Viscosity Measurements of Ammonia, R32, and R134a. Vapor Buoyancy and Radial Acceleration in Capillary Viscometers
Arno R. Laesecke, T Luddecke, R F. Hafer, Dylan Morris
The saturated liquid viscosity of ammonia (NH3) and of the gydrofluorocarbons difluoromethane (Ch2F2, R32) and 1,1,1,2-tetrafluoroethane (CF3-CH2F, R134a) was measured in a sealed gravitational viscometer with a straight vertical capillary. The combined temperature range was from 250 to 350 K. The estimated uncertainty of the ammonia measurements is plus or minus 3.3% and plus or minus (2-2.4)% for the gydrofluorcarbons. The results are compared with literature data which have been measured with capillary viscometers of different design. Agreement within the combined experimental uncertainty is achieved when some of the literature data sets are corrected for the vapor buoyancy effect and when a revised radial acceleration correction is applied to data which were obtained in viscometers with coiled capillaries. An improved correction for the radial acceleration is proposed. The need to extend international viscometry standards to sealed gravitational capillary instruments is obvious because the apparent inconsistencies between refrigerant viscosity data from different laboratories cannot be explained by contaminated samples.
, Luddecke, T.
, Hafer, R.
and Morris, D.
Viscosity Measurements of Ammonia, R32, and R134a. Vapor Buoyancy and Radial Acceleration in Capillary Viscometers, International Journal of Thermophysics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=831617
(Accessed December 10, 2023)