The minimum fluidization height of 1.20 m is maintained during fluidized bed drying of carrots. The bed diameter of the fluidized bed dryer is 0.6 m. If mass and solid density of carrots are 250 kg and 1040 kg m⁻³, respectively, then the porosity of the bed at the minimum fluidization condition is ____________ (rounded off to 3 decimal places, Consider π = 3.14).
Official Answer Key:
0.290 to 0.296
Step-by-Step Solution & Explanation
Bed (bulk) volume at minimum fluidization, V_bed = (π/4)D²×H = (3.14/4)×0.6²×1.20 = 0.7854×0.36×1.20 = 0.3391 m³.
Volume actually occupied by solids, V_solid = mass/density = 250/1040 = 0.2404 m³.
Porosity, ε = 1 − V_solid/V_bed = 1 − 0.2404/0.3391 = 1−0.7088 = 0.291. Within official range 0.290–0.296.
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