Narrow Results

The present work involves in determining isotropic and effective pair potential energy of binary gas mixtures of Kr–Xe, Kr–C₂H₆, Xe–C₂H₆, Kr–C₃H₈, and Xe–C₃H₈ from thermophysical properties consisting of viscosity and second virial coefficients through inversion method. Typically, the calculated intermolecular potential energy of Kr–Xe system has compared with HFD model potential reported in literature. A desirable harmony between our model potential and HFD model has been obtained. In order to assess the potential energies obtained, transport properties including viscosity, diffusion, thermal diffusion factor, and thermal conductivity of aforementioned mixtures were predicted using the calculated models potential. The deviation percentage of the calculated viscosity and thermal conductivity of above-mentioned mixtures from the literature values are, respectively, within ±2%, ±3%.

The influence of particle size on density, ultrasonic velocity and viscosity of magnetite nanofluids have been determined at (298.15 K, 303.15 K, 308.15 K and 313.15 K). Two different sized nanoparticles (commercially procured D = 20–30 nm and synthesized D = 9 ± 3 nm in the laboratory by co-precipitation method) were dispersed in a citric acid base fluid. The desired parameters have been experimentally determined by loading different concentrations of nanoparticles. It has been found that the influence of particle size and temperature on measured physical parameters (density, ultrasonic velocity and viscosity) is not negligible and can also be taken into account in any practical application. The analyzed physical parameters can describe qualitatively and quantitatively the particle size distribution of nanofluids at a specific temperature. Results are interpreted in terms of particle–particle and particle–fluid interactions.

In the present study, the effect of particle concentration, particle diameter and temperature on the thermal conductivity and viscosity of Al₂O₃/water nanofluids was investigated experimentally using design of experiment approach (full factorial design). Variables were selected at two levels each: particle concentration (0.1–1%), particle diameter (20–40nm) and temperature (10–40${}^{\circ }$C). It was observed that the thermal conductivity of the Al₂O₃/water nanofluids increases with increasing concentration and temperature and decreases with increase in particle diameter, while viscosity increases with increasing particle diameter. Results showed that the interaction effect of concentration and temperature also has significant effect on the thermal conductivity of Al₂O₃/water nanofluids. For viscosity, the interaction of particle diameter and temperature was important. Utility concept was used to optimize the properties collectively for better heat transfer performance. The optimal combination for high thermal conductivity and low viscosity was obtained at higher level of particle concentration (1%), lower level of particle diameter (20nm) and higher level of temperature (40${}^{\circ }$C). At this condition the increment in thermal conductivity and viscosity compared to base fluid was 11.51% and 6.37%, respectively.