Modeling the influence of tube support plates on flow boiling and dryout of once-through steam generators

Abstract

Considering the tube support plates installed among the tube bundle of actual once-through steam generator, the mathematical model suitable for smooth channel was modified to numerically simulate the two-phase flow and heat transfer and dryout under three structures (no tube support plates, tube support plates with and without gaps). The results show that the slip ratio increases rapidly when fluid flows through the tube support plates, and then decreases rapidly under the strong disturbance caused by the turbulence transition at the downstream position of tube support plates. The maximum slip ratio for the case of TSPs with gaps is lower than that for the other two cases, which is conducive to prevent interphase slipping. The turbulence transition and great steam quality caused by heat transfer enhancement at the downstream position of tube support plates both have positive effects on tearing the annular liquid film, resulting in the dryout position being at the upstream position of that for the case of no tube support plates. The damage of dryout deterioration can be relieved significantly when considering tube support plates, and the corresponding rising amplitude of wall temperature at dryout position reduces from 300 K for the case of no tube support plates to 200 K. With the development of flow and heat transfer, the non-uniform levels of circumferential wall temperature for the cases of tube support plates with and without gaps show completely opposite trends.