Q60
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)
A.
M (Xo - XF)
AnswerB.
M (Xo/XF)
C.
M ln(Xo/XF)
D.
MXo ln(Xo/XF)
Answer: Option A
Solution
Answer: Option A
Solution:
Given:Drying occurs in the linear drying rate regime
Initial moisture content = Xo
Final moisture content = XF
Critical moisture content = Xo (same as initial moisture)
Drying rate becomes zero at X = 0
This implies that the entire drying happens in the constant (linear) rate period, because the critical moisture content is equal to the initial moisture content.
In the linear drying regime, the drying time (θ) is given by:
θ = (L / A Rc) × (Xo - XF)
Let M = L / A Rc
Therefore,
θ = M (Xo - XF)
Hence, the correct answer is:
Option A: M (Xo - XF)