Measurement and Correlation of Densities and Dynamic Viscosities of Perfluoropolyether Oils

The densities and dynamic viscosities of five different polydisperse perfluoropolyethers (PFPE) were measured at atmospheric pressure over the combined temperature range 263.15–373.15 K. For one PFPE being considered as a high-temperature high-pressure viscosity standard reference material, measurements were made on two separate samples to examine the lot-to-lot variability in density and viscosity; significant variability was observed only for the viscosity data. Experimental data were correlated as a function of temperature. A simple quadratic equation was used for density, while three equations (DIPPR, VFT, and Waterman) were applied to the viscosity data. The DIPPR equation represented the viscosity data with deviations approximately an order of magnitude lower than the other two equations

Density, Speed of Sound, and Viscosity Measurements of Reference Materials for Biofuels

Measurements of density, speed of sound, and viscosity have been carried out on liquid certified reference materials for biofuels as a function of temperature at ambient pressure. The samples included anhydrous and hydrated bioethanol and two biodiesel fuels from different feedstocks, soy and animal fat. The ethanol samples were measured from a maximum temperature of 60 to 5 °C (speed of sound) and to −10 °C (density and viscosity), respectively. The biodiesel samples were characterized from 100 °C (density and viscosity) and from 70 °C (speed of sound) to 10 °C (animal fat-based) and 5 °C (soy-based). Densities were measured with two vibrating-tube instruments of different accuracy. The speeds of sound were measured with a propagation-time method in an acoustic cell that was combined with one of the densimeters. Viscosities were measured with an open gravitational capillary viscometer and with a rotating concentric cylinder viscometer, according to Stabinger. The measurement results are reported with detailed uncertainty analyses

Chemical and Thermophysical Characterization of an Algae-Based Hydrotreated Renewable Diesel Fuel

Second-generation renewable fuels are synthesized through biochemical and thermochemical processes from nonfood biomass feedstock. The resultant fuels are similar to aliphatic synthetic fuels produced through the Fischer–Tropsch process, which contain mainly linear and lightly branched alkanes. We applied the advanced distillation curve method to an algae-based hydrotreated renewable naval distillate fuel (HRD-76) to measure its boiling temperature as a function of distillate volume fraction. Analysis of the bulk fuel sample through nuclear magnetic resonance spectroscopy, gas chromatography, and mass spectrometry showed the principal components to be linear and branched alkanes containing 14–18 carbon atoms. The speed of sound and density of the fuel were estimated from its composition and compared with experimental data measured with a density and sound speed analyzer. The estimates were within 5% of the experimental values. The boiling temperature, density, and composition data were used to estimate the calculated cetane index of the fuel. We also measured the cloud point of the fuel through a constant cooling rate method with optical detection of paraffin wax precipitation. The measured cloud point was consistent with reported values for hydrotreated renewable fuels, which tend to be higher than cloud points of diesel fuels derived from petroleum. The quantitative thermophysical and chemical data can be used to improve combustion modeling of HRD-76 and other second-generation renewable fuels

Thermodynamic Properties of 1,1,1,2,2,4,5,5,5-Nonafluoro-4-(trifluoromethyl)-3-pentanone: Vapor Pressure, (<i>p</i>, ρ, <i>T</i>) Behavior, and Speed of Sound Measurements, and an Equation of State

We report comprehensive thermodynamic property measurements of 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone. The (<i>p, ρ, T</i>) behavior was measured from <i>T</i> = (225 to 470) K with pressures up to 36 MPa with a two-sinker densimeter. These measurements include compressed-liquid states and states in the extended critical region. The vapor-phase speed of sound was measured from <i>T</i> = (325 to 500) K with pressures up to 1.7 MPa with a spherical acoustic resonator. The vapor pressure was measured in the spherical resonator from <i>T</i> = (325 to 440) K with a static technique. The density and speed of sound of the liquid was measured from <i>T</i> = (278 to 308) K at atmospheric pressure (<i>p</i> = 83 kPa) in a benchtop instrument employing a vibrating-U-tube densimeter and a time-of-flight speed-of-sound technique. These data, together with selected data from the fluid manufacturer, have been used to develop an equation of state explicit in the Helmholtz energy covering the fluid region. The equation of state represents the present experimental vapor-pressure data with an RMS deviation of 0.066 %, the (<i>p, ρ, T</i>) data to 0.067 %, and the speed-of-sound data to 0.029 %. This fluid is of interest as the working fluid in Rankine-cycle power applications and as a fire extinguishing agent; it is also known by the trade names Novec-649 and Novec-1230