## 3 Results and Discussions  
### Drying Kinetics of the IRCC Corn Dryer  
The ambient and medium conditions during drying process are depicted in Figure 5. In the current work, the drying kinetics was used to evaluate the dryer performance; the \(MC\) and \(DR\) curves are depicted in Figure 6. The ambient temperature on the test day was relatively low, with an average of 8.83 \({}^{\circ}\)C. The average temperature of inlet air was 107.06 \({}^{\circ}\)C. The humidity of inlet air was affected by the real-time environment, with a fluctuation range of 3.71-4.02 g/kg and an average value of 3.83 g/kg.  
Figure 5: Ambient and medium conditions during drying process.  
The results show that the corn moisture content decreased from the initial value (27.95% w.b.) to the safe value (14.2% w.b.). The whole drying process lasted for 12 h (eight circulations) with the drying capacity of 4.2 t/h. The relationship between _MC_ and \(t\) was simulated by the experimental data, which can be described as _MC_ = _26.708 exp(-0.001t)_ (_R\({}^{2}\) = 0.9984_). In the initial stage of drying operation, the drying rate primarily increased rapidly and then decreased gradually with the advancing of drying process. The maximum and the final drying rate were, respectively 2.91 gwater/gwet matter h and 0.34 gwater/gwet matter h, and the average drying rate of corn drying system is 1.1 gwater/gwet matter h. Additionally, according to the drying rate, the corn drying process can be divided into three stages: warming up period, falling period I and falling period II. The amount of dehydration of drying process in four stages was 2056.162 kg, 3556.209 kg and 2044.45 kg, accounting for 25.66%, 44.38% and 29.96%, respectively, as depicted in the pie chart. The corn drying process of the developed dry in this paper presents different characteristics in different stages as described below.  
In warming up period (0-90 min), the moisture in corn with high moisture content is mainly free water, including water flowing in the capillary and adhering to the kernel [45]. Since the binding effect between free water and absolute dry matter is relatively tightly, the dehydration in this stage can be regarded as the evaporation process of free water. Hence, the partial pressure of water vapor on the corn surface increases gradually in the process that the corn temperature rises to the wet bulb temperature of drying medium [40], which results in the increasing drying rate. After the large number of free water is rapidly removed in warming up period, the moisture in corn is mainly physicochemical binding water [45], at this time, the drying process begins to go through the falling period I (90-330 min). In this period, water evaporation is limited by grain itself, and the corn drying process is the result of both surface evaporation and internal diffusion. The rate of surface evaporation depends on the size of evaporation area, and the internal water evaporation rate depends on the water diffusion of corn itself. In order to accelerate the water diffusion of grain itself, abundant energy is required to offset the binding energy between the water molecules and the attachment points while little energy is utilized to evaporate water [19], which results the reduced drying rate in this stage. With the continuous decrease of corn moisture content, the drying will experience the falling period II (after 330 min). In this period, corn is in the low-moisture region and the binding energy increases significantly with the drying process [28]. The drying rate will decrease with the decreasing partial pressure of water vapor around the grain surface. Similar results have also been found in the research to wheat [46], paddy [47] and corn [48].  
Figure 6: Kinetics curves of the corn drying process.