Effect of low heat and mass fluxes on the boiling heat transfer coefficient of R-245fa
File(s)
Published version
Author(s)
Van den Bergh, WJ
Moran, HR
Dirker, J
Markides, CN
Meyer, JP
Type
Journal Article
Abstract
In-tube flow boiling at low mass and heat fluxes is of increasing interest particularly for low-concentration solar power systems, refrigerators, heat pumps, and other thermal management components and systems. In this study, the flow boiling of R-245fa was investigated experimentally for vapour qualities ranging from 0.05 to 0.90, mass fluxes of 40, 60 and 80 kg/m2s, and heat fluxes of 2.5, 5.0 and 7.5 kW/m2. Tests were done at quasi-steady-state conditions in a horizontal smooth tube with an inner diameter of 8.31 mm and a heated length of 0.8 m, at a saturation temperature of 35°C. It was found that the heat transfer coefficient was influenced by both the mass and heat fluxes. At any given vapour quality and heat flux combination, an increase in the mass flux resulted in an increase in the heat transfer coefficient. However, the magnitude of the increase and sensitivity to the mass flux was not the same in all of the test cases. Higher vapour quality cases were more sensitive to the mass flux than lower vapour quality cases, except at low heat flux conditions. In the most peculiar case, at the lowest considered heat flux of 2.5 kW/m2, severe sensitivity to mass flux was observed at vapour qualities between 0.2 and 0.3. For all other heat fluxes, the heat transfer coefficient was found to be independent of the vapour quality except when the mass flux was high, where increased vapour quality resulted in improved heat transfer coefficients. Various correlations were investigated, but none of them captured the trends for the lowest heat flux.
Date Issued
2021-12
Date Acceptance
2021-07-12
Citation
International Journal of Heat and Mass Transfer, 2021, 180, pp.1-19
ISSN
0017-9310
Publisher
Elsevier BV
Start Page
1
End Page
19
Journal / Book Title
International Journal of Heat and Mass Transfer
Volume
180
Copyright Statement
© 2021 The Author(s). Published by Elsevier Ltd.
This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
License URL
Sponsor
The Royal Society
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://www.sciencedirect.com/science/article/pii/S0017931021008498?via%3Dihub
Grant Number
AQ150077
EP/T03338X/1
EP/P004709/1
Subjects
Mechanical Engineering & Transports
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
Publication Status
Published
Article Number
121743
Date Publish Online
2021-07-31