Natural convection heat transfer characteristics of TiO2–H2O nanofluids in a cavity filled with metal foam

In this paper, TiO2–H2O nanofluids are used instead of traditional mediums such as water and oil as the heat transfer medium. For the purpose of research on the natural convection heat transfer characteristics of TiO2–H2O nanofluids in a cavity filled with metal foam, a natural convection experiment system filled with different pore density (PPI) copper foam was established. The experimental results showed that the filling of the metal foam greatly improves the heat transfer effect in the cavity. When the PPI of the metal foam copper is 5 and 25, the Nusselt numbers are similar and larger than that of PPI = 15. The heat transfer effect of water in a cavity with the PPI = 5, PPI = 15 and PPI = 25 metal foam can be enhanced by 58.8%, 31.4% and 63.3% compared with that without metal foam, respectively. The heat transfer effect increases with the concentration of nanofluids. TiO2–H2O nanofluids with 0.1%, 0.3% and 0.5% mass fraction can enhance heat exchange by 6.3%, 22.9% and 32.1% compared with water, respectively. In addition, as the heating power increases, the heat transfer is improved while the heat transfer enhancement efficiency deteriorates.