Mass Transfer - Study Mode
[#476] A solid is being dried in the linear drying rate regime from moisture content X o to X F . The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture X o . The drying time for M = (L s /AR c ) is (where, L = total mass of dry solid, A = total surface area for drying R c = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)
Correct Answer
(A) M (X o - X F )
Explanation
Solution: Given: Drying occurs in the linear drying rate regime Initial moisture content = X o Final moisture content = X F Critical moisture content = X o (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 R c ) × (X o - X F ) Let M = L / A R c Therefore, θ = M (X o - X F ) Hence, the correct answer is: Option A: M (X o - X F )
[#477] Mass transfer co-efficient is directly proportional to D AB 0.5 , according to __________ theory.
Correct Answer
(A) Penetration
[#478] Which of the following provides maximum contact surface for a liquid-vapour system?
Correct Answer
(A) Packed tower
[#479] In distillation where q is defined as the moles of liquid flow in the stripping section per mole of feed introduced, for saturated liquid feed
Correct Answer
(C) q = 1
[#480] A slurry is to be dried to produce flaky solid. Which dryer would you recommend?
Correct Answer
(A) Spray dryer