Effect of Refrigerant Oil Additive on R134a and R123 Boiling Heat Transfer Performance.
Effect of Refrigerant Oil Additive on R134a and R123
Boiling Heat Transfer Performance.
Kedzierski, M. A.
International Journal of Refrigeration, Vol. 30, No. 1,
144-154, January 2007.
refrigerants; additives; heat transfer; boiling;
two-phase mixture; polyolester; R134a; R123;
This paper investigates the effect that an additive had
on the boiling performance of an R134a/polyolester
lubricant (POE) mixture and an R123/naphthenic mineral
oil mixture on a roughened, horizontal flat surface.
Both pool boiling heat transfer data and lubricant
excess surface density data are given for the R134a/POE
(98% mass fraction/2% mass fraction) mixture before and
after use of the additive. A spectrofluorometer was used
to measure the lubricant excess density that was
established by the boiling of the R134a/POE lubricant
mixture before and after use of the additive. The
measurements obtained from the spectrofluorometer
suggest that the additive increases the total mass of
lubricant on the boiling surface. The heat transfer data
show that the additive caused an average and a maximum
enhancement of the R134a/POE heat flux between 5 kW m-2
and 22 kW m-2 of approximately 73% and 95%,
respectively. Conversely, for nearly the same heat flux
range, the additive caused essentially no change in the
pool boiling heat flux of an R123/mineral oil mixture.
The lubricant excess surface density and interfacial
surface tension measurements of this study were used to
form the basis of a hypothesis for predicting when
additives will enhance or degrade refrigerant/lubricant