Subtopic: Fluidization of granular solids – pneumatic, bucket, screw and belt conveying
Question Statement:
Which of the following parameters appear in Ergun's equation for predicting the pressure drop and minimum fluidization velocity ($u_{mf}$) through a bed of granular agricultural grains?
Options:
(A) Bed voidage (porosity $\varepsilon$) at minimum fluidization
(B) Particle sphericity ($\phi_s$) and equivalent spherical diameter ($d_p$)
(C) Fluid density ($\rho$) and dynamic viscosity ($\mu$)
(D) Dielectric loss factor of the fluidizing gas
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
Ergun's equation combines viscous energy loss (Kozeny-Carman term $\propto \frac{\mu u (1-\varepsilon)^2}{\phi_s^2 d_p^2 \varepsilon^3}$) and kinetic energy loss (Burke-Plummer term $\propto \frac{\rho u^2 (1-\varepsilon)}{\phi_s d_p \varepsilon^3}$). Options A, B, and C are included. Dielectric loss factor (D) has no physical role in fluid mechanics.