Partial Pressure of Water Vapor Calculator

Partial Pressure Formula:

\[ P_w = \frac{RH}{100} \times P_{sat} \]

Partial Pressure (Pa):

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1. What is Partial Pressure of Water Vapor?

Definition: This calculator determines the partial pressure of water vapor in air based on relative humidity and saturation pressure.

Purpose: It's essential for HVAC design, meteorology, and industrial processes where moisture content in air needs to be quantified.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ P_w = \frac{RH}{100} \times P_{sat} \]

Where:

\( P_w \) — Partial pressure of water vapor (Pa)
\( RH \) — Relative humidity (%)
\( P_{sat} \) — Saturation vapor pressure (Pa)

Explanation: The relative humidity percentage is converted to a decimal fraction (divided by 100) and multiplied by the saturation pressure at the given temperature.

3. Importance of Partial Pressure Calculation

Details: Knowing the partial pressure helps determine dew point, predict condensation, and design proper ventilation systems.

4. Using the Calculator

Tips: Enter relative humidity (0-100%) and saturation pressure (must be > 0). The saturation pressure depends on temperature and can be found in thermodynamic tables.

5. Frequently Asked Questions (FAQ)

Q1: What is saturation pressure?
A: The maximum vapor pressure at a given temperature when air is saturated with water vapor.

Q2: How does temperature affect the calculation?
A: Temperature determines P_sat (higher temperature = higher saturation pressure).

Q3: What units should I use?
A: This calculator uses Pascals (Pa), but you can convert from other units before entering values.

Q4: Can RH be more than 100%?
A: No, the calculator limits RH to 0-100% as supersaturation is rare and temporary.

Q5: Where is this calculation used?
A: In meteorology, HVAC systems, industrial drying processes, and building science applications.