Specific Enthalpy of Water Vapor Calculator

Formula Used:

\[ \text{Enthalpy of Dry Air} = 2500 + 1.9 \times \text{Dry Bulb Temperature in °C} \] \[ h_{dry} = 2500 + 1.9 \times t_{db} \]

Enthalpy of Dry Air:

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1. What is Specific Enthalpy of Water Vapor?

The specific enthalpy of water vapor represents the total heat content per unit mass of dry air, including both sensible and latent heat components. It's a crucial thermodynamic property in psychrometric calculations and HVAC system design.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ h_{dry} = 2500 + 1.9 \times t_{db} \]

Where:

\( h_{dry} \) — Enthalpy of dry air (kJ/kg)
\( t_{db} \) — Dry bulb temperature in °C

Explanation: The formula calculates the specific enthalpy based on the dry bulb temperature, where 2500 represents the latent heat component and 1.9 represents the specific heat capacity of water vapor.

3. Importance of Enthalpy Calculation

Details: Accurate enthalpy calculation is essential for determining the energy content of moist air, which is critical for HVAC system design, air conditioning load calculations, and psychrometric process analysis.

4. Using the Calculator

Tips: Enter the dry bulb temperature in degrees Celsius. The value must be valid (temperature ≥ -273.15°C, which is absolute zero).

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of the 2500 constant?
A: The 2500 kJ/kg represents the latent heat of vaporization of water at 0°C, which is the energy required to change water from liquid to vapor phase.

Q2: Why is the specific heat capacity 1.9 kJ/kg·°C?
A: This value represents the average specific heat capacity of water vapor over typical atmospheric temperature ranges used in HVAC calculations.

Q3: How does this relate to total enthalpy of moist air?
A: This calculation provides the enthalpy of dry air component. The total enthalpy of moist air would include additional terms for the moisture content.

Q4: What are typical enthalpy values for atmospheric air?
A: Typical values range from approximately 20-100 kJ/kg for most comfort conditioning applications, depending on temperature and humidity levels.

Q5: Are there limitations to this simplified formula?
A: This formula provides an approximation. For precise calculations, more comprehensive psychrometric equations that account for specific humidity should be used.