Q1: For flow of fluids through packed bed, the superficial velocity is

ANS:A - less than the average velocity through channels.

For the flow of fluids through a packed bed, the superficial velocity is more than the average velocity through channels.

Explanation:

1. Superficial Velocity:
   • Superficial velocity (vsv_svs​) is defined as the flow rate of the fluid per unit cross-sectional area of the entire pipe or packed bed. It considers the total cross-sectional area available for flow, including both the open spaces (voids) and the solid particles (bed material).
2. Average Velocity Through Channels:
   • The average velocity through channels refers to the velocity of the fluid only through the open spaces (voids) between the solid particles in the packed bed.
   • This average velocity (vavgv_{avg}vavg​) is generally lower than the superficial velocity because it considers only the effective cross-sectional area available for fluid flow (voids).
3. Comparison:
   • Superficial velocity (vsv_svs​) is higher than the average velocity through channels (vavgv_{avg}vavg​) because it accounts for the entire cross-sectional area, including both voids and solid particles.
   • In a packed bed, the fluid flows through both the void spaces and around the solid particles, resulting in a higher superficial velocity compared to the average velocity through the channels (voids).
4. Pressure Drop Dependency:
   • The superficial velocity is not directly dependent on the pressure drop across the bed but rather on the total flow rate and the cross-sectional area of the bed.

Conclusion: