Partial Pressure Of Water Vapor In Air Calculator

Formula Used:

\[ P_{\infty} = P_w - \frac{h_{Conv} \times (T_{\infty} - T_w)}{h_{fg} \times k_L} \]

Partial Pressure (Pw):

Convective Heat Transfer Coefficient (hConv):

W/m²·K

Air Temperature (T∞):

°C

Wet Bulb Temperature (Tw):

°C

Enthalpy of Evaporation (hfg):

J/kg·K

Convective Mass Transfer Coefficient (kL):

m/s

Partial Pressure in Air (P∞):

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1. What is Partial Pressure of Water Vapor in Air?

Partial pressure in air of the water vapor is the pressure of water in the mixture of water and air. It represents the contribution of water vapor to the total pressure of the air-water vapor mixture.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ P_{\infty} = P_w - \frac{h_{Conv} \times (T_{\infty} - T_w)}{h_{fg} \times k_L} \]

Where:

\( P_{\infty} \) — Partial pressure in air of water vapor (Pa)
\( P_w \) — Partial pressure of water vapor at wet bulb temperature (Pa)
\( h_{Conv} \) — Convective heat transfer coefficient (W/m²·K)
\( T_{\infty} \) — Air temperature (°C)
\( T_w \) — Wet bulb temperature (°C)
\( h_{fg} \) — Enthalpy of evaporation (J/kg·K)
\( k_L \) — Convective mass transfer coefficient (m/s)

Explanation: This formula calculates the partial pressure of water vapor in air by accounting for the convective heat and mass transfer processes between the air and water vapor.

3. Importance of Partial Pressure Calculation

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

4. Using the Calculator

Tips: Enter all required values with appropriate units. Ensure all input values are positive and within reasonable physical ranges for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of partial pressure in air?
A: Partial pressure determines the concentration of water vapor in air and affects various properties like humidity, dew point, and heat transfer rates.

Q2: How does temperature difference affect the result?
A: A larger temperature difference between air and wet bulb increases the convective heat transfer, which affects the partial pressure calculation.

Q3: What are typical values for convective coefficients?
A: Convective heat transfer coefficients typically range from 5-25 W/m²·K for natural convection and 25-250 W/m²·K for forced convection.

Q4: Why is enthalpy of evaporation important?
A: Enthalpy of evaporation represents the energy required for phase change and significantly influences the heat and mass transfer calculations.

Q5: What applications use this calculation?
A: This calculation is used in HVAC design, drying processes, meteorological studies, and any application involving air-water vapor mixtures.