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Início Arquivos Thermal Letter Representantes Futuras reuniões Assembléia das Conferências Internacionais de Transferência de Calor
International Heat Transfer Conference 13

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

A COMPARISON WITH THE THREE-ZONE MODEL FOR FLOW BOILING HEAT TRANSFER IN SMALL DIAMETER TUBES

D. Shiferaw
School of Engineering and Design, Brunel University, Uxbridge, West London, United Kingdom

Tassos G. Karayiannis
Department of Mechanical and Aerospace Engineering Brunel University London, Uxbridge, UP8 3PH, UK

D. B. R. Kenning
School of Engineering and Design, Brunel University, Uxbridge, West London, United Kingdom ; Department of Engineering Science Oxford University, Oxford, OX1 3PJ, UK

DOI: 10.1615/IHTC13.p28.160
13 pages

Resumo

Flow boiling heat transfer experimental results, obtained in two stainless steel tubes of internal diameter 4.26 mm and 2.01 mm using R134a as the working fluid, indicate that the local heat transfer coefficient increases with heat flux and is independent of vapour quality when this is less than about 40% to 50% for the 4.26 mm tube and 20% to 30% for the 2.01 mm tube, conventionally interpreted as nucleate boiling. Above these quality values, the separate graphs merge into a single line for heat transfer coefficient decreasing with increasing vapour quality. The data in the apparently-nucleate boiling condition are compared with a recent state-of-the-art three-zone evaporation model for the confined bubble flow regime without a nucleate boiling contribution. The model predicts the experimental data reasonably well but does not predict correctly the trends for changing pressure and diameter. Some suggestions are made for improving the model. The comparisons made in this paper support the statements by the developers of the model and others that the application of conventional macro flow boiling correlations to micro tube flow boiling heat transfer may not necessarily have a sound physical basis.

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Measurement of fluid temperature with an arrangement of three thermocouples