The multi-channel cylinder dryer (MCD) is designed to improve heat transfer. Although there are numerous research studies on the pressure drop, heat transfer characteristics, and flow pattern in static state of MCD, there is little research on the flow pattern in the rotating state. In this paper, the distribution of flow pattern in MCD under different rotating speeds and steam mass flow rates is studied. Furthermore, the logistic regression method (LR) is used to predict the flow pattern diagrams. The results show that in the front section of the flow channel, the flow pattern is basically annular flow, which is not affected by mass flow rate and rotating speed. On the other hand, wavy flow, vortex flow, slug flow, and bubble flow can be observed when the fluid enters the middle and the end section. The higher the rotating speed and the steam mass flow rate, the more the flow pattern tends to be an annular and wavy flow. At the end of the passage, the flow pattern is mainly slug flow. The predicted flow pattern diagrams are in good agreement with the experimental result, and to obtain an effective flow pattern in the middle and the end section of the flow channel, the influence of increasing rotating speed is greater than that of increasing steam mass flow rate. However, the specific rotating speed, steam mass flow rate, and other parameters should still be set by combining with the actual situation. This work can provide some references for the further study of MCD flow characteristics. © TAPPI Press 2023.

With the purpose of improving molded pulp product (MPP) drying process, the present work investigated the microwave drying performance of MPP under the power level of 500 W and compared that with the convective drying method. The drying kinetics, the effective moisture diffusivity, and the energy consumption of the two drying methods were evaluated respectively. It was found that the drying time was shortened from 22.0 min for convective drying to 16.0 min for microwave drying due to 27% of drying rate enhancement, and the effective moisture diffusivity was increased from 3.01×10-10 to 4.49×10-10 m2/s. Additionally, 88% of energy consumption could be saved in the microwave drying process. An artificial neural network (ANN) was employed to predict the moisture removing kinetics of MPP. The results revealed that the ANN modeling could be used to predict the drying kinetics of MPP effectively and then determine the moisture content in the drying process. © 2023 Korean Technical Assoc. of the Pulp and Paper Industry. All rights reserved.

The transport characteristics and kinetics of moisture in hot‐pressing are crucial to con-trolling the insulated paperboard drying process. The effects of operating temperature (110, 120, and 130 °C) on moisture transfer characteristics of an insulated paperboard were investigated. The results showed that the hot‐pressing process consists of four successive stages, i.e., the warm‐up stage, the boiling‐point temperature stabilization stage, the temperature slowly rising stage, and the constant temperature stage. It was observed that a higher temperature mainly affected the medium and later stages of the hot‐pressing process. When the operating temperature increased from 110 to 130 °C, the maximum value of the drying rate increased by 16.04%, and the drying time decreased by 62.50% consequently. Furthermore, a new mathematical model used to describe the moisture transfer kinetics for the insulated paperboard hot‐pressing was developed in this paper. The results from the proposed new model were evaluated with another eight commonly used models. It showed better predictions and satisfactorily described the moisture transfer kinetics of the insulated paperboard compared with other models under the investigated hot‐pressing conditions. The val-ues of R2, χ2, and root mean square error (RMSE) of the new model varied from 0.99961 to 0.99999, 0.00001 to 0.00005, and 0.00120 to 0.00599, respectively. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

The product could not be effectively expanded and the puffing temperature was too high, which usually occurred during the explosion puffing drying process of fruits and vegetables. CO2 high-pressure and low-temperature explosion puffing drying technology was investigated as potential means for the production of apple snack food. The samples were pre-dried with hot air to a moisture content of 15% to 20% (w.b.). The process factors including puffing pressure difference (0.86–1.54 MPa), puffing temperature (53–87 °C), and vacuum drying time (28–62 min) were investigated using response surface methodology with central composite design. The optimum CO2 high-pressure and low-temperature explosion puffing drying conditions were puffing pressure difference, puffing temperature, and vacuum drying time of 1.25 MPa, 74 °C, and 33 min, respectively. At this optimal condition, expansion ratio, rehydration ratio, and crispness were found to be 1.7, 2.23 g/g, and 29.3, respectively. Apple crisps obtained under optimal processing conditions have a highly porous structure from SEM micrographs. © 2020, © 2020 Taylor & Francis Group, LLC.

The drying characteristics of unbleached Kraft pulpboard have been studied in convective drying equipment under different hot air temperatures and velocities. In this work, the drying experiments were conducted in the range of 80-100 degrees C and 1.87-2.48m/s, respectively. The results indicated that high air temperature and velocity are beneficial to increasing drying rate and decreasing drying time. Ten thin-layer drying models were evaluated to describe the drying kinetic of unbleached Kraft pulpboard for its suitability. Based on the statistical analysis, the Yun model could predict the pulpboard drying kinetic better than others in terms of fitting performance. Through calculation and fitting, the effective moisture diffusivity varied from 2.077. 10-10 to 3.631. 10-10m(2)/s over the investigated temperature range and the average activation energy for moisture diffusion was 22.818kJ/mol.