A packed cylindrical bed with a diameter of 0.5 m and height of 0.5 m contains uniform spherical particles of 1500 μm size and specific gravity 2.5, with an initial porosity of 0.4. Using Ergun’s equation expressed in SI units as Δ P/L = 375 × 103 VOM + 10.94 × 106 V2 OM, determine the minimum fluidization velocity VOM when water serves as the fluidizing fluid_________________?
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Answer: B. 16 mm/s
Explanation
Ergun equation balances viscous and kinetic energy losses against the buoyant weight of the packed bed. Solving the quadratic pressure drop equation for minimum fluidization velocity yields sixteen millimeters per second. Water properties and particle characteristics determine the exact fluid velocity required for incipient fluidization. Ergun equation is the fundamental mathematical model for predicting pressure drop in packed beds. Minimum fluidization velocity represents the superficial velocity where particles just begin to suspend. Bed porosity and particle sphericity are critical input parameters in fluidization calculations.
Designing fluidized bed reactors requires precise calculation of minimum fluidization velocities for gas-solid systems. Operating below minimum fluidization leaves beds packed while exceeding it causes particle entrainment. Water-fluidized systems find applications in ion exchange columns and biological wastewater treatment filters. Alternative velocity values fail to satisfy the balance between fluid drag and packed bed weight. Incorrect viscosity or density inputs lead to erroneous root solutions when solving Ergun quadratic formulas. Ignoring kinetic energy terms results in inaccurate minimum fluidization velocity predictions for liquid systems.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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