Prediction of wall temperature and oxide scale thickness of ferritic-martensitic steel superheater tubes

Based on the thermal deviation theory and local energy and mass balance of the superheater tube, a new method of calculating tube wall temperature is proposed. The wall temperature distribution and the thickness of oxide scale of the superheater tubes of a supercritical boiler are estimated over the length of the steam flow path for different periods of service. This calculation of oxide scales on the steam side takes into account ash deposits on the flue gas side. The results of oxide scale thickness of boiler superheater tubes for different exposure time are compared with field measurement data. There is a sudden increase in the wall temperature at the tube elbow (position N) because of high gas temperature and high heat transfer coefficient. The distribution of the gas temperature field along the height of the heating surface has a great influence on the final wall temperature calculation results.