Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

CRITICAL HEAT FLUX IN SUBCOOLED FLOW BOILING

Get access (open in a dialog) DOI: 10.1615/IHTC11.2750
pages 261-277

Abstrakt

The present paper reports a survey of recent experimental works performed to get parametric trends of the critical heat flux (CHF) in water subcooled flow boiling, with special concern with high liquid velocity and subcooling, small diameter channels, and low-intermediate pressure, together with a review of current modelling analysis of it. Under the above thermal hydraulic and geometric conditions the CHF is proved to be very high (up to many tens of MW/m2) such as to match the request of fusion reactor high heat flux components requirement for their thermal hydraulic design. From the experimental viewpoint experiments carried out so far show the parametric trends of the CHF in terms of subcooling, mass flux, pressure, channel diameter and length, channel orientation, tube wall material and thickness, and peripheral nonuniform heating. Passive techniques for the CHF enhancement, such as twisted tapes, helical1y coiled wires, and hypervapotron are also reviewed. Apart from the specific difficulty of properly modelling the CHF phenomenon for a large range of conditions, a major drawback of many of existing theories is the use of empirical constants to adjust the model with the data, making them complex correlations which spoil the original idea of the model. Among the many existing models, the superheated layer vapour replenishment and the liquid sublayer dryout theories proved to be capable of predicting the CHF under these conditions, also extending its good performance to uniform and non uniform heating of the channel and swirl flow as well.