期刊
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
卷 140, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijmultiphaseflow.2021.103649
关键词
Liquid film thickness; Condensation; Heat transfer; Waves analysis; Chromatic confocal sensor
类别
资金
- European Space Agency through the MAP Condensation program ENCOM [AO-2004-096]
- Department of Industrial Engineering of the University of Padova [BIRD 187743]
This study investigated the liquid film thickness and heat transfer coefficients during annular flow condensation in a small diameter channel, using specialized measurement techniques and algorithms to analyze the wave structures of the liquid film. The experimental results contribute to a better understanding of the heat transfer mechanisms involved in phase change processes.
The determination of the liquid film thickness during annular flow condensation in a small diameter channel is complex and very rare in the literature, although important to understand the heat transfer mechanisms involved during the phase change process. In the present paper, the liquid film thickness and heat transfer coefficients have been measured during vertical downflow condensation inside a 3.38 mm inner diameter channel. Condensation tests have been run with R245fa at 40 degrees C saturation temperature and mass velocity ranging from 30 kg m(-2) s(-1) to 150 kg m(-2) s(-1). The test section is composed of two heat transfer sectors connected with a glass tube. The glass tube has been realized with a special external shape that produces a magnification of the liquid film thickness and allows the use of a chromatic confocal sensor. The liquid film thickness is determined by coupling a shadowgraph technique with the measurements performed by the chromatic confocal sensor. An ad-hoc algorithm has been developed for the statistical characterization of the wave structures in terms of amplitude, frequency and velocity, with the aim to better understand how the interfacial waviness affects the heat transfer. (C) 2021 Elsevier Ltd. All rights reserved.
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