Investigation Of Direct Contact Condensation Of Saturated Steam On Free Subcooled Liquid

When the nuclear reactor is in the state of leaking, the boric water's gravity characteristics can be used to supply water to core passively, which can cool the core urgently. While at the beginning of this process, because the steam condenses rapidly on the sub-cooled liquid, which makes the pressure of CMT alter violently, the flow of supplying water diminishes and so affects the safety of nuclear reactor. According to the two different state of having sparger and not having sparger, the author of this paper has had experimental research and numerical simulation to the characteristics of saturated steam condensing on free sub-cooled liquid with direct contact, therefore, got many results such as the responding characteristic to pressure in the system, temperature distribution of 2D and the interfacial heat transfer coefficient of condensation. Visualized research showed that: at the beginning of the research, the injection of steam crushed into the liquid layer rapidly and in the interaction district of converse-taper, most of the steam mixed with the deep sub-cooled liquid and disappeared, only a little steam rose to the vapor space of CMT in the form of small bubble. With the processing of experiment, the speed of steam injection slowed down, which crushed the surface of the liquid into a converse-tapered hole. Only a little steam condensed, the rest steam gathered into a big air mass and flowed into the steam space of CMT, the pressure of CMT balanced gradually. In the end of the experiment, with the rising temperature of the whole liquid layer, the interaction district of converse-taper disappeared gradually, the steam condensed weakly on the nearly horizontal surface of the liquid, and the pressure of the system remained unchangeable. According to the different phenomenon of condensation, the condensation process can be divided into "balanced pressure" and "steady pressure" these two phases. In the "balanced pressure" phase, the heat transfer coefficient ranged from 3150W/m2·K to 9410W/m2·K when sparger is added, while the heat transfer coefficient ranged from 180W/m2·K to 2138W/m2·K without sparger; so the heat transfer coefficient decreased 76%--85% when sparger is added, the effect of slowing down condensation is obvious. In the "steady pressure" phase, the heat transfer coefficient was lower, it ranged from 50wto 100w, sparger hadn't any influence on it. In the "balanced pressure" phase, the heat transfer coefficient rose as the rising of the initial pressure, decreased as the rising of the initial temperature. In the "steady pressure" phase, initial pressure and initialtemperature haven't any obvious influence on the heat transfer coefficient. A correlation was concluded by the experiment, it is about the average heat transfer coefficient under different condensation state: having sparger and without sparger. This correlation is applicable in the range: initial pressure of PRZ 200~600KPa, initial temperature of CMT 10~80℃.Without sparger: balanced pressure steady pressureSparger balanced pressure Sparger 1# Sparger 2# steady pressure Responding characteristic to pressure of CMT was mainly affected by the initial pressure of PRZ and the initial temperature of CMT: under the same initial temperature, the higher the pressure was, the longer the time of pressure balancing, and the higher the balanced pressure would be; under the same initial pressure, the higher the temperature was, the shorter the time of pressure balancing. Adding sparger shortened the time of pressure balancing, compared with no sparger, the time of pressure balancing shortened 20%-70%; the higher the initial pressure of PRZ, the lower the initial temperature of CMT, the bigger the shortened extent would be. Without sparger, because of the mixture of the steam, the temperature of each radial point of the liquid vibrated, temperature distribution was not even; the higher the initial pressure...