Transient Analysis of Temperature Distribution in Furnace Walls

The problem of transient temperature behavior of the steam generator evaporator tube walls caused by the feedwater system fallout is presented in this paper. The tubes are covered with brick material as to be protected from overheating in the first part of the furnace, while in the second part they are exposed directly to the hot gases. During normal operation the accumulated heat energy in the furnace wall may cause the tube wall temperature excursions in the shutdown period. The representative cutouts of the furnace walls in the three distinguished furnace positions are modeled by the code NISA with the purpose of obtaining transient temperature profiles across furnace walls. The steady-state conditions are tested and the results compared with the existing measurement data prior to the transient analysis. The tube wall temperatures really exceed maximum permissible temperature for the given tube material some 280 min after the feedwater system fallout has been shown by the transient analysis.