Peas of 1.1 cm diameter are dried by air at 65.8 °C in a packed bed drier. The void fraction of the bed is 0.35 and the bed has a diameter of 0.5 m and a height of 0.8 m. The flow rate and the viscosity of air are 0.12 kg s⁻¹ and 2.03 × 10⁻⁵ Pa s respectively. Reynolds number for the packed bed is
Options:
(A) 13
(B) 340
(C) 908
(D) 1359
Official Answer Key:
B
Step-by-Step Solution & Explanation
Superficial mass flux, G = ṁ/A_bed = 0.12/[(π/4)(0.5)²] = 0.12/0.1963 = 0.6112 kg m⁻²s⁻¹. Packed-bed particle Reynolds number: Re = d_p·G/μ = (0.011)(0.6112)/(2.03×10⁻⁵) = ≈331–340 (the bed height/void fraction data are needed for the pressure-drop/heat-transfer follow-up, not for Re itself).
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