Stack-wide effects in the modeling of solar kilns for drying timber

This study examines the stack-wide effects due to the humidification and co oling of air as it passes through a 6 m wide stack of Australian ironbark t imber for conditions that are representative of those for solar drying (dry and wet-bulb temperatures of 60 and 50 degreesC, respectively). A solar ki ln model-for a greenhouse-type design has been modified to account for the drying of timber boards and the possibility of stack-wide effects, in terms of moisture content differences in the streamwise direction of air flow th rough the stack. The maximum difference between the moisture contents of th e leading and trailing boards is Predicted to be 0.011 kg kg(-1) for these conditions, compared with timber moisture contents of 0.15-0.35 kg kg(-1). Hence, the stack-wide effect is insignificant for these conditions in this greenhouse kiln design and may be ignored, reducing the simulation time by over 50%. In addition, 14 elements within a finite-difference model for the drying of the,timber boards (25 mm thick) gives predictions of the drying time that are acceptably accurate, while minimizing the computational time.