EBSILON®Professional Online Documentation
The examples given in VDI 2048, Sheets 1,2,3 have been calculated by means of the procedure described here using the option “Manual input of equations“. The results have been compared to those in VDI 2048 and data specified on the additional data carriers, respectively. A more detailed comparison for the scenario “with corrections / with correlations“ from the retrofit example from Sheet 2 can be found in the further course of this chapter, as well as in Appendix 6.2 for the guarantee certification of a combined-cycle power plant from Sheet 3.
For the example from Sheet 2, the results published in VDI 2048 and Ebsilon matched to a large extent. This applies to the raw data analysis, the corrected values, their confidence interval and related corrections as well as to the correlations and the guarantee comparison.
Minor differences in the corrected values (e.g. in the case of the measurement mHK) amount to less than a per mill of the estimated value and are thus significantly smaller than the confidence interval. They are due to the fact that the additional iteration according to Chapter "Theoretical basis", equation 18 used in Ebsilon contains additional terms. As shown in “Significance of the additional x-x0 terms for the convergence of the additional iterations“, due to these terms the iteration may lead to a solution with a slightly smaller error sum of squares. This is also the case in the retrofit example. Differences of this order of magnitude have no significance for practical purposes. They become noticeable particularly in such places where the system has physical degrees of freedom. E.g. this is the case for the distribution of the estimated and not directly measured mass flows mAnz6 and mAnz5.
Concerning the example from Sheet 3 (preparing an acceptance, combined cycle) the VDI data and Ebsilon also match to a large extent. Remaining deviations are due to differences in the applied material values for gases, in Ebsilon the calculation according to FDBR is used. In the raw data analysis, this becomes noticeable particularly in the heat balances of the boiler and gas turbine. The table uncertainties, however, are treated as relative uncertainties according to VDI, as described in the corresponding “Help”-Chapter.
The comparison can be found at the following links: