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In an effort to enhance heat transfer in the laminar flow regime of a heating duct, TiO2 and SiO2 nanoparticles were added to water to create nanofluids with a higher thermal conductivity than that of the water alone. Twist-tape was also used to enhance heat transfer within the duct. The thermal conductivities of the nanofluids were measured using the Transient Plane Source instrument. It was found that the use of twist tape alone gave a significant enhancement of convective heat transfer in the laminar flow, but that the use of nanofluids further enhanced the heat transfer.
This article studies the effect of dispersion of Cu2O nanoparticles on the thermoelectric properties of Ba0.4Co4Sb12 and Sn0.4Ba0.4Co4Sb12 skutterudites. It was found that the dispersion of these nanoparticles resulted in an increased thermoelectric efficiency due to decreased electrical resistivity and thermal conductivity. The figure of merit for Cu2O dispersed Ba0.4Co4Sb12 reached a maximum value of 0.92 at 573 K. This value represents a greater than 200% increase when compared to the pure matrix.
Two series of nanofluids were prepared by the researchers, using water as the carrier fluid, and Al2O3 and TiO2 as the nanoparticles; up to 6% particle volume fraction was used. The thermal conductivity and thermal diffusivity of the nanofluids were measured using the Transient Plane Source, TPS technique, and dynamic viscosity was also measured. The amount of nanoparticle volume fraction affected the value of thermal conductivity, but the nanoparticle cluster size did not have a significant impact. The nanofluids were studied from 1 to 40°C, and it was determined that the Al2O3 nanofluid exhibited more desirable thermal properties than the TiO2 nanofluid.
Al2O3 nanofluids were prepared with 2, 3, and 4 vol% Al2O3 nanoparticles in water for use as a coolant in plate heat exchangers. Using the Transient Plane Source, TPS technique, the thermophysical properties of the nanofluids were studied. Correlation equations were obtained for Nusselt number and the friction factor for the nanofluids and water. Less nanofluid is required to produce the same amount of cooling than water.
Through the addition of copper oxide nanoparticles to cyclohexane in varying concentrations, a series of nano-enhanced phase change materials (NePCM) were prepared. The Transient Plane Source, TPS technique was used to characterize the NePCM at multiple temperatures. It was determined experimentally that increasing concentrations of nanoparticles in the liquid phase resulted in increasing thermal conductivity, but increasing nanoparticle concentration in the solid phase didn’t have the same effect.Unidirectional freezing was also investigated.
