Visualization of Nucleate Flow Boiling for an R22/R114 Mixture and Its Components.
Visualization of Nucleate Flow Boiling for an R22/R114
Mixture and Its Components.
Kedzierski, M. A.; Didion, D. A.
Experimental Heat Transfer, Vol. 3, 447-463, 1990.
nucleation; convective flow; quartz tube; refrigerants;
mass flow; test apparatus; mass quality; thermal
Visualization of bubble nucleation during
forced-convective flow inside a horizontal, electrically
heated quartz tube was done in order to establish a
comparison of this phenomenon between refrigerant
mixtures and their pure components. The specific
phenomena investigated were the suppression of
nucleation due to increased mass flow quality while
holding all other conditions fixed, and the comparison
of the nucleate activity of the binary mixture to the
nucleate activity of the pure components. The fluids
investigated were a 37.7 mol% R22/62.3 mol% R114 binary
mixture and the individual components R22 and R114.
These fluids were pumped through an abraded,
electrically heated quartz tube. A 16-mm high-speed
camera was used, at 7000 frames/s, to film the boiling
process. Detailed measurements of bubble frequency and
bubble size were possible at low pressures, allowing
direct calculation of the latent heat load required to
nucleate a single bubble. Further work is required to
develop a method that ensures statistically sound bubble
frequency measurements. However, the standard
deviations of the bubble diameter measurements were
acceptable. The films were used to visually demonstrate
the suppression of nucleation with increase in quality
for R114, R22, and an R22/R114 mixture. The films
suggest that, for a given quality, R114 exhibits much
more nucleation than either R22 or the mixture, while
the amount of nucleation demonstrated by R22 and the
mixture was comparable even though the mixture was
mostly R114 by mole. Arguments using the latent heat of
vaporization, the vapor density, and the liquid thermal
conductivity have been made to explain the visual