ライブラリ登録: Guest

ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Evaluation of a Method for Predicting Heat Transfer During Boiling of Mixtures in Plain Tubes

Get access (open in a dialog) DOI: 10.1615/IHTC15.fbl.008351
pages 2615-2629

要約

Due to environmental concerns and resulting regulations, new refrigerants with low GWP and low ODP have been and are being formulated to replace present refrigerants. Most of them are mixtures of two or more fluids. Heat transfer coefficients of mixtures are lower than of pure fluids due to sensible heat transfer and mass transfer effects. Correlations for pure fluids therefore cannot be directly applied to mixtures. Some methods for predicting heat transfer of mixtures have been proposed but none of them has been verified with more than a few data sets. The predictive method tested during the present research consists of using the Thome-Shakir correction factor for pool boiling in the nucleate boiling region and the Bell-Ghaly correction factor in the region in which nucleate boiling has been completely suppressed. While the Bell-Ghaly correction factor was developed for condensation, its use here is justified as the mechanism of heat and mass transfer during evaporation without bubble nucleation is the same as during condensation. While the Thome-Shakir correction factor has been tried before, this combination of Thome-Shakir and Bell Ghaly correction factors does not seem to have been used before. For comparison, calculations were also done using the Thome-Shakir factor alone. These correction factors were used together with five well-verified correlations for pure fluids. These are: Shah (1982), Gungor & Winterton (1987), Chen (1966), Gungor & Winterton (1987), and Liu & Winterton (1991). These were compared to a data base consisting of 700 data points for 42 binary and ternary mixtures of 18 fluids from 18 studies. The fluids included halocarbons, hydrocarbons, and carbon dioxide. The range of parameters covered by the data is: tube diameters 1.9 to 14 mm, horizontal and vertical orientations, flow rates from 50 to 740 kg/m2s, reduced pressures from 0.05 to 0.63, temperature glides upto 28 C, and boiling numbers from 0.4 x 10-4 to 31.1 x 10-4. The correlations of Shah, Gungor & Winterton (1987), and Liu & Winterton correlated all data with mean absolute deviations of 20.3, 21.2, and 20.3 percent respectively. The deviations with the other two correlations were much higher. While further data analysis is desirable, good agreement with such a wide range of data suggests that this combination of Thome-Shakir and Bell-Ghaly correction factors may be generally applicable.