Effects of Ultrasound on Mass Transfer within the Boundary Layer during Wood Vacuum Drying
Zhengbin He,
Zhenyu Wang,
Huan Lv,
Zhenyu Zhang,
Songlin Yi
Affiliations
Zhengbin He
Beijing Forestry University; China
Zhenyu Wang
Beijing Key Laboratory of Wood Science and Engineering, MOE Key Laboratory of Wooden Material Science and Application, College of Material Science and Technology, Beijing Forestry University; China
Huan Lv
Beijing Key Laboratory of Wood Science and Engineering, MOE Key Laboratory of Wooden Material Science and Application, College of Material Science and Technology, Beijing Forestry University; China
Zhenyu Zhang
Beijing Key Laboratory of Wood Science and Engineering, MOE Key Laboratory of Wooden Material Science and Application, College of Material Science and Technology, Beijing Forestry University; China
Songlin Yi
Beijing Key Laboratory of Wood Science and Engineering, MOE Key Laboratory of Wooden Material Science and Application, College of Material Science and Technology, Beijing Forestry University; China
Ultrasound was applied to enhance mass transfer within the boundary layer during wood vacuum drying. Fast growing poplar (Populus tomentosa) was used as the specimen in this work. The water migration rates and the mass transfer coefficients were studied at temperatures of 35 and 50 °C, absolute pressures of 0.03, 0.06, and 0.1 MPa, and ultrasound power-frequency groups of 60 W-28 kHz, 100 W-28 kHz, and 100 W-20 kHz, respectively. The results indicated that ultrasound could markedly increase the water migration rates within the boundary layer. The water migration rates increased with increasing ultrasound power and frequency. The mass transfer coefficients within the boundary layer for specimens treated with ultrasound were much higher than those of the control group, and the mass transfer coefficients increased with decreasing absolute pressure. Ultrasound could be applied in the wood drying industry as a means of saving time and energy.
