Experimental Investigation of Two-Phase Flow Instability in HTR-10 Steam Generator

Abstract

For ultra-high temperature operation of the 10 MW High-Temperature Gas-cooled test Reactor (HTR-10), the operation parameter of its steam generator will deviate from the original design. Two-phase flow instability may occur. To investigate this phenomenon, experiments were carried out using two full-scale helical tubes. A segmented electrical heating approach was employed for these two tubes. The stability boundary was searched by adjusting inlet resistance coefficient or heating power. This study examined the stability of the HTR-10 OTSG at low power levels and explored the influences of operational parameters. Out-of-phase pulsation type density wave oscillation was observed during the stability experiments. The stability of HTR-10 OTSG was verified at 10% power level under non-uniform heating (close to convection heating). The systems with high inlet resistance coefficients became stable as increasing power level. Consequently, HTR-10 OTSG can operate stably during ultra-high temperature operation conditions. For the influence of heating power distribution, the stability under uniform heating was more conservative compared to non-uniform heating. The influences of inlet resistance coefficient, heating power, system pressure and inlet temperature on the stability were investigated under uniform heating. HTR-10 OTSG became stable when increasing inlet resistance coefficient or decreasing heating power. Within system pressure range of 1.5 MPa to 3.5 MPa, increasing system pressure made the systems more stable. Flow instability may occur easier with an increase in inlet temperature in the range of 50℃ to 210℃.