To realize energy-saving and efficient industrial grain drying, the present work studied the variable-temperature drying process of corn drying in a novel industrial corn-drying system with a heat recycling and self-adaptive control function. The drying kinetics, thermal performance, heat-loss characteristics and the heat-recycling performance of the drying system under different allocations between flue gas and hot air were investigated, and the optimized drying process was proposed and compared with two constant drying processes. The results showed that the optimized drying process exhibited better drying kinetic and thermal performance than the two constant drying processes. More specifically, the total heat loss, total energy consumption and specific energy consumption of the optimized drying process were ascertained to be 36,132.85 MJ, 48,803.99 MJ and 7290.27 kJ/kg, respectively, which were lower than those of the other two processes. On the other hand, the thermal efficiency of the drying chamber for the optimized drying process was ascertained to be varied within the range of 6.81–41.71%. Overall, the validation results showed that the optimized drying process can significantly improve the drying performance of the drying system.

An online corn moisture content measurement device would be a key technology for providing accurate feedback information for industrial drying processes to enable the dynamic tracking and closed-loop control of the process. To overcome the problem of large measurement error caused by the characteristics of the corn flow state and the pore distribution when a parallel plate capacitor is applied to the online moisture content measurement process, in this study, we summarized the constraint conditions of the sensor’s structure parameters by mathematical modeling and calculated the optimal sensor design size. Moreover, the influence of porosity variation on moisture content measurement was studied by using the designed sensor. In addition, a mathematical model for calculating corn moisture content was obtained for the moisture content range of 14.7% to 26.4% w.b., temperature of 5 °C to 35 °C, and porosity of 38.4% to 44.6%. The results indicated that the fluctuation in the online moisture content measurement value was obviously reduced after the porosity compensation. The absolute error of the measured moisture content value was −0.62 to 0.67% w.b., and the average of absolute values of error was 0.32% w.b. The main results provide a theoretical basis and technical support for the development of intelligent industrial grain–drying equipment.

Recently, heat pump drying has been widely used in tobacco processing. Considering the importance of this issue, it is of significant importance to further investigate temperature distribution and energy analysis in the drying process. To develop an energy-saving, environmental-friendly, and high-quality tobacco drying method, temperature distribution, dehumidification performance, the economic issues, and thermal efficiency of a heat pump curing barn (HPCB) and a traditional coal-fired bulk curing barn (TCCB) were compared. The regional temperature eigenvalue model was applied to describe the temperature uniformity with HPCB and TCCB. Moreover, thermal efficiency was obtained through energy tests. The obtained results showed that HPCB is beneficial to improve the drying quality of tobacco. The performed analyses showed that the thermal efficiency of the TCCB and HPCB was 42.02% and 66.53%, respectively. Accordingly, heat pump technology is recommended for industrial drying of tobacco leaves and obtaining high-quality products.

The heat exchanger is the key component of an industrial drying system. The present work introduced a novel tube heat exchanger into a corn drying system. To fully understand the heat exchange process and optimize the heat exchange performance of the heat exchanger, numerical simulation, exergy analysis and economic analysis methodologies were adopted to analyze the comprehensive performance of the heat exchanger. The fluid dynamics as well as the exergy performance of the heat exchanger under different flue gas velocities (3, 5 and 7m/s) and different ambient air relative humidities (80%, 85% and 90%) were investigated. The results showed that there are two strong turbulences causing the huge pressure drop at the last two stages of the flue gas duct, while there are two insufficient heat exchange areas on both sides of the heat exchanger; thus, the corresponding improvement recommendations were proposed in the present work. The values of the $\mathrm{Re}$ and $Nu$ were found to vary in the range of 1256.275–2210.554 and 21.337–32.415, respectively. The average heat transfer coefficients were ascertained to be above 8.274 kW·m⁻²·K⁻¹, while the pressure drop of the ambient air was ascertained to be under 16.138 Pa. Moreover, the exergy analysis revealed that the heat exchanger experiences sustainable development ($SI$ < 2), and the exergy efficiency is above 11.461%. The main results may provide some references for further optimizing the heat transfer performance of the heat exchanger.