ISSN Online: 2377-424X
International Heat Transfer Conference 3
VAPOR VOID FRACTION IN SUBCOOLED BOILING AND IN SATURATED BOILING SYSTEMS
Abstrakt
The results of an analysis for predicting the
vapor void fraction in boiling systems are presented.
For two phase systems in thermodynamic equilibrium
it was shown (1, 20) that three effects,
i.e., of flow profile, vapor concentration profile
across the duct and of relative velocity must be
taken into account. It is shown here that when the
bulk liquid is either subcooled or superheated a
fourth effect, that of the non-uniform liquid temperature
distribution, must be considered. These
four effects are included in an analytical expression
for predicting the void fraction in saturated
or subcooled boiling. A method for also taking
into account the nucleating characteristics of the
heated surface is given since this effect also influences
the non-equilibrium void prediction.
Satisfactory agreement is shown between the analytical
results and experimental data.