Entropy generation analysis for fine flow states in PWR fuel assembly

Although the development of pressurized water reactor (PWR) technology has been relatively well developed so far, the depth of research on the thermo-hydraulic characteristics of the in-reactor coolant, especially the energy dissipation characteristics, still needs to be explored further. As an energy conversion system for PWR, entropy generation analysis plays a vital role in obtaining the irreversible loss of the coolant quantitatively and directionally, which is scarce. It is difficult to access the full coolant energy losses and thermal–hydraulic properties, and to provide direction and schemes for optimizing the flow field in the core. In this paper, the energy dissipation of the flow field is finely analyzed in the 5x5 rod bundle of the PWR core. For the irreversible dissipation of the flow energy of the coolant, the pulsation dissipation entropy generation and wall friction entropy generation account for about 90% and 10%, respectively, and the direct dissipation entropy generation is negligible. For the high dissipation region, the distribution of pulsation dissipation entropy generation in space has a directional role. The irreversibly dissipated energy is calculated using the definition of entropy generation, and the dissipation characteristics of cross-flow kinetic energy in different regions are analyzed accordingly. Lastly, the irreversible dissipation of temperature difference heat transfer is considered and correlated with the above hydraulic viscous dissipation, and the negative correlation characteristics of the two are found. Meanwhile, the parameter constructed by the two together has some advantage in flow field evaluation.