Study on Characteristics of Thermal-Hydraulics Phenomena in Steam Injector

Characteristics of thermal-hydraulic phenomena in the steam injector were examined. Two-types of a test section were used: a straight condensing section type and a taper condensing section type. In the straight condensing section type experiments, a water jet from a nozzle of 5 mm diameter flowed in to the test section concentrically. The inner diameter of the condensing section was 7, 10, or 20 mm and the length was 105 mm. Steam flowed into the peripheral space between the water jet and the inner wall of the condensing section. Experiments of the taper condensing section type were similar to those of the straight condensing section type. The inner diameter of the condensing section at the outlet of the water nozzle was 13.25 mm and the condensing section length was 52.9 mm. The inner diameter of the throat was 4 mm and the throat length was 5 mm. The vapor condensation rate, i.e. the condensation heat transfer rate, did not depend on the subcooling of the water jet. It was proved that the overall condensation heat transfer is controlled by the radial heat transport in the water jet since the condensation heat transfer resistance is much smaller than that of the radial heat transport in the water jet. The radial heat transport only depends on the jet flow rate. The criterion of the jet disruption was correlated by the Kelvin-Helmholtz instability wave length. The prediction provided conservative results; approximately one-tenth. When the condensing section was tapered such as the steam injector, the water jet became more stable. It was suggested that the accelerated water jet becomes more stable. (authors)