1. What is Water Vapor Pressure?

Water vapor pressure is the pressure exerted by water vapor in equilibrium with liquid water at a given temperature. It's a fundamental parameter in meteorology, HVAC design, and industrial processes.

2. How Does the Calculator Work?

The calculator uses the Magnus formula:

Where:

• \( e_w \) — Water vapor pressure (hPa)
• \( T \) — Temperature (°C)
• \( \exp \) — Exponential function

Explanation: This empirical formula approximates the relationship between temperature and the saturation vapor pressure of water.

3. Importance of Water Vapor Pressure

Details: Water vapor pressure is essential for calculating humidity parameters, predicting weather patterns, designing ventilation systems, and understanding evaporation processes.

4. Using the Calculator

Tips: Enter temperature in degrees Celsius. The formula is valid for temperatures between -45°C and 60°C for most practical purposes.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between vapor pressure and saturation vapor pressure?
A: Saturation vapor pressure is the maximum vapor pressure possible at a given temperature, while actual vapor pressure depends on the amount of water vapor present.

Q2: How does vapor pressure relate to relative humidity?
A: Relative humidity = (actual vapor pressure / saturation vapor pressure) × 100%.

Q3: Why does vapor pressure increase with temperature?
A: Higher temperatures increase water molecule energy, allowing more molecules to escape the liquid phase and enter the vapor phase.

Q4: What are typical vapor pressure values?
A: At 20°C it's about 23.4 hPa, at 30°C about 42.4 hPa, and at 0°C about 6.1 hPa.

Q5: Are there more accurate formulas?
A: Yes, the August-Roche-Magnus formula is more accurate but more complex. The simplified version shown here is sufficient for most applications.