Dynamic moisture sorption and humidity response inside the wooden space to cyclical changing external relative humidity

Wood is usually processed into various spaces and used in buildings, packaging and furniture. Dynamic moisture sorption and humidity response inside wooden space to sinusoidally changing external relative humidity (RH) were demonstrated by using a self-assembly device, which simultaneously recorded moisture content (MC) and RH changes. Wood has hierarchical structures, which provided the basis of moisture sorption and further influenced RH inside. Internal RH changed sinusoidally, similar to external RH and MC. During internal and external moisture exchange, water molecules experienced dynamic compound actions, including moisture gradient pressure, the attraction of sorption sites and water molecules and diffusing hindrance. Consequently, MC and internal RH exhibited dynamic phase lag of over 0.39 radian. Meanwhile, moisture sorption was higher for thinner wood, especially in a longer cyclic period since more water molecules interacted with sorption sites with less diffusing hindrance. Correspondingly, the humidity change was lower inside thicker wooden spaces in a shorter period. The average internal RH and amplitude decreased by 5% and 83.7%, respectively. Dynamic humidity change hysteresis existed and showed positive relation to the cyclic period but inversely with wood thickness. The study helped better understand dynamic moisture sorption and humidity change in wooden space and facilitated the better application of wood in human life.