1. What is the Evaporation Rate Formula?

The evaporation rate formula calculates the mass transfer rate of a liquid evaporating into a gas. It's based on the pressure difference, temperature, diffusion characteristics, and physical dimensions of the system.

2. How Does the Calculator Work?

The calculator uses the evaporation rate equation:

Where:

• \( E \) — Evaporation rate (kg/s)
• \( \Delta P \) — Pressure difference between vapor and ambient (Pa)
• \( R \) — Universal gas constant (8.314 J/mol·K)
• \( T \) — Absolute temperature (K)
• \( D \) — Diffusion coefficient (m²/s)
• \( A \) — Surface area (m²)
• \( \delta \) — Boundary layer thickness (m)

Explanation: The equation accounts for the driving force (pressure difference), thermal effects, and mass transfer characteristics of the system.

3. Importance of Evaporation Rate Calculation

Details: Calculating evaporation rates is crucial for designing distillation systems, predicting environmental water loss, industrial drying processes, and chemical engineering applications.

4. Using the Calculator

Tips: Enter all values in SI units. Typical values: R = 8.314 J/mol·K, room temperature = 298.15 K. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What affects the diffusion coefficient (D)?
A: D depends on the liquid-gas pair, temperature, and pressure. It typically ranges from 10⁻⁵ to 10⁻⁴ m²/s for common substances.

Q2: How to estimate boundary layer thickness?
A: δ depends on flow conditions. For still air, it's typically 1-10 mm. For forced convection, it can be much smaller.

Q3: What's a typical evaporation rate?
A: Rates vary widely but often fall in the range of 10⁻⁶ to 10⁻⁴ kg/s for small-scale applications.

Q4: When is this formula not applicable?
A: Not valid for boiling conditions, high vacuum, or when chemical reactions occur at the surface.

Q5: How does temperature affect evaporation?
A: Higher temperature increases ΔP and D, typically leading to exponential increase in evaporation rate.