Performance of water based CuO and Al₂O₃ nanofluids in a Cu–Be alloy heat sink with rectangular microchannels

Highlights: • 0.2 vol.% CuO nanofluids enhanced the heat transfer coefficient up to 27%. • 1 vol.% Al₂O₃ nanofluids enhanced the heat transfer coefficient up and 49%. • Both nanofluids showed larger pressure drop in comparison with pure water. • Nanofluid effect may be deteriorated due to deposition at higher flow rates. • Large heat transfer coefficient and small Nu number is a feature of MCHS. - Abstract: Single phase forced convective heat transfer and fluid flow of CuO/water and Al₂O₃/water nanofluids have been experimentally investigated in a microchannel heat sink (MCHS). The heat sink consisted of 17 rectangular cross section microchannels with the dimensions of 400 μm × 560 μm. All the experiments have been performed at constant heat flux of 19 W/cm² and at the laminar flow regime 500 < Re < 2000. Heat transfer coefficient, Nu number, and also pressure drop in the MCHS have been measured and compared with the conventional correlations. Both nanofluids showed greater heat transfer performance and larger pressure drop in comparison with pure water. Results indicated that 0.2 vol.% CuO and 1 vol.% Al₂O₃ nanofluids enhanced the heat transfer coefficient up to 27% and 49%, respectively. In this regards, CuO nanoparticle was more efficient since it could be used in lower concentration. Furthermore, it was shown that the heat transfer coefficient increased with increasing the nanoparticle concentration but it was not true to say that the heat transfer enhancement increased with Reynolds number. The results of this study in conjunction with previous papers indicated that lower Nu numbers and higher heat transfer coefficients would be obtained in the MCHS in comparison with the conventional diameter heat exchangers. It showed the greater importance of both conductive and convective heat transfer mechanisms in this kind of heat exchangers