Experimental Study On Quenching Boiling Of An Aqueous Suspension With Graphene Oxide Nanosheets

In this paper, the boiling heat transfer characteristics of an aqueous suspension with graphene oxide nanosheets (GONs) was investigated using the transient quenching method for large container, and the boiling curve and the critical heat flux of the entire quenching process of the GONs suspensions was obtained by the zero-dimensional model based on the assumption of the lumped parameter. A three-step dilution method was used to prepare five different concentrations (mass fraction ranging1-100ppm) of GONs suspensions, which was characterized by UV-Vis spectrometer instrument, scanning electron microscopy and transmission electron microscopy to insure the stability in the experiment.To clarify the boiling heat transfer characteristics of different concentrations of GONs suspensions quenched at different roughness, different kinds of metals and different quenching times, a series of experiments were compared, and the results are as follows:For the smooth surface of the nickel-plated copper ball, the addition of different concentrations of GONs particles in the working fluid could accelerate the quenching rate, and the boiling critical heat flux (CHF) is also improved. The fasted quenching process was observed in the3rd quenching with100ppm, and the quenching time is39%shorter than that of in the pure water. The maximum CHF was observed in the3rd quenching with50ppm, which is about110%of that of the pure water.For different nickel-plated copper balls, the trend of the quenching rate is relevant to the concentrations with increasing the roughness. At20ppm, the fasted quenching process was observed after surface M4quenched6times in sequence in the GONs suspensions and then quenched in the D1water, and the quenching time is39%shorter than quenched in the water. The maximum CHF of the M4surface is obtained in the5th quenching, which is118%of that of in the water. At10ppm, the fasted quenching process was observed after surface M3quenched4times in sequence in the GONs suspensions and then quenched in the DI water, and the quenching time is18%shorter than quenched in the water. The maximum CHF of the P surface is obtained in the2nd quenching, which is enhanced by118%.For different plated materials on the copper ball surface at1ppm, the enhancement of the quenching rate and CHF of the quenched copper ball surface is more pronounced than that of the nickel surface. The fasted quenching of the quenched copper surface is obtained in the2nd quenching in the suspensions, which is about92s, and the maximum CHF is enhanced by about121%than that of quenched in the DI water.We could speculate from the experimental results that successive deposition of nanoparticles leads to the structure change of the boiling surface, with increasing quenching time, a certain surface structure could enhance the boiling heat transfer, which is named as the suitable quenching surface (because the quenching is the fastest). The observation of the suitable quenching surface could be very important to the acceleration in the quenching processes such as the heat treatment of materials in real application.