A wet, clay brick measuring 2 × 4 × 6 in. has an initial uniform moisture content of 12 wt%..At time = 0, the brick is exposed on all sides to .air such that the surface moisture content is maintained at 2 wt%. After 5 h, the average moisture content is 8 wt%. Estimate:
(a) The diffusivity of water in the clay in cm2/s.
(b) The additional time for the average moisture content to reach 4 wt%. All moisture contents are on a dry basis.