Contents

Stagnation enthalpy

${\displaystyle h_{0}=h+{\frac {V^{2}}{2}}}$

where:

${\displaystyle h_{0}=}$ mass-specific total enthalpy, in [J/kg]

${\displaystyle h=}$ mass-specific static enthalpy, in [J/kg]

${\displaystyle V=}$ fluid velocity at the point of interest, in [m/s]

${\displaystyle {\frac {V^{2}}{2}}=}$ mass-specific kinetic energy, in [J/kg]

The volume-specific version of this equation (in units of energy per volume, [J/m^3] is obtained by multiplying the equation with the fluid density ${\displaystyle \rho }$:

${\displaystyle h_{0}^{*}=h^{*}+\rho {\frac {V^{2}}{2}}}$

where:

${\displaystyle h_{0}^{*}=}$ volume-specific total enthalpy, in [J/m^3]

${\displaystyle h^{*}=}$ volume-specific static enthalpy, in [J/m^3]

${\displaystyle V=}$ fluid velocity at the point of interest, in [m/s]

${\displaystyle \rho =}$ fluid density at the point of interest, in [kg/m^3]

${\displaystyle \rho {\frac {V^{2}}{2}}=}$ volume-specific kinetic energy, in [J/m^3]

The non-specific version of this equation, that means extensive quantities are used, is:

${\displaystyle H_{0}=H+m{\frac {V^{2}}{2}}}$

where:

${\displaystyle H_{0}=}$ total enthalpy, in [J]

${\displaystyle H=}$ static enthalpy, in [J]

${\displaystyle m=}$ fluid mass, in [kg]

${\displaystyle V=}$ fluid velocity at the point of interest, in [m/s]

${\displaystyle m{\frac {V^{2}}{2}}=}$ kinetic energy, in [J]

The suffix ‘0’ usually denotes the stagnation condition and is used as such here.^[1][3]

Enthalpy is the energy associated with the temperature plus the energy associated with the pressure. The stagnation enthalpy adds a term associated with the kinetic energy of the fluid mass.^[2]

The total enthalpy for a real or ideal gas does not change across a shock. The total enthalpy can not be measured directly. Instead, the static enthalpy and the fluid velocity can be measured. Static enthalpy is often used in the energy equation for a fluid.

• Stagnation pressure
• Stagnation temperature
• Rothalpy

http://ocw.mit.edu/ans7870/16/16.unified/thermoF03/chapter_6.htm