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High Temperature Oxidation
- Thread starter Eissa1406
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As I recall it follows a larson-miller type correlation, easy to calculate by hand. For ferritic alloys, I recall the estimate inlcuded the oxide scale had a coefficient of thermal conductivity equal to 10% of the parent alloy.
In large coal fired boilers ( USA- no steam to reheat bypass system) , the section most affected by oxide scale is the final reheater banks. When tube sections are removed for analysis, it is found that the oxide scale is in layers, as in tree rings. Each ring could be exactly correlated to a hot MFT main fuel trip, or a turbine trip at full load. Under that scenario, it takes 3 seconds for a the coal mills and coal/air conduits to clear out, and another 10 seconds for the hot gases to pass over the rheater tubes, so the tubes heat up to as high as 1200 F during that transient .
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick
In large coal fired boilers ( USA- no steam to reheat bypass system) , the section most affected by oxide scale is the final reheater banks. When tube sections are removed for analysis, it is found that the oxide scale is in layers, as in tree rings. Each ring could be exactly correlated to a hot MFT main fuel trip, or a turbine trip at full load. Under that scenario, it takes 3 seconds for a the coal mills and coal/air conduits to clear out, and another 10 seconds for the hot gases to pass over the rheater tubes, so the tubes heat up to as high as 1200 F during that transient .
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick
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