1. What is the D² Law for Water Droplet Evaporation?

The D² law describes the evaporation rate of liquid droplets, stating that the square of the droplet diameter decreases linearly with time. This fundamental principle is widely used in combustion, spray drying, and atmospheric science to model droplet evaporation behavior.

2. How Does the Calculator Work?

The calculator uses the D² law equation:

Where:

• \( d \) — Current droplet diameter (meters)
• \( d₀ \) — Initial droplet diameter (meters)
• \( K \) — Evaporation constant (m²/s)
• \( t \) — Time elapsed (seconds)

Explanation: The equation shows that the surface area-related evaporation causes the diameter squared to decrease linearly over time, with K representing the evaporation rate constant that depends on environmental conditions.

3. Importance of Droplet Evaporation Calculation

Details: Accurate droplet evaporation calculations are essential for designing spray systems, predicting fuel combustion efficiency, modeling atmospheric processes, and optimizing industrial drying operations. The D² law provides a fundamental framework for understanding mass transfer in droplet systems.

4. Using the Calculator

Tips: Enter initial droplet diameter in meters, evaporation constant in m²/s, and time in seconds. Typical K values range from 10⁻¹¹ to 10⁻⁸ m²/s depending on temperature, humidity, and droplet composition.

5. Frequently Asked Questions (FAQ)

Q1: What factors affect the evaporation constant K?
A: K depends on temperature, relative humidity, air velocity, droplet composition, and atmospheric pressure. Higher temperatures and lower humidity increase K values.

Q2: Is the D² law valid for all droplet sizes?
A: The D² law works well for droplets larger than 10 microns. For smaller droplets, non-continuum effects and other factors may cause deviations.

Q3: How is the evaporation constant determined experimentally?
A: K is typically measured by tracking droplet diameter changes over time using high-speed imaging or laser diffraction techniques under controlled conditions.

Q4: Does the D² law apply to non-water droplets?
A: Yes, the D² law applies to various liquids, but the evaporation constant K will differ based on the liquid's vapor pressure, diffusion coefficient, and other properties.

Q5: What happens when d² becomes negative in the calculation?
A: A negative d² value indicates the droplet has completely evaporated before the specified time. The calculator shows d = 0 meters in this case.