Tube Within The Flow Of Dry Pilot Study

Considering the relationship between the phenomena of critical heat flux (CHF) and the safety of nuclear reactor, the research of CHF on experiment and theory has been carried in detail. By now, many achievements have been acquired, including hundreds of empirical correlations to predict the CHF value, and models for CHF in different conditions, what's more, more basic research about two-phase flow, heat transfer, and behavior of gas bubble etc. Whereas, all approach of predicting CHF value or explaining the phenomena, has disadvantages of limited parameter range and accuracy. Therefore, sequential research on CHF is necessary.When in accidental conditions of nuclear reactor, the mass flux of coolant is very low. In such condition, the steam quality is high, and the mechanism of CHF is mainly controlled by bulk flow, whereas microcosmic parameters near the CHF area are affected by the flow conditions in whole tube which called "upstream memory effect". In this case, we need more knowledge of such CHF phenomena, and this article mainly carries out research on such phenomena.In low mass flux and high outlet quality conditions, experiments have been performed using vertical heated tube, cooled by water, to determine CHF value for a uniformly heated section. The inner diameter of the heated section is 0.014m and heated length is 2.1m, and 93 data have been achieved in this experiment. Coolant pressure, velocity of coolant, inlet quality and outlet quality are in the range 0.142-1.472MPa, 0.086-0.777m/s, -0.374-0.432 and 0.410-1.000 respectively. The discussion on the effect of many parameters on CHF value is provided in the later section.What's more, based on existing knowledge on mechanism of such CHF phenomena and mass and heat transfer in such conditions, this article provides a numerical calculation method to predict the CHF value in such condition. And by compared with our experimental data, this method is valid. In addition, this articlemodifies the Hewitt&Kearsey correlation, extending the pressure range of the correlation.In the last section of this article, many correlations, including Biasi correlation, Sudo correlation, CISE correlation, and 1995 Look-up Table, are compared with our experimental data. Based on these results, evaluations on these correlations are provided, and because of lack of considering on up-stream memory effect, the correlations which mainly predict CHF value based on local parameters, have considerable error.