Experimental Investigation of an Application of Two-Phase Flow Differential Pressure Measurement in Vertical Square Channel

The experimental work described in this paper deals with an experimental research of two-phase flow focused on the study of thermal hydraulics of steam generating facilities for NPPs, like BWR reactors and steam generators. The results of this research can be used for development of new methods for the control and measurement of the operating parameters of these facilities at normal and abnormal operational conditions. Moreover the results are also applicable for a development of a method for a determination of two-phase flow regimes by pressure fluctuation analysis. The main idea of those methods is based on the measurement of pressure and pressure difference in steam-water mixture and their further analysis by mathematical methods of signal processing. Based on the results of these analysis, represented by statistical and frequency parameters of pressure signal, it is possible to determine other parameters of two-phase flow such as void fraction, slip ratio and flow regime of two-phase flow. This method may be applied to the steam generator, where it can be used for a measurement of a generated steam flow rate by the measurement of a differential pressure between two points located at the outer shell of the steam generator at steam-water mixture level. This method has several advantages, over other methods and might improve the total efficiency of the power plant. In this paper the validation method at low pressure is presented. For this experimental work an experimental facility was made consisting of 1.5 m tall square channel with the dimensions of 200 × 200 mm. This channel was equipped with electrical heaters with power of 9 kW in the bottom part and they serve for production of steam-water mixture. This facility was used for a measurement of an absolute pressure and a pressure difference of two-phase flow for various conditions — power and geometries of grid elements. A set of pressure data for every measurement was analyzed by basic statistical methods and results of those analyzes for various conditions were compared. This comparison was focused on the determination of dependencies among a parameters of analyzed pressure signal from a heater power and geometry of a grid which have significant influence on void fraction. The results of this comparison are presented and discussed in this paper as well as the method used for the statistical analysis. Further possibilities and limitation of this method are described, mainly the performance of the measurement instrumentation that has a significant influence on the final result. In the conclusion the applicability of this method for real power facilities and next direction of this research are discussed.