Dynamic Viscosity under Pressure for Mixtures of Pentaerythritol Ester Lubricants with 32 Viscosity Grade:  Measurements and Modeling

Abstract

The dynamic viscosity under pressure of three mixtures of pentaerythritol ester lubricants (PEs) has been measured using a rolling-ball viscometer for several temperatures with an experimental uncertainty of 3%. The first one is a multicomponent mixture of several PEs named in the present work as PEC5-C9 lubricant; the second one is a binary mixture of pentaerythritol tetra(2-ethylhexanoate), PEB8, and pentaerythritol tetraheptanoate, PEC7, with a PEB8 mole fraction of 0.6670; and the third one is another binary mixture of PEB8 and pentaerythritol tetrapentanoate, PEC5, with a PEB8 mole fraction of 0.6911. The two binary mixtures, xPEB8 + (1x)PEC7 and xPEB8 + (1x)PEC5, have been prepared with the same viscosity grade as the PEC5-C9 lubricant (VG32). A total of 1176 experimental measurements of the rolling time have been performed at pressures up to 60 MPa for the determination of 196 dynamic viscosity data points. The viscosities of these binary mixtures have been compared with the predicted values obtained by using several viscosity models (Grunberg-Nissan and Katti-Chaudhri mixing laws, self-referencing model, hard-sphere theory, and free-volume model). All methods predict dynamic viscosity values for the two binary mixtures that agree with the experimental data within an average mean deviation of 10% over the entire temperature and pressure ranges. The best predictions were found with the free-volume model, for which the average mean deviation for both mixtures is lower than 4%. Parameter values for the self-referencing model were determined from experimental viscosity data of several pure PEs. These parameters permit the estimation of viscosity values of PE lubricant of unknown composition, when a viscosity value at any temperature and pressure is available. This model predicts the viscosities of PEC5-C9 lubricant with an average deviation of 4%.

High‐pressure viscosity and density of carbon dioxide + pentaerythritol ester mixtures: Measurements and modeling

“…The values calculated with the free-volume model agree with the experimental data within AADs ranging from 6 to 37%, whereas the MD ranges from 17 to 44%. These results contrast with those obtained for mixtures of POE lubricants, 24 for which the free volume model can predict the viscosity values with an AAD lower than 4.4%. If the ' mix , a mix , and B mix values are fitted against the experimental viscosities of the mixtures, these deviations are much lower (AAD \ 3%) but then, the model is not predictive.…”

“…66 for mixtures of methane and decane as well as of methane and toluene. These results contrast with those obtained for mixtures of POE lubricants, 24 for which the Katti and Chaudhri and Grunberg and Nissan mixing laws predict the viscosity values with an AAD lower than 5.4%. Hence, it can be concluded that these simple mixing laws are not valid for viscosity predictions of size-asymmetrical mixtures.…”

“…For pure POEs, the parameters values were published in previous work. 24 The values of the parameters for pure carbon dioxide were fitted using our experimental viscosity values 17 and minimizing the AAD between the experimental and calculated data. We report in Table 5 the values of the parameters and the deviation results obtained for this compound.…”

“…At present, our research group is studying the density [19][20][21] and viscosity [22][23][24] in broad ranges of temperature and pressure of pentaerythritol esters considered as precursors of POE oils (i.e., as components of refrigerant commercial oils), the solubility 25 of carbon dioxide in pentaerythritol esters, and the density and viscosity 17 of mixtures containing POE lubricants and CO 2 .…”

Study of the effects of pressure on the viscosity and density of diisodecyl phthalate

“…The viscosity measurements at high pressure were performed in a rolling-ball viscometer [15][16][17][18] (Ruska 1602-830) from 303.15 K to 373.15 K and at pressures from 0.1 MPa to 60 MPa. Several elements of the apparatus were modified from the original device [17].…”