The employment of a vertical sparger in Direct Contact Condensation (DCC) is a common design practice in industrial applications. This configuration might result in unstable condensation conditions, generally defined as chugging, characterized by bubble implosions and pressure spikes affecting the condensation efficiency. Starting from the high quality video recorded during an experimental investigation, an image processing technique is implemented. It consists of a recognition procedure and three different reconstruction models which attempt to individuate the bubble boundary in every video frame and to reproduce the 3D shape of the bubble in order to assess its surface area and volume. These outputs allow to obtain all the experimental parameters describing the chugging phenomenon. An analytical model is then developed. The model follows the approach of Sargis et al. and Ali et al. which is based on the main conservation laws. The validation is performed against their results: the wave shapes agree well confirming the capability of the model to simulate the phenomena. The model is then applied to the small scale experiment. Finally, the comparison between the analytical predictions and the experimental results is carried out. Except for the interface velocity, a close agreement is found, pointing out the efifciency of the image processing. The interfacial condensation heat transfer coefficient is also evaluated: it ranges between 104and 105W/(m2K), in conformity with the values reported in the literature.

Experimental image process and analytical model of direct contact condensation in chugging regime

STARNELLA, GIUSEPPE;Inzoli, Fabio;Mereu, Riccardo
2016

Abstract

The employment of a vertical sparger in Direct Contact Condensation (DCC) is a common design practice in industrial applications. This configuration might result in unstable condensation conditions, generally defined as chugging, characterized by bubble implosions and pressure spikes affecting the condensation efficiency. Starting from the high quality video recorded during an experimental investigation, an image processing technique is implemented. It consists of a recognition procedure and three different reconstruction models which attempt to individuate the bubble boundary in every video frame and to reproduce the 3D shape of the bubble in order to assess its surface area and volume. These outputs allow to obtain all the experimental parameters describing the chugging phenomenon. An analytical model is then developed. The model follows the approach of Sargis et al. and Ali et al. which is based on the main conservation laws. The validation is performed against their results: the wave shapes agree well confirming the capability of the model to simulate the phenomena. The model is then applied to the small scale experiment. Finally, the comparison between the analytical predictions and the experimental results is carried out. Except for the interface velocity, a close agreement is found, pointing out the efifciency of the image processing. The interfacial condensation heat transfer coefficient is also evaluated: it ranges between 104and 105W/(m2K), in conformity with the values reported in the literature.
17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017
Analytical model; Bubble; Chugging; Direct contact condensation; Image processing; Nuclear Energy and Engineering; Instrumentation
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/1064774
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