Chemistry:Heat release parameter

In combustion, heat release parameter (or gas expansion parameter) is a dimensionless parameter which measures the amount of heat released by the combustion process. It is defined as

$\alpha =\frac{T_b-T_u}{T_b}$

where

• $T_b$ is the burnt gas temperature
• $T_u$ is the unburnt mixture temperature.

In typical combustion process, $\alpha \approx 0.7-0.9$. For isobaric combustion, using ideal gas law, the parameter can be expressed in terms of density, i.e.,

$\alpha =\frac{T_b-T_u}{T_b}=\frac{{\rho }_u-{\rho }_b}{{\rho }_u}.$

The ratio of burnt gas to unburnt gas temperature is

$\frac{T_b}{T_u}=\frac{{\rho }_u}{{\rho }_b}=\frac{1}{1-\alpha }.$

See also

• Zel'dovich number