Partial Pressure Of Vapor Given Vapor Density Calculator

Formula Used:

\[ p_v = p_t - \frac{\rho_v \times 287 \times t_d}{\omega} \]

Total Pressure of Moist Air (p_t):

Vapor Density (ρ_v):

kg/m³

Dry Bulb Temperature (t_d):

Specific Humidity (ω):

Pressure of Water Vapor (p_v):

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1. What is Partial Pressure of Water Vapor?

The partial pressure of water vapor is the pressure exerted by the water vapour in moist air or a mixture of dry air and water vapour. It represents the contribution of water vapor to the total pressure of the air mixture.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ p_v = p_t - \frac{\rho_v \times 287 \times t_d}{\omega} \]

Where:

\( p_v \) — Pressure of water vapor (Pa)
\( p_t \) — Total pressure of moist air (Pa)
\( \rho_v \) — Vapor density (kg/m³)
\( t_d \) — Dry bulb temperature (K)
\( \omega \) — Specific humidity
287 — Gas constant for dry air (J/kg·K)

Explanation: This formula calculates the partial pressure of water vapor by subtracting the pressure contribution of dry air from the total pressure of the moist air mixture.

3. Importance of Partial Pressure Calculation

Details: Calculating partial pressure of water vapor is crucial for understanding humidity levels, psychrometric processes, HVAC system design, and various industrial applications involving air-water vapor mixtures.

4. Using the Calculator

Tips: Enter total pressure in Pascals, vapor density in kg/m³, dry bulb temperature in Kelvin, and specific humidity (dimensionless). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between partial pressure and humidity?
A: Partial pressure of water vapor is directly related to absolute humidity and affects relative humidity calculations in psychrometrics.

Q2: Why is 287 used in the formula?
A: 287 J/kg·K is the specific gas constant for dry air, which is used to calculate the pressure contribution of dry air in the mixture.

Q3: What are typical values for vapor density?
A: Vapor density typically ranges from 0 to about 0.03 kg/m³ in atmospheric conditions, depending on temperature and humidity.

Q4: How does temperature affect partial pressure?
A: Higher temperatures generally allow air to hold more moisture, potentially increasing the partial pressure of water vapor.

Q5: What are common applications of this calculation?
A: This calculation is used in HVAC design, meteorology, industrial drying processes, and environmental control systems.