Dynamic Entropy Investigation of Feed Water Heater in Nuclear Power Plant During Start-Up Process

Abstract A dynamic simulation model has been established to study the entropy characteristics of the feed water heater start-up process, and the dynamic entropy analysis was conducted. The effects of step and continuous changes in extraction steam flow on the entropy characteristics of the start-up process were investigated. With the increase of the extraction mass flow rate, the entropy generation rate at steady state increased gradually. To study the effects of the continuous change in extraction steam flow, the entropy was characterized and analyzed with three types changes: the quick opening (QO), the linear and the equal percentage (EP). The optimal start-up method should have the EP extraction steam flow change characteristics with the smallest accumulated entropy generation (28.16 MJ/K), which was 32.01% less than that of the linear flow characteristic and 47.548% less than that of the QO flow characteristic. The proportion of entropy generation rate of each control volume under the design condition was obtained, and the proportion of steam condensing zone was the largest (46.08%). This study could provide important guiding significance for the start-up process of the feed water heater.