The objective of this research is to improve understanding of
the effect of nitrogen-doped graphene (NDG) nanofluids concentration
on the convective heat transfer coefficient and the friction
factor under laminar flow, through experimental investigations.
Such research on the convective heat transfer of NDG nanofluids
in heat transfer systems is required for several reasons: (a) the convective
heat transfer of NDG nanofluids has not been previously
investigated, and (b) NDG has a high thermal conductivity and
can improve the heat transfer coefficient of the base fluid. The
NDG synthesized by heat treatment of graphene in an ammonia
solution is followed by the preparation of stable nanofluids with
desired characteristics. The present study examines the characteristics
of NDG nanosheets and the stability, thermal conductivity,
and viscosity of NDG nanofluids at several concentrations (0.01,
0.02, 0.04 and 0.06 wt%) with Triton X-100 as a surfactant. The
variation of the convective heat transfer coefficient is investigated
under heat fluxes of 3.5 kW/m2 and an inlet temperature of 30 C
at various concentrations of NDG nanofluid under several bulk
velocities ranging from 0.05 to 0.4 m/s (for which the Reynolds
number varies from 290 to 2300).