Electrical properties and kinematic viscosity of biodiesel

Abstract

Kinematic viscosity and electrical properties (permittivity and electrical conductivity) of biodiesel samples were determined in the temperature range between 298 K and 343 K. The samples were produced from sunflower, olive, canola, corn, soybean, grapeseed and jatropha vegetable oils. Electrical measurements were carried out in the frequency range from 20 Hz to 2 MHz. From the analysis of the experimental results, two models were developed to estimate the kinematic viscosity from electrical properties. The first model estimates the kinematic viscosity from relative permittivity measurements, with an RMS uncertainty below 0.4 mm2/s for all the samples. The second model allows the estimation of the kinematic viscosity from conductivity measurements, with an RMS uncertainty below 0.07 mm2/s for all the samples. The models and procedures presented in this work reduce the measuring time for kinematic viscosity from several minutes to a few seconds. The results are relevant for biodiesel characterization, on-line viscosity monitoring systems, and in measurements where time is prioritized over accuracy. Moreover, a power law scaling was found relating kinematic viscosity and electrical conductivity. This result is relevant for the study of processes that depend on these transport properties, such as flow electrification. For the samples studied, the fitted value of the power law exponent is -0.67±0.02.