▎ 摘　　要

In this work, experimental study is performed to explore the cooling performance of water-based hybrid nanofluid with PCM and graphene nanoparticles in a tube to enhance energy efficiency of heat exchanger. The forced convection experiments have been performed for the cases of pure water and the hybrid nanofluids. The experiments are conducted for the volumetric flow rates of ((Q) over dot) = 60, 90 and 180 cm(3)/min, the mass fractions of tetracosane PCM nanoparticles of omega(pcm) = 2, 5, and 10%, and the mass fractions of graphene nanoparticles of omega(np) = 0 and 0.006%. The measured results show clearly that for the appropriate flow rate and heating power, using the nanoemulsion with the PCM nanoparticles as coolant can effectively reduce the wall temperature and enhance the heat dissipation effectiveness as compared with the case of pure water. However, the highly increased viscosity of the nanoemulsion with the PCM nanoparticles would drastically downgrade its highest figure of merit (FOM). The maximum average heat transfer effectiveness ratio of 1.044 can be achieved by using the PCM nanoparticles at l(h)(+) /(d(i)(+)Pe(f)) = 0.033, omega(pcm)/[Ste(f)* (1+Sb-f*)] ((Q) over dot) = 90 cm(3)/min. In addition, adding the graphene nanoparticles with the mass fraction of omega(np) = 0.006% to the nanoemulsion to form the hybrid nanofluid leads to significant enhancement in the heat transfer.