Differentiating the Physical Optimum from the Exergetic Evaluation of a Methane Combustion Process

Combustion processes continue to be essential for the energy supply sector. A reliable energetic evaluation of these processes is crucial, particularly since the pollutants resulting from combustion have a significant impact on global warming. This work evaluates a combustion using the exergetic evaluation and the Physical Optimum (PhO) as it is described in VDI-Guideline 4663. Differences between PhO and exergy are investigated, allowing a distinct differentiation and examining the PhO's added value in combustion analysis. Based on the evaluation of a simulated methane combustion, this paper shows that the PhO-Factor may be used to evaluate combustion processes. However, it shows that the PhO of a combustion process is a simplification of this fuels exergy and does not provide advantages to the exergy evaluation. Nevertheless, an adaption of the PhO is not carried out in the context of this work since the minimal deviation of the simulated energy indicators currently cannot justify an adaptation. In addition, proposed adjustments of the reference value (PhO) could lead to the definition limits of the PhO-Factor being exceeded. The paper introduces the indirect PhO-Factor for a targeted process optimization. It is shown that in this case, the indirect PhO-Factor closely corresponds to the exergy efficiency.

Automated summary

This study evaluates a combustion process using the Physical Optimal (PhO) method and investigates the differences between PhO and exergy, showing that PhO may be used for combustion evaluation. However, it also demonstrates that PhO is a simplification of fuel exergy and does not provide advantages over exergy evaluation. No adaptation of PhO is made due to minimal deviation in simulated energy indicators, and proposed adjustments could exceed limits of the PhO-Factor. The introduction of the indirect PhO-Factor is proposed for targeted process optimization, which closely corresponds to exergy efficiency.