Role of nanoparticles on boiling heat transfer performance of ethylene glycol aqueous solution based graphene nanosheets nanofluid

As the ethylene glycol aqueous solution (EG/DW) with a volume fraction of 60:40% (the ratio of ethylene glycol (EG) and deionized water (DW)) was widely used as an antifreeze solution, pool boiling heat transfer (BHT) characteristics including boiling heat transfer coefficient (HTC) and critical heat flux (CHF) of EG/DW based graphene nanosheets (GNs) nanofluids are experimentally investigated under atmospheric pressure. The influence of heat flux and nanoparticles mass fraction on the boiling heat transfer has been measured and discussed. Boiling curves were obtained for the nanofluids compared with the baseline case of EG/DW. It was shown that for low concentration (i.e., mass fraction up to 0.02%) GNs-EG/DW nanofluids, the boiling performance of the EG/DW had been obviously enhanced by adding GNs nanoparticles, which was resulted from the enhancement of surface wettability caused by nanoparticles deposition. However, further loading GNs in EG/DW reduced the BHT capability of EG/DW, results from the GNs sedimentation and subsequent blockage of the nucleation sites. At the small concentration less than 0.02%, the CHF rapidly increases with increasing nanoparticle concentration. However, the CHF magnitude is almost the same for GNs-EG/DW nanofluids with concentration beyond the critical concentration.