1. What is Enthalpy?

Enthalpy is a thermodynamic quantity equivalent to the total heat content of a system. It is defined as the sum of the internal energy of the system plus the product of its pressure and volume.

2. How Does the Calculator Work?

The calculator uses the enthalpy formula:

Where:

• \( h \) — Enthalpy (J/kg)
• \( u \) — Internal Energy (J/kg)
• \( P \) — Pressure (Pa)
• \( v \) — Specific Volume (m³/kg)

Explanation: The formula calculates the total energy content of a system by combining the internal energy with the flow work component (P × v).

3. Importance of Enthalpy Calculation

Details: Enthalpy is a fundamental concept in thermodynamics used in various applications including heat transfer calculations, energy balance equations, and analysis of thermodynamic processes in engineering systems.

4. Using the Calculator

Tips: Enter internal energy in J/kg, pressure in Pa, and specific volume in m³/kg. All values must be valid (internal energy ≥ 0, pressure ≥ 0, specific volume > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between enthalpy and internal energy?
A: Enthalpy includes both the internal energy of a system and the energy required to make room for it by displacing its environment (P × v term).

Q2: In which applications is enthalpy commonly used?
A: Enthalpy is widely used in heat exchanger design, refrigeration cycles, power plant analysis, and chemical process calculations.

Q3: What are typical units for enthalpy?
A: Enthalpy is typically measured in joules per kilogram (J/kg) in the SI system, or BTU per pound in the imperial system.

Q4: How does specific volume relate to density?
A: Specific volume is the reciprocal of density (v = 1/ρ), representing the volume occupied by a unit mass of a substance.

Q5: Can this formula be used for all thermodynamic systems?
A: This fundamental definition applies to all systems, though for ideal gases and other specific substances, enthalpy can be expressed in terms of temperature and specific heat capacities.