Experimental investigation on the stability and thermophysical properties of Al2O3/DW and CuO/DW nanofluids to be utilized in an indirect water bath heater

In this paper, 0.5–5 mass/% of Al2O3 and CuO nano-additives were dispersed in the base water by the two stage method (with a magnetic stirrer and ultra-sonication bath) to prepare different nanofluids with enhanced thermophysical properties. These nanofluids are considered to be utilized, as the bath fluid in the shell side of an indirect water bath heater to improve the thermal performance and reduce the power consumption of the heater. The effects of ultra-sonication time, surfactants, and nanoparticle size on the well formation of nanofluids, and their stabilities were probed. Densities, shear stresses, and apparent viscosities of the nanofluids were also measured to investigate the non-Newtonian behavior of samples. In addition, effects of the temperature, PH, nanoparticle type and concentration, and nanoparticle sizes on the thermal conductivities of nanofluids were investigated. Finally, nanofluids were utilized in a large-scale indirect water bath heater and its power consumption reduction compared to that of using water, as the bath fluid was measured and reported. 5 mass/% of CuO/water nanofluid at 80 °C was found the best nanofluids with the thermal conductivity enhancement of 43.28% and heater power consumption reduction of 17.1%.