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Proceedings of CHT-17 ICHMT International Symposium on Advances in Computational Heat Transfer
May 28 - June 1, 2017, Napoli, Italy

DOI: 10.1615/ICHMT.2017.CHT-7


ISBN Print: 9781-56700-4618

ISSN: 2578-5486

CFD multiphase modelling for the nanofluid boiling of the salt solution in a symmetric rectangular boiler

pages 955-972
DOI: 10.1615/ICHMT.2017.CHT-7.1040
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SINOPSIS

Nanofluid boiling is analysed numerically in a horizontal rectangular symmetric tube as a part of study to improve heat transfer in vapour absorption refrigeration systems (VARS). Computational fluid dynamics (CFD) simulations are performed to assess the effect of varying nanoparticle concentrations, fluid velocity and boiler temperature on the boiling and phase change characteristics of the system. Previous research concentrates on water based fluids or commonly found refrigerants and heat transfer fluids. The nanofluid used in this study is acetone/zinc bromide (ZnBr2) based on zinc oxide (ZnO) nanoparticles. The process was modelled using ANSYS® Fluent V.15 using the volume of fluid (VOF) multiphase flow model. An extra user defined code was applied from the literature for boiling of nanofluids to model the mass transfer on boiling. It was found that the increase in nanoparticles loading (0, 0.1, 0.3, 0.5 & 1 vol. %) leads to an increment in the exiting vapour volume fraction and the heat transfer coefficient. This is primarily due to an increase in the heat transfer in the system due to the increased thermal conductivity in the nanofluid. Incremental increases in the boiler temperature (330, 333, 335 K) creates an increase in the vapour volume fraction and corresponding decrease in the heat transfer coefficient because of increasing the vapour adjacent the wall, which has low heat transfer coefficient. The phases that treated in this case were liquid acetone, vapour acetone, liquid Acetone / ZnBr2 and solid nanoparticles cloud. In addition, this study evaluates the key characteristics of the nanofluid system, and how the different component and phases behave when a single component evaporates.

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