|M.Sc Thesis||Department of Mechanical Engineering|
|Supervisor:||Prof. Emeritus Hetsroni Gad|
Horizontal annular two-phase flow in pipes occurs in a wide range of industrial applications such as chemical plants, oil wells and pipelines, fluidized bed combustors, evaporators and so on. The understanding of the hydrodynamics and the heat transfer mechanism is essential to improve the design of the various applications. The aim of the study is to measure the heat transfer coefficient and to determine its dependence upon film thickness and flow pattern.
In the present research, the flow patterns at different air and water flow-rates were investigated in a 25 mm internal diameter horizontal pipe. The water superficial velocity was set in the range from 24.2 m/s to 41.5 m/s, while the air superficial velocity varied from 0.02 m/s to 0.09 m/s. The flow patterns were visualized using a high speed video camera, and the film thickness was measured by the conductive tomography technique. The heat transfer coefficient was calculated from the temperature measured using the infrared thermography method.
It was found that the heat transfer coefficient at the bottom of the pipe is up to three times higher than that at the top, and becomes more uniform around the pipe for higher air flow-rates. Correlations on local and average Nusselt number were obtained and compared to results reported in the literature. The behavior of local heat transfer coefficient was analyzed and the role of film thickness and flow pattern was clarified.