Experimental study of transition flow from single phase to two phase flow boiling in nanofluids

In this paper, behavior of low concentration nanofluids (0.1%, 0.5%, 2.5% by vol.) is experimentally studied in a circular channel subjected to a constant heat flux. Two average particle sizes (10 and 20 nm) were also used. The local heat transfer coefficient is measured for water-based nanofluids containing oxide nanoparticles (TiO2, Al2O3, CuO) under the single phase regime and subcooled flow boiling conditions in a vertical channel. In single phase regime, it is found that the convective heat transfer coefficient enhances for nanofluids. Nucleate boiling augmented the rate of heat transfer. However, at the subcooled regime, the rate of heat transfer degrades for nanofluids and it degrades more by increasing concentration of nanoparticles. On the other hand, it can be seen the nanoparticle type has a small effect on this degradation, while the particle size has more effect on heat transfer coefficient variation. Comparisons with correlations present in literature are accomplished and a very good agreement is realized.