Annular two phase flow is encountered in many industries which use steam generators in power plants and boilers. Especially, disturbance wave flow which large water lumps move with faster velocity on the thin water film in annular flow region is an important flow regime, since dryout of water film always occurs at the thin base film between two successive disturbance waves in the case that the interval of the disturbance waves become large accidentally. Therefore, it is important to clarify the behavior of disturbance waves and base film. However, mont of the studies with respect to the behavior limited to the adiabatic flow, that is, air/water system, and even in the boiling flow limited to the behavior of only disturbance waves (frequency, velocity, and spacing). Therefore in this paper we focused on not only the behavior of the disturbance wave but also the base film in the boiling upward annular two phase flow. The results are summarized as follows : (1) Liquid film thickness in steam-water system fluctuates at random compared with air-water system, This is because the flow in steam-water system is always developing toward downstream side due to the heating. In particular, liquid film thickness in steam-water system does change largely with low frequency in the case the flow is accelerated rapidly due to the high heat flux. These large liquid lumps seem to be the traces of the liquid slug in the froth flow region. (2) Liquid film thickness fluctuation in steam-water system is influenced by the heating length clearly. However, statistical film thickness characteristics, i.e., minimum, average, and maximum film thickness, are almost the same even in the different heating length. (3) The dryout always occurs at the thin liquid film between large liquid lumps which are the traces of liquid slug in froth flow region.
|ジャーナル||Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B|
|出版ステータス||出版済み - 11 2006|
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