Abstract
Experimental data are presented for the thermal conductivity, viscosity, and turbulent flow heat transfer coefficient of nanofluids with SiC particles suspended in ethylene glycol (EG)/water (H2O) mixture with a 50/50 volume ratio. The results are compared to the analogous suspensions in water for four sizes of SiC particles (16–90 nm). It is demonstrated that the heat transfer efficiency is a function of both the average particle size and the system temperature. The results show that adding SiC nanoparticles to an EG/H2O mixture can significantly improve the cooling efficiency while water-based nanofluids are typically less efficient than the base fluids. This is one of the few times that substantial nanofluid heat transfer enhancement has been reported in the literature based on a realistic comparison basis of constant velocity or pumping power. The trends important for engineering efficient heat transfer nanofluids are summarized.
Highlights
The majority of the studies were conducted for water based fluids, one of the nature’s best heat transfer fluids due to a favorable combination of high thermal conductivity and low viscosity
We previously investigated water-based SiC nanofluids5,6 and found that the increases in the thermal conductivity were significant but the increase in the viscosity with the introduction of the nanoparticles resulted in the heat transfer coefficient being up to 15% worse than that of the base fluid
Adjusting the pH and using larger particle sizes can significantly decrease the viscosity of suspensions but for SiC– H2O the nanofluid heat transfer coefficient was still just slightly above that of pure water6,7 at a constant velocity in fully developed turbulent flow
Summary
The interest in nanofluids as potential heat transfer fluids spiked initially due to very promising results on the enhanced thermal conductivity for a nanofluid containing copper in pump oil but was disclaimed later when multiple research groups tested a variety of available combinations of fluids and nanoparticles primarily at room temperature. The majority of the studies were conducted for water based fluids, one of the nature’s best heat transfer fluids due to a favorable combination of high thermal conductivity and low viscosity. The majority of the studies were conducted for water based fluids, one of the nature’s best heat transfer fluids due to a favorable combination of high thermal conductivity and low viscosity. Adjusting the pH and using larger particle sizes can significantly decrease the viscosity of suspensions but for SiC– H2O the nanofluid heat transfer coefficient was still just slightly above that of pure water at a constant velocity in fully developed turbulent flow.. Adjusting the pH and using larger particle sizes can significantly decrease the viscosity of suspensions but for SiC– H2O the nanofluid heat transfer coefficient was still just slightly above that of pure water at a constant velocity in fully developed turbulent flow.8 It was shown in several studies that the base fluids with the higher viscosity and lower thermal conductivity benefited most from the addition of nanoparticles Adjusting the pH and using larger particle sizes can significantly decrease the viscosity of suspensions but for SiC– H2O the nanofluid heat transfer coefficient was still just slightly above that of pure water at a constant velocity in fully developed turbulent flow. It was shown in several studies that the base fluids with the higher viscosity and lower thermal conductivity benefited most from the addition of nanoparticles
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