Heat Transfer Characteristics during Superheated Steam Vacuum Drying of Poplar

Superheated steam vacuum drying shows major advantages in terms of reducing the boiling point of water and speeding up the drying process, but to our knowledge, no researcher has addressed the effects of drying conditions on heat transfer characteristics during superheated steam vacuum drying of wood. In this study, we did so using fast-growing poplar. Temperatures inside the wood were measured and the convective heat transfer coefficients calculated under temperature conditions of 35 degrees C, 55 degrees C, and 70 degrees C and absolute pressures of 0.03, 0.06, and 0.1 MPa. The results of our subsequent analysis showed that the ultimate temperatures inside wood increase alongside increasing absolute pressure at the set temperature conditions and are lower than that of the drying medium. In addition, we found that convective heat transfer coefficients increase as absolute pressure increases at the set temperatures and also increase as temperature increases at set absolute pressure conditions. We then established a convective heat transfer coefficient model based on the experimental results. The findings presented here may provide theoretical guidance for maximizing the available advantages of superheated steam vacuum drying and choosing appropriate drying schedules for poplar in future applications.