New Insitu Technique for Measuring the Concentration of Lubricant on a Boiling Heat Transfer Surface.
New Insitu Technique for Measuring the Concentration of
Lubricant on a Boiling Heat Transfer Surface.
Kedzierski, M. A.; Bruno, T. J.; O'Neill, M. B.
NISTIR 6110; 43 p. January 1998.
Sponsor:Department of Energy, Washington, DC
Available from: National Technical Information Service
Order number: PB98-124837
lubricants; refrigerants; absorption; alternative
refrigerants; boiling; enhanced; fluorescence; heat
transfer; refrigerant/lubricant mixtures; reflected
harmonic; alternative refrigerants
This paper presents a technique for using the
fluorescent properties and/or the harmonic focusing
properties of several commercial lubricants to measure
the concentration of lubricant on an aluminum vignetting
target. The measurement method is being developed to
determine the concentration of lubricant insitu on a
boiling heat transfer surface. The heat transfer
performance of a boiling surface is a strong function of
both the type of lubricant and its concentration in the
refrigerant. In general, severe boiling performance
degradations may occur for higher concentrations of
lubricant on the surface. The lubricant is
preferentially drawn out of the bulk
refrigerant/lubricant mixture by the boiling process and
accumulates on the surface in excess of the bulk
concentration. However, different lubricants accumulate
on the heat transfer surface by different amounts for
the same bulk concentration. The excess lubricant
resides in a very thin layer on the surface.
Accordingly, the ability to measure the lubricant
concentration on the heat transfer surface would lead to
a fundamental understanding of the mechanism by which
lubricants can degrade or improve boiling performance.
The lubricant concentration on a vignetting target was
found to be linear with respect to the fluorescence
intensity and the reflected harmonic from the surface.
Consequently, the results of this study have shown that
it is feasible to use the fluorescence and reflected
harmonic measured from a boiling heat transfer surface
to obtain the concentration of lubricant on the surface.