Convective heat transfer characteristics of water–ethylene glycol mixture with silver nanoparticles

• Thermal properties and heat transfer coefficient of Ag nanofluids are reported.
• Thermal diffusivity increases linearly with silver volume fraction.
• Maximum enhancement of 42% in heat transfer coefficient was obtained.
• Pressure drop increases significantly beyond 0.15 vol% of Ag loading.
• Ag nanofluid is favorable for engineering applications up to 0.15 vol%.

We report the convective heat transfer characteristics of water–ethylene glycol mixture fluids seeded with silver nanofluids under laminar, transitional and turbulent regime in this work. The volume concentrations of silver nanoparticles viz. 0.05%, 0.1%, 0.15%, 0.3% and 0.45% are considered. Thermophysical properties measurements such as thermal conductivity, viscosity, density and specific heat capacity were carried out using conventional techniques. Convection measurements were carried out in a tube in tube counter flow heat exchanger using nanofluids as the hot fluid. The effect of nanofluid mass flow rate ranging from 5 g/s to 45 g/s and inlet temperature of nanofluid at 35 °C and 45 °C on the convective heat transfer coefficient were investigated. The convective heat transfer coefficient was considerably increased with increasing Reynolds number, particle concentration and inlet temperature. The maximum enhancement of convective heat transfer coefficient of nanofluid is observed to be ∼42% at 0.45 vol% compared with pure basefluid. The pressure drop of nanofluid increases marginally for a nanofluid volume concentration up to 0.15 vol%. When compared with the base fluid, the difference of pressure drop is insignificant so that the use of nanofluid has limited penalty on the pressure drop up to 0.15 vol% loading of silver nanoparticles. However, beyond 0.15 vol% the pressure drop increases significantly which limits the use of these nanofluids at higher concentration for engineering applications.

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