ANS:B - more than

Flooding in a vapor-liquid contacting equipment occurs in a tray when the pressure drop through a tray is more than the liquid head available in the downcomer. Here's why:

• Flooding in a tray column occurs when the liquid flow rate exceeds the capacity of the tray to handle the liquid flow. This leads to the accumulation of liquid on the tray, impeding the passage of vapor through the tray and reducing the effectiveness of mass transfer.
• The liquid head available in the downcomer represents the height difference between the liquid level on the tray and the outlet of the downcomer. It provides the driving force for liquid flow from one tray to the next.
• If the pressure drop through a tray (which includes the resistance to vapor flow, liquid flow, and any other obstructions) exceeds the available liquid head in the downcomer, it means that the tray cannot accommodate the liquid flow rate, leading to flooding.
• Therefore, flooding occurs when the pressure drop through a tray is more than the liquid head available in the downcomer.