A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids))_____________?
Correct answer: D. MXo ln(Xo/XF)
- A. M(Xo - XF)
- B. M(Xo/XF)
- C. M ln(Xo/XF)
- D. MXo ln(Xo/XF)
Explanation
With the critical moisture equal to Xo, the falling-rate drying rate is Rc(X/Xo). Integrating dt = M dX/[Rc(X/Xo)] from Xo to XF gives t = M Xo ln(Xo/XF), so option d follows.
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