2}\), and 59 \({}^{\circ}\)C to 1000 W/m\({}^{2}\).  
Figure 3 presents the results of the temperature increase of the dryer in tests carried out under controlled conditions at an ambient temperature of 27 \({}^{\circ}\)C. A temperature increase in the drying chamber was achieved (Figure 3a) between 10 to 15 \({}^{\circ}\)C for irradiations between 300 W/m\({}^{2}\) and 400 W/m\({}^{2}\) (conditions of a cloudy sky). On the other hand, the linear trend presented by the data estimated a temperature increase of more than 18 to 23 \({}^{\circ}\)C under conditions of a semi-cloudy sky (500 W/m\({}^{2}\) and 600 W/m\({}^{2}\)); from 800 W/m\({}^{2}\), it can be considered as clear sky, which is a temperature increase of more than 28 \({}^{\circ}\)C. In relation to Figure 3b, it can be observed that the solar collector at low irradiations generated a temperature increase of 8 to 12 \({}^{\circ}\)C more in relation to the ambient temperature. In general, the energy input of the solar collector allows for the temperature of the drying chamber to be raised, in addition to keeping the system stable for longer once the lamps are turned off.  
Figure 3: Difference between the internal temperature and the ambient temperature vs. irradiation in the (**a**) drying chamber, and (**b**) solar collector.  
Figure 2: Average temperature reached in the (**a**) drying chamber and (**b**) solar collector.