The quenching behavior of aqueous nanofluids around rods with high temperature

The quenching behavior of aqueous nanofluids containing various volume fractions of Al2O3, SiO2, TiO2 and CuO nanoparticles is experimentally investigated around high temperature brass rod (diameter 20 mm × 75 mm). The experiments are performed at saturated conditions under atmospheric pressure. The results show that the quenching process is strongly dependent on the kind of nanoparticle, as well as its volume fraction. Although it is not observed from the first run in nanofluids, the quenching time is considerably shortened during the repetitive quenching tests. After the repetition tests in nanofluids, a nanoparticles porous layer occurs on the quenched surface and thus, the film boiling vanishes. The surface contact angles and the surface roughness of the quenched surfaces are measured. The results show that contact angles decreases and the surface roughness increases. It can be concluded that the primary reason of critical heat flux enhancement is the change of the surface characteristics due to the porous layer. In addition, the results also showed that there is no significant change in the nucleate boiling heat transfer.