Partial Pressure Of Water Vapor Calculator

Formula Used:

\[ p_v = p_w - \frac{(p_t - p_w) \times (T_{db} - T_w)}{1544 - 1.44 \times T_w} \]

Saturation Pressure Corresponding to WBT:

Total Pressure of Moist Air:

Dry Bulb Temperature:

°C

Wet Bulb Temperature:

°C

Pressure of Water Vapor:

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1. What is Partial Pressure of Water Vapor?

The partial pressure of water vapor is the pressure exerted by water vapor in a mixture of gases. It's a crucial parameter in psychrometrics and HVAC calculations, representing the contribution of water vapor to the total pressure of moist air.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ p_v = p_w - \frac{(p_t - p_w) \times (T_{db} - T_w)}{1544 - 1.44 \times T_w} \]

Where:

\( p_v \) — Pressure of Water Vapor (Pa)
\( p_w \) — Saturation Pressure Corresponding to WBT (Pa)
\( p_t \) — Total Pressure of Moist Air (Pa)
\( T_{db} \) — Dry Bulb Temperature (°C)
\( T_w \) — Wet Bulb Temperature (°C)

Explanation: This formula calculates the partial pressure of water vapor based on the relationship between dry bulb temperature, wet bulb temperature, and the saturation pressure at wet bulb temperature.

3. Importance of Water Vapor Pressure Calculation

Details: Accurate calculation of water vapor pressure is essential for humidity control, air conditioning design, meteorological studies, and various industrial processes involving air-water vapor mixtures.

4. Using the Calculator

Tips: Enter all values in the specified units. Saturation pressure and total pressure should be in Pascals (Pa), while temperatures should be in degrees Celsius (°C). Ensure all values are positive and valid.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between dry bulb and wet bulb temperature?
A: Dry bulb temperature is the air temperature measured by a regular thermometer. Wet bulb temperature is measured by a thermometer with a wet wick around its bulb and indicates the lowest temperature achievable through evaporative cooling.

Q2: How is saturation pressure corresponding to WBT determined?
A: Saturation pressure at wet bulb temperature can be found from steam tables or calculated using empirical formulas that relate temperature to vapor pressure.

Q3: What are typical values for water vapor pressure in atmospheric air?
A: Water vapor pressure in atmospheric air typically ranges from 0 to about 4 kPa, depending on temperature and humidity conditions.

Q4: Why is the denominator in the formula 1544 - 1.44*Tw?
A: This denominator represents an empirical relationship that accounts for the psychrometric constant and the specific heat of moist air, which varies with temperature.

Q5: Can this formula be used for high-temperature applications?
A: The formula is generally valid for typical atmospheric conditions. For high-temperature applications or extreme conditions, more specialized equations may be required.