Simulation of the supercritical boiler evaporator operation under conditions of a rapid power increase

This study describes a distributed-parameter mathematical model developed to simulate the operation of a supercritical power boiler evaporator in the transient regime. This model is based on balance equations that describe the mass, momentum, and energy conservation principles of a single-phase flow. In the two-phase flow region, relations representing a homogeneous flow were used. To compute the waterwall tube temperature histories, two-dimensional transient heat conduction equations were solved for the analysed cross-sections. Because the fluid velocity varies along the length of the evaporator tubes (transition from the liquid to the gaseous phase), a methodology for performing thermal and flow computations was proposed, making it possible to achieve solution stability. This methodology is the primary scientific novelty of the present study. The results obtained using the developed method were verified using measurement data. These data were related to the operation of a supercritical power boiler at a Polish power plant. The measurements were performed in the areas of steam superheaters and economizers, for which corresponding mathematical models have previously been developed. The satisfactory agreement between the selected measured and computed histories confirmed the accuracy of the proposed models, including the boiler evaporator model. These models can support the boiler design process.