Specific Humidity Given Enthalpy Of Moist Air Calculator

Specific Humidity Formula:

\[ \omega = \frac{(h - 1.005 \times t_{db})}{(2500 + 1.9 \times t_{db})} \]

Specific Humidity (ω):

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1. What is Specific Humidity?

Specific Humidity is the ratio of the mass of water vapor to the total mass of the air parcel. It provides an accurate measure of the moisture content in air, independent of temperature changes.

2. How Does the Calculator Work?

The calculator uses the Specific Humidity formula:

\[ \omega = \frac{(h - 1.005 \times t_{db})}{(2500 + 1.9 \times t_{db})} \]

Where:

\( \omega \) — Specific Humidity (kg/kg)
\( h \) — Enthalpy of Moist Air (kJ/kg)
\( t_{db} \) — Dry Bulb Temperature (°C)
1.005 — Specific heat of dry air (kJ/kg·K)
2500 — Latent heat of vaporization (kJ/kg)
1.9 — Specific heat of water vapor (kJ/kg·K)

Explanation: The formula calculates specific humidity by relating the enthalpy of moist air to the dry bulb temperature and known thermodynamic properties of air and water vapor.

3. Importance of Specific Humidity Calculation

Details: Accurate specific humidity calculation is crucial for HVAC system design, meteorological studies, industrial processes, and environmental control systems where precise moisture content measurement is essential.

4. Using the Calculator

Tips: Enter enthalpy of moist air in kJ/kg and dry bulb temperature in °C. Ensure both values are valid and within reasonable physical ranges for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between specific humidity and relative humidity?
A: Specific humidity measures the actual mass of water vapor per mass of air, while relative humidity measures how close the air is to saturation at a given temperature.

Q2: What are typical specific humidity values?
A: Specific humidity typically ranges from 0.0001 kg/kg in dry air to 0.03 kg/kg in very humid tropical conditions.

Q3: Why is specific humidity important in HVAC systems?
A: Specific humidity helps determine the amount of moisture that needs to be added or removed from air for proper humidity control in building environments.

Q4: How does temperature affect specific humidity?
A: Specific humidity remains constant with temperature changes unless moisture is added or removed, making it a conservative property for air mass tracking.

Q5: What are the limitations of this calculation?
A: This formula assumes standard atmospheric conditions and may have reduced accuracy at extreme temperatures or pressures outside normal ranges.