Nanofluids spray heat transfer enhancement

Spray cooling experiments were carried out to study the effect of seven (7) different types of nanofluids on heat transfer enhancement. Three different concentrations of 0.04%, 0.07%, and 0.1% by volume of Ag, Al, Al2O3, Fe3O4, SiO2, TiO2 and multi-walled carbon nanotubes (MWCNTs) dispersed with deionized (DI) water were tested, and transient as well as steady spray boiling experiments were conducted over a copper flat plate heater 4 cm2 in size with a 1 cm thickness. The spray was issued by a 270 μm full-cone nozzle with a spray height of 30 mm and a spray mass flux of 1.5 × 10−3 kg/cm2 s. Both a transient cooling curve and steady boiling curve were obtained. The results revealed that the average heat transfer coefficient (HTC), as well as the associated critical heat flux (CHF), are significantly enhanced, and the enhancement ratio can be up to 1.7 (HTC) and 1.84 (CHF), respectively, corresponding to the DI water as the nanofluids' volume fraction increased from 0.04% to 0.1%.