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Simulation of condensation in a subcooled bubbly steam-water flow along a large vertical pipe

Lucas D., Prasser H.

Archives of Thermodynamics

2005

Vol. 26, no. 4

49-59

Detailed experimental data obtained at the TOPFLOW facility for steam-water vertical pipe flow were used to test the complex interaction of local bubble distributions, bubble size distributions and local heat and mass transfer. Steam is injected into subcooled water and condenses during the upward flow. The model considers a large number of bubble classes (50). This allows the investigation of the influence of the bubble size distribution. The results of the simulations show a good agreement with experimental data. The condensation process is clearly slower, if large bubbles are injected (4 mm holes). Also the bubble break-up has a strong influence on the condensation process because of the change of the interfacial area. Some unsureness arises from the unknown interfacial area for large bubbles and possible uncertainties of the heat transfer coefficient.

Evolution of flow patterns, gas fraction profiles and bubble size distributions in gas-liquid flows in vertical tubes

Lucas D., Krepper E., Prasser H. M.

Transactions of the Institute of Fluid-Flow Machinery

2003

nr 112

37-46

Air-water flow at ambient conditions in a vertical pipe an inner diameter of 51.2 mm is investigated. An electrode wire-mesh sensor enables the measurement of the phase distribution with a very high resolution in space and in time. Local bubble size distributions are calculated from the data. The measurements were done in distances from the gas injection device. As a result, the development of bubble size distributions as well as the development of the radial gas fraction profiles can be studiet. It was found, that the bubble size distribution as well as local effects determine the transistion from bubble flow. The data are used for the development of a model, which predicts the development of the bubble size distribution and the transition from bubble flow in the case of stationary flow in a vertical pipe.