Specific heat experimental tests of simple and hybrid oxide-water nanofluids: Proposing new correlation

Nanofluids are on the top of the research interests of many groups due to their extraordinary heat transfer properties. Nevertheless, while the research was mainly focused on thermal conductivity and viscosity, another extremely relevant property, specific heat, remained little studied. Additionally, research is mainly directed towards alumina and carbon nanotubes based nanofluids, while silica and titania received little attention despite their very good applications and minimum environmental risks. This paper focuses on a complex experimental study on the specific heat of three oxide-water based nanofluids and two hybrid nanofluids. More precisely, alumina, titania and silica water based nanofluids were considered in volume concentrations in the range 0-3%. Results were in line with similar research and a new comprehensive correlation is proposed based on state of the art and experimental observations. In regard to hybrid nanofluids, rules of mixture can be an option to estimate the specific heat of hybrid nanofluids if the synergy between nanoparticles is satisfactory, while there is a strong need to intensify the studies on this topic (C) 2019 Elsevier B.V. All rights reserved.