Radio frequency-assisted drying of wood: a comprehensive review

Drying is one of the most important steps in wood utilization. Several methods are followed to dry wood and kiln drying is mainly used at industrial scale. However, conventional kiln drying is very energy and time intensive. Radio frequency (RF) heating offers certain advantages over conventional heating. The research on RF-based wood drying was initiated in the 1960s and a number of studies have been carried out on various aspects of RF drying. However, a systematic review of RF-based wood drying is still lacking. This review attempts to examine the research and application of RF in wood drying. It presents a brief introduction to the importance of wood-drying followed by the application of RF in drying wood. It explores how RF heating aids in faster drying with minimum drying degrade. Additionally, it highlights the possibilities of combining RF heating with other methods. Emphasis is laid on other related aspects such as dielectric properties of wood, modelling of the drying process under RF heating, the effect of pre-treatments on drying characteristics of wood and comparison of properties of wood dried using various methods. Based on the review, some insights on future work have been suggested to increase the adaptability of RF heating-based wood drying.