1. What is the Thermodynamic Equation?

The thermodynamic equation h = u + p v relates enthalpy (h) to internal energy (u), pressure (p), and specific volume (v). It's fundamental in thermodynamics for calculating properties of water and other substances.

2. How Does the Calculator Work?

The calculator uses the thermodynamic equation:

Where:

• \( h \) — Enthalpy (J/kg)
• \( u \) — Internal energy (J/kg)
• \( p \) — Pressure (Pa)
• \( v \) — Specific volume (m³/kg)

Explanation: The equation shows that enthalpy equals internal energy plus the product of pressure and specific volume.

3. Importance of Thermodynamic Calculations

Details: These calculations are crucial for designing thermal systems, analyzing energy transfers, and understanding phase changes in water and other working fluids.

4. Using the Calculator

Tips: Enter internal energy in J/kg, pressure in Pa, and specific volume in m³/kg. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is enthalpy used for?
A: Enthalpy is used to calculate heat transfer in open systems and is fundamental in analyzing turbines, compressors, and heat exchangers.

Q2: What are typical values for water?
A: For liquid water at 25°C: u ≈ 104.9 kJ/kg, p ≈ 101325 Pa, v ≈ 0.001 m³/kg, giving h ≈ 104.9 + 101.325 ≈ 206.225 kJ/kg.

Q3: Does this work for all substances?
A: The equation is general, but specific values of u, p, and v depend on the substance and its state (liquid, vapor, etc.).

Q4: What about phase changes?
A: During phase changes, internal energy and specific volume change significantly while pressure may remain constant.

Q5: How accurate is this calculation?
A: The calculation is mathematically exact, but accuracy depends on the precision of your input values.