Power law exponents for single bubbles growth in nucleate pool boiling at zero gravity

Abstract

Nucleate pool boiling is an important boiling mode used in various fields of application. Bubble detachment and new bubble generation at the nucleation site is an important aspect of the process under terrestrial conditions. This sequence prevents prolonged observation of bubble growth phenomena. The problem can be circumvented by performing single bubble growth experiments under zero gravity conditions. Many experiments of this type are performed in a specially designed cell on board the International Space Station. Several combinations of boiling experimental parameters (pressure, heat flux, waiting time, degrees of subcooling) are tested. The bubble size evolution curve was found to represent the influences off the individual parameters best. Fitting attempts show that the experimental bubble growth curves can be nicely described by power law correlations. An analytical solution is given for the evolution of the liquid temperature field within the experimental test cell, in the absence of boiling incidents. It is shown that the time evolving difference between the solid/liquid interfacial temperature and the liquid saturation temperature is the basic factor that determines the bubble growth exponent. As an outcome, the whole experimental information on the bubble growth curves of 160 different boiling conditions is compressed in the form of tables that include the corresponding power law factors. These tables not only allow the reconstruction of the examined boiling curves but can also generate boiling curves in a dense grid of boiling conditions through interpolation of existing boiling data. The latter offers coherence and continuity in boiling computer codes over a broad range of conditions.