1. What is Weep Point Velocity in Distillation?

Definition: Weep point velocity is the minimum vapor velocity through tray holes needed to prevent liquid from weeping through the holes in a distillation column tray.

Purpose: This calculation helps chemical engineers design distillation columns that operate efficiently without liquid weeping, which can reduce separation efficiency.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( u_h \) — Weep point vapor velocity (m/s)
• \( K_2 \) — Weep point correlation constant (typically 30 for sieve trays)
• \( d_h \) — Hole diameter (mm)
• \( \rho_v \) — Vapor density (kg/m³)

Explanation: The formula accounts for the balance between vapor momentum and liquid head that would otherwise cause weeping.

3. Importance of Weep Point Calculation

Details: Proper weep point velocity estimation ensures tray efficiency is maintained by preventing liquid from bypassing the active bubbling area of the tray.

4. Using the Calculator

Tips: Enter the weep point constant (default 30), hole diameter in mm (default 5mm), and vapor density in kg/m³ (default 1.71). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical value for K₂?
A: For sieve trays, K₂ is typically 30, but may vary for other tray types or specific operating conditions.

Q2: How does hole diameter affect weep point velocity?
A: Larger holes require lower weep point velocities as the liquid head pressure is less effective at pushing liquid through larger openings.

Q3: What happens if operating velocity is below weep point?
A: Liquid will weep through the tray holes, reducing contact between vapor and liquid, and decreasing separation efficiency.

Q4: How does vapor density affect the result?
A: Denser vapors require lower velocities to prevent weeping because they have greater momentum at the same velocity.

Q5: Is this formula valid for all tray types?
A: This formula is primarily for sieve trays. Valve trays and bubble caps have different weep characteristics.