ISSN Online: 2377-424X
ISBN Print: 0-85295-345-3
International Heat Transfer Conference 10
MECHANISTIC MODEL FOR NUCLEATE BOILING CRISIS AT DIFFERENT GRAVITY FIELDS
Résumé
According to the mechanistic model discussed the
nucleate boiling crisis is connected with sharp expansion
of dry patches area at the heated wall. It occurs when the
surface - averaged heat flux becomes equal to maximum
heat flux per one dry patch. The latter is defined by liquid
influx to the liquid meniscus boundary which in its turn
depends on the liquid properties and mean thickness of
liquid macrofilm which exists under vapor blanket before
boiling crisis. The mean dry patch size is supposed to be
proportional to vapor bubble departure diameter. The
proposed model is applicable both to pool and flow boiling
and satisfactorily describes experimental results by Gambill
et al who investigated boiling crisis at swirl flow in tubes.
In this case the effective centrifugal acceleration is used in
the correlation for pool boiling CHF instead of standard
gravitational one. For high subcooling conditions the flow
boiling CHF correlation based on Reynolds analogy was
developed. In the case of swirl flow of subcooled liquid the
critical heat flux value is chosen as a maximum one of two
predictive magnitudes.