Analytical Study of Unsteady Boiling Characteristics of Steam Generator

Abstract

Currently, research on the efficiency of the film heater, which is a surface heating element, is being actively conducted as it is a potential alternative to the sheath heater. However, research on the heat transfer phenomenon and the performance of the film heater is insufficient. In this study, the performance of the sheath heater and the film heater were compared and analyzed, and the heat transfer pattern according to the arrangement of the heating wire was analyzed. To inspect the heat transfer performance, the external heat transfer and internal flow characteristics of the steam generator were determined, and a study on the performance of the steam generator according to each design variable was conducted. The Eulerian multiphase model was used to conduct the multiphase flow analysis, and the wall boiling model was used to conduct the phase change analysis. Among the models analyzed in this study, the model in which the heating wire was arranged along the flow path and the length of the induction was extended by 50% showed the best performance. Compared to the base model, the steam generation time was improved by 33.3% and the steam ejection time was improved by 17%. These times were improved because the heating wire arrangement of the film heater was optimized along the fluid channel. The U-shaped heating wire arrangement enabled a stable steam injection, and in the case of the normal film heater and fluid channel following heater, a large portion of the heating wire was located around the center. Consequently, steam was formed at the center of the housing. We believe that the results of this study can be applied to various fields in consideration of the advantages of the film heater package, free pattern design of printing, and economy.