The measurement data, for which the moment of the force was less than 100 μNm, were rejected. The original electrorheological system designed for HAAKE MARS 2 is not equipped with any diagnostic tool allowing to determine whether the system is working properly. It is not possible to check whether the sample is actually located in an electric field or not. Furthermore, before each series
of measurements, the multimeter Rigol DM 3064 (Rigol, Beijing, China) was pinned to the rotor (Figure 4(D)). In this way, it was checked selleckchem whether the voltage is correctly supplied to the rotor, and we are sure that each sample was measured in an electric field. After completing all the calibration steps and finding that they were all carried out properly, the measurement of the earlier prepared sample was started. The sample of nanofluid with an automatic pipette on the lower measurement plate was applied, volume of the sample was 2.7 cm3. On the power supply unit, the desirable voltage was set, and then it was turned, Selleck NCT-501 thereby the
voltage to the rotor was brought. The first measurement was performed in the absence of voltage. Afterward, the sample has been tested for the following values of voltage: 500, 1,000, 1,500, and 2,000 V. The measurements of dynamic viscosity curves were performed in a step procedure in the CR mode at the shear range from 1 to 1,000 s −1 in the logarithmic scale. Each of the 30 steps took 100 s, wherein the value of the shear rate acting on the sample at that time was constant. The measurement points were collected on the basis of the results obtained in the last 3 s of a single step. In the course of measurements, it was not possible to maintain a constant temperature because an imposed mode of operation of the assembled system has made it impossible. A thixotrophic behavior was observed upon measurement in CR mode performed in three steps. First sample was measured with increase of shear rate from 1 to 1,000 s −1 in a time of 600 s. The second step was shearing the sample with a constant shear
rate of 1,000 s −1 used for 600 s. The third stage of experiment was the measurement with shear rate decreasing from 1,000 to 1 s −1 in 600 s. In view of the fact next that the measuring geometry was an air-cooled system, it was not possible to achieve a constant temperature during the measurements. The system was purged with air at room temperature, and the lab has efficient air conditioning system. Nevertheless, temperature spread reached 1.5°C. Results and discussion Pressure measurement A study to determine the dynamic viscosity curve of MgAl2O4-DG nanofluid under anisotropic high pressure was conducted. The experiment was performed on two samples of different mass concentrations of nanoparticles in nanofluid, namely 10 and 20 wt.%.