## 3 Results and Discussion  
### The Influence of Ambient Temperature on the Energy and Exergy Performance of the Drying System  
In order to fully investigate the influence of ambient temperature on the drying behavior of the drying system, the experimental data in three days with different ambient temperatures and similar relative humidity (17 October: 8.07 \({}^{\circ}\)C \(\leq T_{0}\leq\) 13.41 \({}^{\circ}\)C, 42.51% \(\leq RH_{0}\leq\) 56.36%; 30 October: 3.26 \({}^{\circ}\)C \(\leq T_{0}\leq\) 8.87 \({}^{\circ}\)C, 47.26% \(\leq RH_{0}\leq\) 65.22%; 19 November: \(-\)0.74 \({}^{\circ}\)C \(\leq\)\(T_{0}\leq\) 5.18 \({}^{\circ}\)C, 40.35% \(\leq RH_{0}\leq\) 63.22%) are adopted for the analysis. The variations of corn moisture content and corn temperature with drying time are shown in Figure 5.  
The loading capacity of the dryer is considered to be 50,000 kg accuracy and the initial moisture content of the corn were also determined to be 32% d.b. for the three experimental days. As shown in Figure 5, _MC_ decreases with the increase of \(t\) while \(T_{c}\) slightly increases with the increase of \(t\) for the three sets of experimental data. The _MC_ decreases in a stepped way owing to the fact that corn drying is the circulate drying process, and the circulate time for each circle was ascertained to be 90 min. Similar drying process for agricultural product industrial drying were reported by [PERSON] et al. in 2017 [36]. The total drying time for a unit drying operation in 17 October, 30 October, and 19 November, are, respectively, ascertained to be 480, 540, and 600 min, indicating that the \(T_{0}\) has a great influence on \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Unit** & **Uncertainties** \\ \hline Ambient temperature & \({}^{\circ}\)C & \(\pm\)0.1 \\ Ambient relative humidity & \% & \(\pm\)0.3 \\ Flue gas temperature & \({}^{\circ}\)C & \(\pm\)0.2 \\ Outlet air relative humidity & RH & \(\pm\)0.3 \\ Corn moisture content & \% & \(\pm\)0.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._  
Figure 5: The variations of corn moisture content and corn temperature with drying time. the drying kinetics of the corn industrial drying. The \(T_{c}\) for the three sets of experimental data are less than 38 \({}^{\circ}\)C, as recommended by [PERSON], [PERSON] et al. [37]. Moreover, it can be obvious found that the \(T_{c}\) under the same drying time for the three days, in ascending order of values, are as follows: \(T_{c}\) in 19 November, \(T_{c}\) in 30 October, \(T_{c}\) in 17 October, which might be caused by the heat change efficiency of the heat exchanger. The exergy efficiency of the heat exchanger was calculated followed by Equation (4), and the results are depicted in Figure 6. As can be seen from the figure, even if the \(\eta_{ex,h}\) fluctuates a lot with the drying time, which might be caused by the fluctuating inlet flue gas temperature, it can be obviously found that \(\eta_{ex,h}\) in 17 October is higher than that in 30 October and 19 November. The \(\eta_{ex,h}\) for the three days, respectively, ranges from 0.391 to 0.648, 0.350 to 0.601, and 0.249 to 0.434. It is interesting that there is a clear upward trend of the \(\eta_{ex,h}\) for three days after 260 min owing to the fact that \(T_{0}\) rose up at noon for the three days. Accordingly, it can be concluded that the \(T_{0}\) has a significant influence on the heat exchange performance of the heat exchanger, as well as the drying performance of the whole drying process. Moreover, for the present industrial-scale drying system, the ambient conditions should not be considered as the dead state, the ambient temperature should be take into consideration when analyzing the energy and energetic performance of the dryer. Similar findings have been reported by [PERSON] et al. [38] for ambient air cereal grain drying; they developed a model for predicting the drying behavior based on the climatic data parameters (ambient temperature and relative humidity).