A thermal conductivity model for nanofluids including effect of the temperature-dependent interfacial layer (original) (raw)
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A Review of Thermal Conductivity Models for Nanofluids.
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Nanofluids, containing nanometric metallic or oxide particles, exhibit extraordinarily high thermal conductivity that can be used for enhancing heat transfer performance of conventional systems. This work presents a proposed method for calculating the effective thermal conductivity of nanofluids. The thermal conductivity of nanofluids primarily depends on the properties of base fluids and nanoparticles, the volume fraction of nanoparticles, the interfacial layer, non-uniform sizes of nanoparticles, fractal dimension of particles, Brownian motion and temperature. In the resent study, the impact of non-uniform sizes of nanoparticles and interfacial layer is investigated simultaneously. Hence, this model has the capability of offering both analytical and numerical Predictions. Results of the present model show reasonably good and better agreements with available experimental data.
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Traditional heat transfer fluids which are used in various applications such as chemical processes, refrigeration, heating and cooling processes, transportation, power generation and other micro-sized applications have poor heat transfer properties and impose limitation to heat transfer augmentation. Thermo-physical properties of conventional fluids play an important role in the development of energy efficient heat transfer equipment. The poor thermal conductivity limits their performance. Improving the thermal conductivity is the key idea to improve the heat transfer characteristics of conventional fluids. Since a solid matrix has a larger thermal conductivity relative to base fluid, suspending solid fine particles (millimeter or micrometer sized range) into the base fluid is expected to improve the thermal conductivity. A dilute suspension of nanometer-sized particles dispersed in a base fluid is known as Nanofluids. Nanofluids exhibit enhanced heat transfer properties and are exp...
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In this study two appropriate semi-experimental models based on none-linear regression over 800 extracted experimental data to predict the thermal conductivity coefficient of nanofluids were presented. Here, the used nanofluids were spherical nanoparticles of Al2O3, TiO2, CuO, ZnO, ZrO2, CeO2, MgO, SiO2, Fe2O3, Fe3O4, Al, Cu, Fe, Ag, SiC and diamond dispersed in water, ethylene glycol, radiator coolant and various oils as base fluids. The thermal conductivity coefficient of particles and base fluid, temperature in the range of 10–80 °C, volume fraction from 0.04% to 14% were considered as effective parameters to develop first model (model 4-P), whereas, the second model were presented by taking the effect of particle diameter from 4 to150 nm into account (model 5-P). The mean square error and correlation coefficient were found to be 0.00059 and 0.9939 for 4-P model, and 0.000548 and 0.9944 for 5-P model, respectively, for all data. The highest error of the predicted value using mode...
Review on Thermal Conductivity of Nanofluids
Among the thermo physical properties of the nano fluids thermal conductivity is the key property which depends on the pertinent parameters of nanoparticles material, volume fraction, size, aspect ratio, base fluid thermo physical properties, temperature, and surfactant. Over last decades, numerous works have reported the higher thermal conductivity of nano fluids than that of the conventional heat transfer fluids with the reason of random motion of nanoparticles and a number of numerical and theoretical models have been proposed. In this article, the current state of knowledge on the several thermal conductivity measurement techniques employed by the researchers along with the factors affecting the thermal conductivity of nano fluids have been presented. This review leads to some directions for future research in nano fluids.