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Enthalpy

Enthalpy is a state property that combines internal energy with pressure and volume, and is especially useful for flow processes at constant pressure, such as in a turbine or heat exchanger. The change in enthalpy then corresponds directly to the heat added or removed.

H=U+pVH = U + pVenthalpy

Symbols

HHenthalpyJ
UUinternal energyJ
pppressurePa

Example

A gas has U=500U = 500 J, p=100p = 100 kPa and V=0.002V = 0.002 m³. The enthalpy is H=500+100.000⋅0.002=700H = 500 + 100.000\cdot 0.002 = 700 J.

At constant pressure, the enthalpy change equals the heat added: ΔH=Qp\Delta H = Q_p.
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Part of Thermodynamics: Heat and entropy.