THERMOPHYSICAL AND RHEOLOGIC PROPERTIES OF BIOOIL SAMPLES

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

INFLUENCE OF STORING AND TEMPERATURE ON RHEOLOGIC AND THERMOPHYSICAL PROPERTIES OF WHISKY SAMPLES

Temperature and storing time can be included between the most significant parameters that influence physical properties of food. This article deals with selected rheologic and thermophysical properties of alcohol drink whisky. Our research was oriented on measuring of rheologic and thermophysical characteristics of whisky. There were measured two types of whisky – Grant’s and Jim Beam from two different producers, both samples had 40 % of alcohol content. During the experiments were analyzed rheologic parameters as: dynamic viscosity, kinematic viscosity and fluidity and thermophysical parameters as: thermal conductivity, thermal diffusivity and volume specific heat. Selected parameters were measured in temperature range (-5 – 27) °C. Measurements were done on whisky samples in different days during the storage. Measuring of dynamic viscosity was performed by digital rotational viscometer Anton Paar (DV-3P). Principle of measuring is based on dependency of sample resistance against the probe rotation. Density of whisky samples was determined by pycnometric method. Average density at given temperature along with dynamic viscosity value was used at calculation of kinematic viscosity and fluidity was also determined. Measuring of thermophysical parameters was performed by instrument Isomet 2104. Measurement by Isomet is based on analysis of the temperature response of the measured sample to heat flow impulses. Relations of rheologic and thermophysical parameters to the temperature were made and influence of storing time was discussed. From obtained results is clear that dynamic and kinematic viscosity is decreasing exponentially with temperature and fluidity has increasing exponential progress. We found out that both whisky samples had at the beginning and after one week of storage very similar values of rheologic parameters. Very small difference in rheologic parameters of whisky samples was found after two weeks of storing. Values of dynamic and kinematic viscosity were a bit higher and values of fluidity were a bit smaller after storing, that can be caused by loosening of the water during storage. Thermophysical parameters are increasing linearly with temperature for both whisky samples. Higher values of thermophysical parameters were in all cases obtained for whisky Grant’s