Thermal Conduct ivity and Thermal Diffusivity of Biodiesel and Bioethanol Samples

This article deals with thermal properties of selected biodiesel and bioethanol samples (biodiesel No 1, No 2 and bioethanol No 1, No 2). Biodiesel is renewable fuel that can be manufactured from vegetable oils, animal fats, or recycled restaurant grease for use in diesel vehicles. Biodiesel‘s physical properties are similar to those of petroleum diesel, but it is a cleaner-burning alternative fuel. Ethanol (CH3CH2OH) is a clear liquid. Also known as ethyl alcohol, grain alcohol, and EtOH, the molecules in this fuel contain a hydroxyl group (OH-) bonded to a carbon atom. Ethanol is made of the same chemical compound regardless of whether it is produced from starch and sugar-based feedstocks, such as corn grain, sugar cane, etc. The hot wire method was used for thermal parameters measurements. The experiment is based on measuring the temperature rise vs. time evaluation of an electrically heated wire embedded in the tested material. Thermal conductivity is derived from the resulting change in temperature over a known time interval. For two samples of biodiesel and two samples of bioethanol, there were determined basic thermophysical parameters – thermal conductivity and thermal diffusivity. Two series of measurements were made for each sample of biodiesel and bioethanol. In the first series, there were measured the thermal conductivity and thermal diffusivity at constant room temperature 20 °C. Every thermophysical parameter was measured 10 times for each sample. The results were statistically processed. In the second series of measurements, there were measured the relations of thermal conductivity and thermal diffusivity to temperature in temperature range 20–29 °C. It was evident from results that all measured dependencies are nonlinear. Polynomial functions described by polynomial coefficients were obtained for both thermophysical parameters. The type of function was selected according to statistical evaluation based on the coefficient of determination for every thermophysical parameter graphical dependency. All obtained results are presented in Figures 1–4 and in Tables 1–4. The results of thermophysical parameters measurements of biodiesel and bioethanol could be compared with the values presented in literature.