Amount of heat released per unit volume when it undergoes oxidation at normal pressure and temperature (0.1 MPa and 298 K).
Lower heating value (LHV) – amount of heat released by burning 1 kg of fuel assuming the latent heat of vaporization in the reaction products is not recovered.
Higher heating value (HHV) – heating value of the fuel when water is condensed.
is the Latent heat of vaporization of water at 298.15 K
is the Latent heat of vaporization of water at 298.15 K 
