Air Conditioning and
Refrigeration Systems Oil Fouling
Oil fouling of the heat transfer surfaces of
air conditioning and refrigeration systems, will cause a loss
of about 7% efficiency the first year, 5% the second year,
and 2% per year the following years. This loss will continue
to accumulate until equilibrium is reached between flow force
and adhesion. At this point the oil boundary layer formed
has achieved its maximum thickness, producing maximum loss
of efficiency. Usually, the efficiency degradation will peak
somewhere between 20% and 30 %. Published ASHRAE information
confirms these observations. According to ASHRAE, performance
is degraded by as much as 30% due to the build-up of lubricants
on internal surfaces.* Higher percentages up to 40% have been
observed in systems 20 years old or older.
* "A Survey of Refrigerant Heat Transfer
and Pressure Drop Emphasizing Oil Effects and In-Tube Augmentation;"
ASHRAE Winter Symposium of 1987; Schlager, Pate, and Bergles.
