Research On Effect Of Rolling Condition On Gas-water Flow In Horizontal Tubes

Experimental and theoretical studies were carried out to investigate the characteristics of flow pattern, void fraction and frictional pressure drop of gas-water flow in horizontal transparent tubes under rolling state, the inner diameter of which was 25mm and 34.5mm respectively.The experiments were performed on a rolling test-bed whose rolling period and rolling angle could be adjusted discretionarily. On the basis of experimental research on the two-phase flow, and making reference to the flow pattern under steady state, the flow pattern of gas-water flow was proposed in horizontal tubes under rolling state. It was found that the flow pattern under rolling state was different from that in stationary horizontal tubes. And experimental results showed that there were two flow patterns appeared alternately in rolling tubes under some circumstances.A method was proposed to determine the flow pattern in horizontal tubes according to the pressure drop characteristics under rolling state. According to analyses of the effect of tube diameter, rolling period and rolling angle on flow pattern, the flow pattern map of gas-water flow in rolling tubes was drew, which could provide some reference in engineering.Unstable flow pattern, the additive force and the change of gravitation force on the two-phase flow were the primary effect factors of void fraction under rolling state. In different flow pattern, void fraction was variational with the change of quality velocity of flow and the situation of pipe. On the basis of experiments, formulas were proposed for calculating the void fraction of bubble flow and annular flow. Through the comparisons between the calculating formula and experimental results, it was found that the formulas could reflect the change of void fraction in horizontal tube under rolling state very well. Through the force analyses of single phase water with rolling motion and experimental researches on the effects of tube diameter, rolling angle, rolling period and Reynolds number on single-phase frictional coefficient, a formula was proposed to calculate the single-phase frictional coefficient. It was testified that the formula calculating results were in a good accordance with the experimental results which showed the curve of single-phase frictional coefficient vs. time length was presented in a sinusoid mode. Furthermore, the formulas of calculating the fractional pressure drop of bubble flow and annular flow in rolling tubes were proposed according to homogeneous model and separate model respectively. The results showed that the calculating values of the formulas matched the experimental result well.The investigative results of the thesis could provide reference for creating the math-physics model and calculating the characteristics of two-phase flow and heat transfer of two-phase flow in rolling tubes.