Original scientific paper


2013, 14 (3)   p. 1132-1143

Monika Božiková, Peter Hlaváč


This article deals with thermal properties of selected biooils (Plahyd S – biooil No1 and Plahyd N – biooil No2) and rheologic properties of rapeseed oil. Plahyd S is a synthetic, rapidly biodegradable fluid which is based on sustainable raw materials. It is exceptionally suitable for applications in mobile and stationary hydraulic systems. Plahyd N is multigrade hydraulic oil based on rapeseed oil used in agricultural and construction machinery. For thermal parameters measurements was used Hot wire method. The experiment is based on measuring of the temperature rise vs. time evaluation of an electrically heated wire embedded in the tested material. The thermal conductivity is derived from the resulting change in temperature over a known time interval. Dependency of material resistance against the probe rotation was used at measurement of rheologic properties with instrument viscometer Anton Paar DV-3P. For two samples of biooils – Plahyd N and Plahyd S were determined basic thermophysical parameters – thermal conductivity, thermal diffusivity and volume specific heat. For each biooil samples were made two series of measurements. In the first series were measured 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. For biooil No1 thermal conductivity was 0.325 W*m -1 .K-1 , it was higher value than we obtained for biooil No2 – 0.224 W*m -1 .K-1 . The similar results were obtained for thermal diffusivity of biooil No1 2.140.10-7 m 2 *s -1 and biooil No2 2.604.10-7 m 2* s -1 . For samples with constant temperature were calculated basic statistical characteristics as: standard deviation for  – biooil No1 (±0.056 W*m -1*K -1 ) and biooil No2 (± 0.054 W*m -1*K -1 ); probable error of the arithmetic average for  – biooil No 1 (±0.012 W*m - 1*K -1 ) and biooil No 2 (±0.005 W*m -1*K -1 ); relative probable error in % for  – biooil No1 (±3.69 %) and biooil No2 (±2.23 %). The same statistical characteristics were calculated for thermal diffusivity. In the second series of measurements were measured relations of thermal conductivity and thermal diffusivity to the temperature in temperature range (20 – 29) °C. From results was evident that all measured dependencies are nonlinear. For both thermophysical parameters were obtained polynomial functions of the second degree described by the polynomial coefficients. Type of function was selected according to statistical evaluation based on the coefficient of determination for every thermophysical parameter graphical dependency. In temperature dependency of rapeseed oil dynamic viscosity was used decreasing exponential function, which is in accordance with Arrhenius equation. The results obtained by the implementation of thermophysical and rheologic measurements on samples of biooils could be compared with the values presented in the literature.


biooils, dynamic viscosity, temperature, thermal conductivity, thermal diffusivity

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