Effect of Refrigerant Oil Additive on R134a and R123 Boiling Heat Transfer Performance and Related Issues for GSA.
Effect of Refrigerant Oil Additive on R134a and R123
Boiling Heat Transfer Performance and Related Issues for
Kedzierski, M. A.
NISTIR 7132; 63 p. June 2004.
refrigerants; additives; heat transfer; alternative
refrigerants; boiling; enhanced heat transfer;
fluorescence; non-adiabatic lubricant excess surface;
refrigerants/lubricant mixtures; polyolester lubricant;
naphthenic mineral oil
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 mixture of
R134a and a POE for before and after the addition of the
additive. A spectrofluorometer was used to measure the
lubricant excess density that was established by the
boiling of an R134a/POE lubricant (98% by mass/2% by
mass) mixture on a flat boiling test surface. The
measurements obtained from the spectrofluorometer
suggest that the additive increases the total mass of
lubricant on the boiling surface. The heat transfer data
shows that the additive caused an average and a maximum
enhancement of the R134a/POE heat flux between 5 kW/m2
and 22 kW/m2 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. In
addition, a maximum degradation of the heat flux for the
R123/mineral oil mixture was observed to be
approximately 27% at a heat flux of 73 kW/m2. The
lubricant excess surface density and interfacial surface
tension measurements were used to hypothesize a physical
explanation for the enhancement/degradation mechanism
associated with large liquid-vapor surface-tension
additives. The results of a compatibility study of the
additive with common refrigerants and lubricants are
included along with a survey of chiller manufactures on
the use of additives.