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Previously published experimental viscosity data at low density, originally obtained using all-quartz oscillating-disk viscometers for R134a and six vapors of aromatic hydrocarbons in the temperature range between 297 K and 631 K at most, were re-evaluated after an improved re-calibration. The relative combined expanded (   $$k=2$$  k = 2 ) uncertainty of the re-evaluated data are 0.2 % near room temperature and increases to 0.3 % at higher temperatures. The re-evaluated data for R134a as well as for the vapors of mesitylene, durene, diphenyl, fluorobenzene, chlorobenzene, and  p -dichlorobenzene were arranged in approximately isothermal groups and converted into quasi-isothermal viscosity data using a first-order Taylor series in temperature. Then, the data for R134a were evaluated by means of a series expansion truncated at first order to obtain the zero density and initial density viscosity coefficients,    $$\eta ^{(0)}$$  η ( 0 ) and    $$\eta ^{(1)}$$  η ( 1 ) . For the six aromatic vapors, the Rainwater–Friend theory for the initial density dependence of the viscosity was used to derive    $$\eta ^{(0)}$$  η ( 0 ) values. Finally, reliable    $$\eta ^{(0)}$$  η ( 0 ) and also    $$\eta ^{(1)}$$  η ( 1 ) values for R134a were selected as reference values in the measured temperature range to be applied when generating a new viscosity formulation.

international journal of thermophysics

Recommended Values of the Viscosity in the Limit of Zero Density for R134a and Six Vapors of Aromatic Hydrocarbons as Well as of the Initial Density Dependence of Viscosity for R134a. Revisited from Experiment Between 297 K and 631 K