Abstract
Convection heat transfer coefficients and pressure drops of four functionalized graphene nanoplatelet nanofluids based on the commercial coolant Havoline® XLC Pre-mixed 50/50 were experimentally determined to assess its thermal performance. The potential heat transfer enhancement produced by nanofluids could play an important role in increasing the efficiency of cooling systems. Particularly in wind power, the increasing size of the wind turbines, up to 10 MW nowadays, requires sophisticated liquid cooling systems to keep the nominal temperature conditions and protect the components from temperature degradation and hazardous environment in off-shore wind parks. The effect of nanoadditive loading, temperature and Reynolds number in convection heat transfer coefficients and pressure drops is discussed. A dimensionless analysis of the results is carried out and empirical correlations for the Nusselt number and Darcy friction factor are proposed. A maximum enhancement in the convection heat transfer coefficient of 7% was found for the nanofluid with nanoadditive loading of 0.25 wt %. Contrarily, no enhancement was found for the nanofluids of higher functionalized graphene nanoplatelet mass fraction.
Highlights
IntroductionThermal processes play a major role in energy generation from both convectional fuels and renewable resources
Energy is one of the main resources for society nowadays
Particle addition to working fluids has been explored for several years and has become more and more relevant since Choi et al [1] suggested the use of nanoparticle dispersions, nanofluids, for heat transfer applications, taking advantage of the enhanced thermal conductivity of solids compared to the poor thermophysical properties of common working fluids
Summary
Thermal processes play a major role in energy generation from both convectional fuels and renewable resources. Thermal cycles, involving different heat transfer processes, are essential to transform energy, eventually converted into electricity in power plants from fossil and nuclear fuels, biomass or thermal solar energy. Given the importance of increasing the efficiency of heat transfer processes, several approaches have been investigated over the past years to enhance heat transfer such as vibration techniques, application of electric and magnetic fields or surface modification, among others. Particle addition to working fluids has been explored for several years and has become more and more relevant since Choi et al [1] suggested the use of nanoparticle dispersions, nanofluids, for heat transfer applications, taking advantage of the enhanced thermal conductivity of solids compared to the poor thermophysical properties of common working fluids
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