Wet Bulb Temperature Given Gas Constant Of Water Vapor Calculator

Formula Used:

\[ T_w = T_\infty - \frac{h_{fg} \cdot (P_w - P_\infty)}{R_w \cdot \rho \cdot c_p \cdot T_f \cdot Le^{0.67}} \]

Air Temperature (T∞):

°C

Enthalpy of Evaporation (hfg):

J/kg·K

Partial Pressure (Pw):

Partial Pressure in Air (P∞):

Gas Constant (Rw):

J/kg·K

Density (ρ):

kg/m³

Specific Heat of Air (cp):

J/kg·K

Mean Temperature (Tf):

°C

Lewis Number (Le):

Wet Bulb Temperature (Tw):

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1. What is Wet Bulb Temperature?

Wet bulb temperature is the lowest temperature that can be reached by the evaporation of water only. It represents the temperature read by a thermometer covered in water-soaked cloth over which air is passed.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ T_w = T_\infty - \frac{h_{fg} \cdot (P_w - P_\infty)}{R_w \cdot \rho \cdot c_p \cdot T_f \cdot Le^{0.67}} \]

Where:

\( T_w \) — Wet bulb temperature (°C)
\( T_\infty \) — Air temperature (°C)
\( h_{fg} \) — Enthalpy of evaporation (J/kg·K)
\( P_w \) — Partial pressure of water vapor at wet bulb temperature (Pa)
\( P_\infty \) — Partial pressure of water vapor in air (Pa)
\( R_w \) — Gas constant of water vapor (J/kg·K)
\( \rho \) — Density of air (kg/m³)
\( c_p \) — Specific heat of air (J/kg·K)
\( T_f \) — Mean temperature (°C)
\( Le \) — Lewis number (dimensionless)

Explanation: This formula calculates the wet bulb temperature by considering the energy balance between sensible heat and latent heat transfer during the evaporation process.

3. Importance of Wet Bulb Temperature Calculation

Details: Wet bulb temperature is crucial for understanding human comfort, heat stress assessment, HVAC system design, and various industrial processes involving evaporation and cooling.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between dry bulb and wet bulb temperature?
A: Dry bulb temperature is the ambient air temperature, while wet bulb temperature is the temperature measured by a thermometer covered with a wet cloth, indicating the cooling effect of evaporation.

Q2: Why is Lewis number important in this calculation?
A: The Lewis number relates heat and mass transfer coefficients and is crucial for accurate calculation of the wet bulb temperature.

Q3: What are typical values for the gas constant of water vapor?
A: The gas constant for water vapor is approximately 461.5 J/kg·K.

Q4: How does humidity affect wet bulb temperature?
A: Higher humidity reduces the evaporation rate, resulting in a wet bulb temperature closer to the dry bulb temperature.

Q5: What are practical applications of wet bulb temperature?
A: Applications include weather forecasting, HVAC design, industrial cooling processes, and assessing human heat stress conditions.