A Proposed Pressure–Viscosity Coefficient Model Through Processing of Falling Body Viscometry Data for Di-(Ethylhexyl) Sebacate

Abstract

The relative volume and falling body viscosity of a common high-pressure rheology reference lubricant, di-(2-ethylhexyl) sebacate (DEHS), are presented. Relative volume measurements up to 300 MPa are completed with a piezo-bellows relative volume cartridge. Viscosity measurements up to 1 GPa are completed with a pressurized falling body viscometer. Digital signal-processing routines used for viscosity and relative volume measurements are discussed. The viscosity data are then fit into the modified Yasutomi model. Integration of this fit, as well as that of other models found in the literature, is used to propose a pressure–viscosity coefficient model. Comparisons are first made to DEHS, followed by the application of the study results to 17 other well-documented fluids. The validity of this method is investigated using the integrated viscosity model of DEHS as well as other available datasets presented in literature. The authors perform a comparison between the calculated pressure–viscosity coefficient α* and those presented for the mentioned datasets created with the signal-processing routines. The analysis shows that the proposed pressure–viscosity coefficient model is able to accurately capture the inverse of the asymptotic isoviscous pressure response of the majority of data when compared to other calculation methods.