بررسي مدلهاي رياضي ارائه شده براي محاسبه ضريب رسانش گرمايي نانوسيالات

Investigation of Nanofluids Thermal Conductivity Modeling

The pronounced heat transfer enhancement revealed experimentally in nanofluids suspensions is being investigated theoretically at the macro-scale level aiming at explaining the possible mechanisms that lead to such impressive experimental results. Recent measurements on nanofluids have demonstrated that the thermal conductivity increases with grain size. However, such increase can not be explained by existing theories. Four possible explanations have been suggestedfor this anomalous increase: Brownian motion of the particles, molecular-level layering of the liquid at the liquid-particle interface, the nature of heat transport in the nanoparticle, and the effects of nanoparticle clustering. These are shown to be the key factors in understanding thermal properties of nanofluids. These models show that the effective thermal conductivity is not only a function of the thermal conductivity of solid and liquid and their relative volume fraction, but also depends on the particle size and interfacial properties. Also the relative effects of nanoparticle motion mechanisms of dilute suspension, i.e., Brownian motion, thermo- phoresis and osmo-phoresis, including size dependence, on the thermal conductivity have been theoretically investigated and reported.