The impact of climate conditions on capillary mass flow and induced moisture content gradient was monitored during convective drying of beechwood (Fagus sylvatica L.). 6 mm, 12 mm, 18 mm, 24 mm radially oriented beechwood specimens were used. Series of conventional drying processes were carried out in a laboratory tunnel drier at constant drying temperature of 30 °C and constant relative humidity (RH) of 85 % with varying air velocity (h) from 0.6m/s to 2.1 m/s. During the drying, moisture content, moisture content gradient and water mass flow were gravimetrically determined at successive time intervals. Increasing the air velocity, the drying rate generally increased; increasing the thickness of wood the drying rate decreased. Increase of the air velocity shortened the period of initial constant drying rate, and eliminated it at greater material thicknesses. A high initial drying rate caused immediate irreversible reduction of initial water mass flow, and significantly prolonged the drying procedure.
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