A flat slab of Douglas fir wood 50.8 mm thick containing 30 wt% moisture is bending dried from both sides (neglecting ends and edges). The equilibrium moisture content at the surface of the wood due to the drying air blown over it is held at 5 wt% moisture.

The drying can be assumed to be represented by a diffusivity of 3.72x10−6−6m22/h.

Calculate the time for the center to reach 10% moisture.