Investigation On Gas-Liquid Two-Phase Flow Patterns And Flow Characteristics Across Tube Bundles

Gas-liquid two-phase cross flow is widely used in nature and chemical, power and other industry fields, which plays an important role in the practical application, especially the flow between the vertical upward pipes, such as two-phase flow in the water-cooled nuclear reactor systems and shell-and-tube heat exchanger. The study on flow pattern is always an important content of research field of two-phase flow. The characteristics of two-phase flow are critical to the design, operation and safety of the equipment.In this paper, flow pattern of gas-liquid two-phase flow across tube bundle is studied. High speed photography used to shoot the flow images, to achieve a visual, non-contact measurement, and will not interfere with the normal operation of equipment. Dynamic data acquisition instrument real-time acquires the pressure fluctuation signal, then analyze flow characteristics by the statistical analysis of the pressure fluctuation signal. This paper analyzes the flow characteristics of the system from the flow image and the pressure fluctuation signal.In the gas-liquid two-phase flow test rig, using a high-speed camera to obtain images of the vertical upward flow across three structures of tube bundles. Analyze flow characteristics of the image of typical flow pattern, establish the flow pattern map based on experimental data, and analyze the influence of bundle structure to range of flow pattern. Extract GLCM parameter of flow pattern continuous image, by analyzing the Lempel-Ziv measure of GLCM parameters and the information entropy of flow continuous image to study two-phase flow pattern evolution characteristics. Analyze the pressure fluctuation signal of different flow patterns in two groups test section, using recurrence plots and recurrence quantification to analyze the pressure fluctuation in the same pitch ratio bundles, using complexity measures and the attractor patterns to analyze the pressure fluctuation in the same arrangement bundles. Research found that high-speed photography method clear observed the change of flow pattern detail, in veins parameters of image, the complexity of ENT and COR have good coincide with information entropy of flow image, but the role of characterization of CON and ASM does not universal. The influence of pitch ratio to range of flow pattern is weaker than bundle arrangement. Study the differential pressure of same flow pattern found that the two-phase flow status of staggered bundle is sequential than bundle in-line. Study the differential pressure of different pitch ratio bundles found that the trends of two complexity measures and the attractor patterns under typical flow pattern were sensitive to the flow pattern transition, and have a well reflection to the dynamics structure of gas-liquid two-phase flow, can distinguish the flow pattern of two-phase flow. Therefore, the characteristics of flow pattern can be studied well by combining the high-speed photography method and nonlinear theory.