Toward improved heat transfer performance of annular heat exchangers with water/ethylene glycol-based nanofluids containing graphene nanoplatelets
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A novel synthesis procedure is presented for preparing functionalized graphene nanoplatelets (GNPs). Using sonication method, the functionalized GNPs are dispersed in water-ethylene glycol to prepare water–ethylene glycol-based functionalized GNP nanofluids. Meanwhile, the thermophysical properties of the prepared nanofluids, i.e., thermal conductivity, specific heat capacity, and rheological properties are investigated. As the second phase of study, the heat transfer performance of an annular channel is simulated and measured in the presence of the prepared nanofluids. To this end, a computational fluid dynamics study has been carried out to calculate the heat transfer rate as well as pressure drop of the well-dispersed nanofluids. Meanwhile, the effects of concentration and Reynolds number on the convective heat transfer coefficient have been investigated at constant wall temperature boundary condition under turbulent flow regime. Consist with the results, the convective heat transfer coefficient of nanofluids are significantly higher than that of the base-fluid. The novel type of nanofluid reveals promising potential for use as an advanced working fluid in future heat transfer applications.
KeywordsNanofluid Turbulent flow Forced convection flow Graphene Annular
List of symbols
Specific heat capacity at constant pressure (J kg−1 K−1)
Nanoparticle diameter (m)
Thermal conductivity (W m−1 K−1)
Nusselt number (h D λ−1)
Static pressure (N m−2)
Liquid Prandtl number
Heat flux (w m−2)
Velocity (m s−1)
Fluctuating part of velocity (m s−1)
Dynamic viscosity (kg m−1 s−1)
Density (kg m−3)
Particle volume fraction
The authors gratefully acknowledge University of Malaya Research Grants: RP012A-13AET, FP028-2014B, and High Impact Research Grant of UM.C/625/1/HIR/MOHE/ENG/45, as well as Faculty of Engineering, University of Malaya, Malaysia, for support to conduct this research work.
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