1. What is the Evaporation Rate Formula?

The evaporation rate formula calculates the mass transfer rate of water evaporating into air. It's based on the difference between water vapor pressure and air vapor pressure, the surface area, and a mass transfer coefficient.

2. How Does the Calculator Work?

The calculator uses the evaporation rate equation:

Where:

• \( K \) — Mass transfer coefficient (kg/m²·s·Pa)
• \( A \) — Surface area (m²)
• \( P_w \) — Water vapor pressure (Pa)
• \( P_a \) — Air vapor pressure (Pa)

Explanation: The equation calculates the evaporation rate based on the driving force (vapor pressure difference) and the efficiency of mass transfer (coefficient K).

3. Importance of Evaporation Rate Calculation

Details: Calculating evaporation rates is crucial for designing cooling systems, predicting water loss in reservoirs, industrial drying processes, and climate modeling.

4. Using the Calculator

Tips: Enter all values in consistent SI units. The mass transfer coefficient (K) depends on temperature, air velocity, and surface characteristics.

5. Frequently Asked Questions (FAQ)

Q1: What affects the mass transfer coefficient (K)?
A: K depends on temperature, air velocity, surface roughness, and the properties of the evaporating liquid.

Q2: How to determine vapor pressures?
A: Pw can be found from steam tables at water temperature. Pa is the partial pressure of water vapor in air, often calculated from relative humidity.

Q3: What are typical evaporation rates?
A: Rates vary widely but might range from 1×10⁻⁶ to 1×10⁻⁴ kg/s·m² under normal conditions.

Q4: Does this work for other liquids?
A: Yes, but K and vapor pressure values must be appropriate for the specific liquid.

Q5: What about wind effects?
A: Higher wind speeds increase K, leading to higher evaporation rates.