Silvia Daniela Romano

Numerical expressions for viscosity, surface tension and density of biodiesel: analysis and experimental validation

The purpose of this work was to test the accuracy and predictive power of different numerical methods in order to compute reliable values of viscosity, surface tension and density of biodiesel in a wide range of temperature. Available formulae in literature were used to compute the mentioned properties in the temperature ranges in which they were developed. To validate the numerical expressions we have used experimental measurements of viscosity, surface tension and density performed in our laboratory and published in the literature. In this article, the results obtained by the application of different expressions are shown and possible sources of discrepancy between measured and predicted values are mentioned. The method that predicts the best results is identified for each property. In order to achieve a better fitting to the experimental data, corrections in the expression of the temperature-dependent properties were made when they were necessary.

Induced electric birefringence and viscosity studies in microemulsions

Abstract The Kerr constant was determined for the AOT-water-dodecane water-in-oil microemulsion. The goal of these experiments has been to test the validity of the theoretical approach of van der Linden, S. Geiger and D. Bedaux, Phys. A., 156 (1989) 130, which explains the electro-optical process through an elastic deformation of the droplets. The bending modulus of the curved surfactant monolayer along different paths of the phase diagram was measured. It was concluded that for concentrations relatively far from phase transition regions the theory can account for the experimental results. However, we have measured the Kerr constant, relaxation times and viscosity in microemulsion-based (gelatin) gels. These magnitudes have been measured as a function of gelatin concentration. For low biopolymer concentrations, Kerr constants do not vary too much, whereas in a certain concentration range (about 3–4%), they increase abruptly. This behaviour is similar to those of electric conductivity and viscosity. We have estimated the characteristic size of anisotropic microstructures. The possibility of the presence of a branched structure has been analysed by using a stretched-exponents approach proposed by M. Daoud and J. Klafter, J. Phys. A: Math. Nucl. Gen., 23 (1990) L981.

Application of Dielectric Spectroscopy to the Characterization of FAME in Biodiesel Production

During the production process of biodiesel, the mixture of fatty acid methyl esters (FAME) obtained from the transesterification process must be separated from glycerin and then purified in several steps. This chapter discusses the application of the measurement of electrical properties to obtain quantitative indication of the advance of the purification process and the conversion to biodiesel. The results presented in this chapter show that permittivity and conductivity measurements, as a function of temperature, provide relevant information on the efficiency of the successive washing steps of FAME. Moreover, the presence of contaminants in FAME and biodiesel may be detected by measurements of the characteristic electrical parameters. This is particularly important for the characterization of the final product.

Introduction to Biodiesel Production

Biodiesel [1, 2, 3, 4, 5] is a liquid biofuel obtained by chemical processes from vegetable oils or animal fats and an alcohol that can be used in diesel engines, alone or blended with diesel oil.

Rheological Measurements in Titania Gels Synthesized from Reverse Micelles

Abstract TiO2 sol and gel systems have been synthesized by hydrolysis of titanium butoxide in microemulsions W/O. Different systems compositions were prepared at constant W o = [H2O]/[AOT] and changing R = [H2O]/[Ti(BuO)4]. Experimental measurements show a progressive increase of the viscosity with time, characteristic of a sol-gel transition. The rheology of the transition was studied by following the behavior of viscoelastic parameters (G′, G″ and η*) as a function of time at different frequencies. The possibility to apply standard percolation theory was discussed. The application of two alternative growth models-either “fractal growth model” or “nearly linear growth model”-has been analysed.

Viscosity of Three Biodiesel Fuels: Experimental Data vs. Prediction Models

In this paper we study the predictive capacity of three methods to compute biodiesel viscosity and their behavior in different ranges of temperature (those able to be measured in laboratory and those of interest in the study of atomization and combustion) and we compare the results with the viscosity data obtained in our laboratory for three biodiesel from different feedstock. We also compare our experimental viscosity values with literature data in the same range of temperature to analyze differences in the tendency of evolution of this property with temperature.

Rheological and optical properties in systems containing TiO2 nanoparticles

Abstract In order to follow the sol–gel transition in systems containing TiO2 nanoparticles rheological and optical measurements were performed. Samples were prepared adding titanium(IV) butoxide (hydrolysis and condensation processes) to water/AOT/isooctane microemulsions. We prepared different systems at constant Wo=[H2O]/[AOT] while varying R=[H2O]/[Ti(BuO)4] to study the behaviour of viscoelastic parameters (G′, G′′ and η*) as a function of time at different frequencies as well as to analyse the Kerr constant (B) as a function of R. This work discusses the application of different theoretical approaches: scaling theory, ‘fractal growth model’ and ‘nearly linear growth model’. These experiments were complemented with light scattering measurements. Either static and dynamic optical determinations show an abrupt increase in the size of scattering particles. A significant increase in B values was observed for concentrations below gelification point when they were compared with those determined by light scattering.

Introduction to Dielectric Spectroscopy

This chapter presents the theoretical elements necessary to understand dielectric spectroscopy measurements. Low-frequency measurements are introduced in terms of lumped circuit parameters and other concepts of circuit theory. High-frequency measurements are discussed within the transmission line formalism. Propagation in coaxial lines is presented in terms of incident and reflected waves, characteristic impedances and reflection coefficients. Relevant aspects of experimental techniques are explained, including requirements for temperature control, sample cells design, laboratory procedures and electronic instruments for low- and high-frequency measurements.

Dielectric Techniques for the Characterization of Raw Materials and Effluents in Biodiesel Production

This chapter discusses the application of dielectric measurements to pure and used vegetable oils of different origins. The electrical properties of the effluents at the different stages of the purification process of biodiesel are also presented. The results of dielectric measurements of treated vegetable oils, compared with pure oils, are useful to determine the efficiency of the different treatment procedures, since they give a clear indication of the presence of water and contaminants. In addition, values of the refractive index of pure vegetable oils at different temperatures are given. The comparison of the electrical properties of the effluents with those of the clear water, are used to provide a quantitative indication of the degree of advance of the washing process, and also to verify its completion.

Standards for Fuel Characterization

There is no doubt about the importance of quality control of biodiesel to provide users with a reliable and consistent fuel quality which guarantees a good engine performance. For this reason, the fuel is characterized by measuring different properties according to international standards. This chapter presents the most important characterization properties, form the standpoint of the biodiesel producer. Since standards require the measurement of several properties and most of the necessary measuring equipment is expensive, and in many cases operated by highly trained personnel, the complete characterization and quality control of the biofuel is usually carried out only in industries with large-scale production capacity. Most small and medium producers are not always able do so. However, some equipment can be designed and built at a reasonable cost, following the specifications set by the standards, which allows the determination of some important parameters. Moreover, measurement of electrical properties (discussed in the following chapters) can also give relevant information about the quality of the biofuel. Both are useful alternatives for small- and medium-scale producers, as well as small research groups.