Enthalpy of Moist Air Calculator

Enthalpy of Moist Air Equation:

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

Enthalpy of Moist Air:

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1. What is the Enthalpy of Moist Air?

The Enthalpy of Moist Air is the sum of the enthalpy of the dry air and the enthalpy of the water vapour. It represents the total heat content of moist air per unit mass and is a crucial parameter in HVAC and psychrometric calculations.

2. How Does the Calculator Work?

The calculator uses the Enthalpy of Moist Air equation:

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

Where:

\( h \) — Enthalpy of Moist Air (kJ/kg)
\( t_{db} \) — Dry Bulb Temperature in °C
\( \omega \) — Specific Humidity (kg/kg)

Explanation: The equation accounts for the sensible heat component (1.005×t_db) and the latent heat component (ω×(2500+1.9×t_db)) of moist air.

3. Importance of Enthalpy Calculation

Details: Accurate enthalpy calculation is essential for HVAC system design, air conditioning load calculations, psychrometric analysis, and energy efficiency assessments in building systems.

4. Using the Calculator

Tips: Enter dry bulb temperature in °C and specific humidity in kg/kg. Both values are required for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of the constants 1.005 and 1.9?
A: 1.005 kJ/kg·K is the specific heat of dry air at constant pressure, and 1.9 kJ/kg·K is the specific heat of water vapor at constant pressure.

Q2: Why is 2500 used in the equation?
A: 2500 kJ/kg represents the approximate latent heat of vaporization of water at 0°C, which is the energy required to change water from liquid to vapor phase.

Q3: What are typical enthalpy values for moist air?
A: Enthalpy values vary widely depending on temperature and humidity. At standard comfort conditions (25°C, 50% RH), enthalpy is typically around 50-55 kJ/kg.

Q4: How does enthalpy relate to human comfort?
A: Enthalpy is directly related to the total heat content of air, which affects both temperature perception and moisture comfort levels in occupied spaces.

Q5: Are there limitations to this equation?
A: This equation provides accurate results for most engineering applications, but for precise scientific calculations, more complex equations that account for variable specific heats may be required.