The flow patterns and heat transfer are tested experimentally and numerically in a bubbly flow downstream of a sudden pipe expansion. Using shadow photography, measurements of the bubble size were carried out. Using a PIV system, fluid phase velocities were measured. The Eulerian method was employed by the numerical model. The set of RANS equations was used for the simulation of bubbly twophase flows. Using the Reynolds stress model, the turbulence of the carrier liquid phase was expected. A substantial increase (up to 30 percent) is achieved in wall friction in the bubbly flow downstream of the suddenly expanding pipe. In bubbly flow, the average and fluctuating flow structures with small values of β ≤ 10 percent are close to that of a one-phase fluid flow. In the shear layer, the peak of axial and radial variations of the carrier fluid (liquid) velocity are observed in the bubbly flow. A large improvement in the heat transfer rate (up to 300 percent) resulted from the addition of air bubbles. After the point of flow re-attachment, the main increase in heat transfer is observed. After the point of flow re-attachment, the main increase in heat transfer is observed. In general, the distributions of the Nusselt number in the bubbly flow have a qualitatively similar character to that of turbulent separated flows for single-phase fluid.
Author(s) Details
Laboratory of Problems of Heat and Mass Transfer, Kutateladze Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, 630090, Novosibirsk, Acad. Lavrent'ev Avenue, 1, Russia.Rudolf Rüffer ESRF-The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France.
Maksim Pakhomov
Laboratory of Thermal and Gas Dynamics, Kutateladze Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, 630090, Novosibirsk, Acad. Lavrent'ev Avenue 1, Russia.
Viktor Terekhov
Laboratory of Thermal and Gas Dynamics, Kutateladze Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, 630090, Novosibirsk, Acad. Lavrent'ev Avenue 1, Russia.
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