Heat Transfer Characteristics Study Of Self-prepared Graphene Nanofluids

Nanofluids as a new heat transfer working substance having already attracted significant attention recent years have the superiority such as high thermal conductivity etc., which is of great significance in the research of heat transfer. Most of the existing research concentrates upon how to prepare the nanofluids, how to keep it stable, and the physical property of nanofluids. The synthesis of the new graphene material which has the characteristics of high heat transmission coefficient was reported in this paper. After that, the graphene-ethanol nanofluids were obtained where the Polyvinyl Pyrrolidone was dispersant. The natural heat transfer and boiling heat transfer characteristic of the nanofluids were then analyzed by the numerical simulation.Ultrasonic exfoliation was employed to prepare graphene, the obtained solid was characteristiced by Raman Spectrum and Transmission Electron Microscope(TEM), which indicated the material is structurally stable and defectless. The stable graphene-ethanol nanofluids were then acquired. And the test of physical properties including thermal properties, rheological properties and wettability shows that the thermal conductivity increases with the volume fractio n of graphene nanoparticle, and the 0.1% nanofluids exhibited an improvement about 10% of the thermal conductivity. Besides, the viscosity of nanofluids enhances with the volume fraction of graphene nanoparticle as well, and the rheological properties of the nanofluids tallies with the newtonian fluid, which indicates the obtained nanofluids can be treat as newtonian fluid. In addition, the surface tension of the nanofluids increases with the volume fraction of nanoparticle as well as the surface contact angle.Convective heat transfer and boiling heat transfer are two typical heat transfer technology. Laminar flow model was primarily adopted to simulate the natural convection in a square cavity. After the verification of the veracity of the simulate method, the natural convection heat transfer of nanofluids with different volume fraction was numerical simulated. The consequence reveals that the nanofluids improve the convective heat transfer performance of the basefluid, and the convective heat transfer coefficient improve with the volume fraction of graphene, where the 0.1% nanofluids shows a 12% enhancement of the convective heat transfer coefficient.Euler-Euler two fluid model was adopted in the research of the pool boiling phenomena, it shows that nanofluids improve the boiling heat transfer performance of basefluid as well. The enhancement first increases then decreases with the increase of the volume fraction of nanoparticle. This is due to the enhancement of viscosity causes boiling crisis increasingly obvious when the volume fraction of nanoparticle is increasing, which offsets the effort of the improvement of the thermal conductivity.