The progress of the two-phase flow research is divided by four stages. these periods are 1948-1959, 1960-1970, 1971-1979, and 1980-1988. In this 3rd report, the development of research on annular flow and annular-mist flow in the second period has been described. The progress of analysis of the liquid film thickness has been discussed and the initial stage of research on wave phenomena and entrainment has been introduced.
There are many basic studies of dropwise condensation on a small condensing surfaces, but there are few practical studies on large condensing surface. The relation between the behavior of departing drops and the heat transfer on a horizontal tube was inverstigated in the previous paper. In this paper, we theoretically study the heat transfer on a vertical row of horizontal tubes. We find that both the sweeping and the covering actions by the passing condensate yield the maximum heat transfer at second tube from the top of the tube arrangement.
In this paper, the relationship between the flow behavior and the pressure fluctuation was investigated because it was confirmed from the 1st and 2nd Report that the flow behavior was related to the pressure fluctuation. In results, the flow became unstable in the transition region between the flow with a deposit bed and the one with a moving bed, and it was found that the pressure fluctuation became very large. Furthermore, it was confirmed that the relationship between the velocity fluctuations of fluid and solid particles, and the flow behavior were the same as the one between the pressure fluctuation and the flow behavior. Therefore, it could be considered that the velocity fluctuations are related to the pressure fluctuation, and the simulation model of the pressure fluctuation containing the factor of velocity fluctuations of fluid and solid particles was proposed. The calculated values of the pressure fluctuations using this model were in good agreement with the experimental results.
A twin fiber otpic liquid film sensor system has been developed, which is able to measure the local thickness and the interfacial wave velocity of liquid film in gas-liquid annular two-phase flows simultaneously. This sensor system consists of two independent mono-fiber optic sensors. Each mono-fiber optic sensor can distinguish only the crest and the trough of the interfacial wave and can measure the film thickness at these parts. A propagation velocity of the interfacial wave has been measured by a time-of-flight method. Both simulation experiments and applications of this sensor system to an actual air-water annular two-phase flow in a vertical tube have shown that the simultaneous measurements of the local thickness and the interfacial wave velocity of the liquid film can be done accurately.