SymptomsWhen the HRSG temperatures are high (greater than 1,100 °F / 593 °C) as a result of supplemental firing, the default correlations in GateCycle can have difficulty matching HRSG vendor-predicted performance. CauseGateCycle (and most other commercial heat balance software packages) use the "Effectiveness - NTU" method to model HRSG heat exchangers. Most HRSG vendors use a much more detailed modeling method that requires tube-level geometric data rather than the overall surface areas required by GateCycle. The "Effectiveness - NTU" method does not account for radiative heat transfer that is present under heavy supplemental firing conditions. Furthermore, GateCycle assumes that the gas side limits the overall heat transfer coefficient. With heavy supplemental firing, this may not be the case as the steam side could be the limiting factor. We are aware of these issues and are working to add tube-level calculations to GateCycle. Unfortunately, the first release of this capability is targeted for internal GE use only. Some proprietary pieces must be removed and made more generic before we can release the feature commercially. ResolutionDownload the following document for instructions on tuning your GateCycle models to match HRSG vendor data. |
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