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ISSN Online: 2377-424X

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

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

Correlation of Transition Boundaries to and from Annular Flow Regime of Ammonia Evaporating Inside a Horizontal Internally Spirally Grooved Tube

Get access (open in a dialog) DOI: 10.1615/IHTC15.tpf.009876
pages 8457-8470

要約

The flow pattern and heat transfer of evaporating ammonia inside a horizontal spirally grooved tube were experimentally investigated. The test tube was made of STB-340-SC steel and the maximum inner diameter, the groove height, the number of grooves and the lead angle, are 12.5 mm, 0.4 mm, 32 and 15 degrees, respectively. Experimental conditions are 30 to 100 kg/(m2s) in mass velocity, about 0.7 MPa in pressure, and 0 to 20 kW/m2 in heat flux.
The flow regimes of the obtained experimental results were classified by using the authors' previously proposed method, which is based on the analysis of the trends of heat transfer coefficients and the average wall temperatures at the upper and lower halves. The present experimental data were sorted into the following three kinds of flow regimes: separated flow with liquid meniscus, annular-mist flow, and dispersed mist flow. The measured flow regime transition qualities were compared with some available correlations for both a smooth tube and a grooved tube. The two correlation equations were proposed to predict the transition qualities between separated and annular flow regimes, and between annular and mist flow regimes. The former one was developed by using the Mori et al.'s correlation equation for wetted perimeters of flow boiling inside a smooth tube. And the latter was developed based on the Yoshida et al's correlation for the dryout qualities of fluorocarbon refrigerants evaporating inside a internally spirally grooved tube.