Nanofluids can be obtained by dispersing nanometer-size solid particles in traditional heat transfer fluids such as water to increase thermal conductivity and heat transfer performance. Nanofluids have great advantages which can be followed from the properties of metallic or non-metallic particles that are added to base fluids. Most of nanofluids have been studied about experiments of thermal conductivity and mechanism of heat transfer enhancement. This study presents an experimental work on the convective heat transfer of nanofluids, made of CNC (Carbon Nano Colloid) and de-ionized water, flowing through a copper tube in the laminar flow condition. The results showed considerable enhancement of convective heat transfer using the CNC nanofluids at the concentration of 1.8 wt%. The local convective heat transfer coefficient of CNC nanofluids is maximum 18.8% higher than that of pure water. The enhancement was particularly significant in the fully developed region, and was much higher than that solely due to the enhancement on thermal conduction. It was also shown that the classical Shah equation failed to predict the heat transfer behavior of nanofluids. Migration of nanoparticles, and the resulting disturbance of the boundary layer were proposed to be the main reasons.
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