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Arnautovic, Zlatan ; Welzl, Matthias ; Heberle, Florian ; Brüggemann, Dieter:
Enhanced heat transfer correlation for nucleate boiling of fluid mixtures.
In: International Journal of Heat and Mass Transfer.
Bd. 231
(2024)
.
- 125804.
ISSN 0017-9310
DOI: https://doi.org/10.1016/j.ijheatmasstransfer.2024.125804
Abstract
To replace state-of-the-art working fluids in thermodynamic cycles in respect to environmental and efficiency perspective is a current engineering task. In this context, fluid mixtures represent an important research approach. However, the existing correlations for heat transfer coefficient for mixture boiling are complex and uncertain due to diverse thermophysical properties.
In this study, nucleate boiling heat transfer coefficients were experimentally determined for the binary mixtures ethanol/water and ethanol/MM on a vertical falling film at a copper tube for 1 bar and a heat flux range of 40 to 100 kW/m². The heat transfer measurements for ethanol/water show a well-known behavior, and coefficients decrease below the pure fluid heat transfer coefficients due to mass transfer resistances. In contrast, measurement data for the ethanol/MM mixture has shown an increase in heat transfer coefficients compared to the pure fluids. The Marangoni effect may have caused this increase. An enhanced heat transfer correlation was proposed based on the correlation of Schlünder under consideration of surface tension and density differences of the pure components. This newly developed correlation is able to predict the heat transfer characteristics of ethanol/water and ethanol/MM very well, and the deviation in the calculation is reduced significantly. The average mean deviation for ethanol/water was 13.3 % and for ethanol/MM only 11.1 %. The general validity of the developed correlation was determined based on ten additional binary mixtures from literature in a pressure range of 1–6 bar and in a heat flux range of 30–1000 kW/m². The overall mean deviation concerning the entire data set for the binary mixtures was 18.5 % for Fujita and Tsutsui, 20 % for Inoue and Monde, 18.6 % for the Thome and Shakir correlation, 16.1 % for Schlünder, and 11.6 % for the enhanced correlation.