Heat transfer enhancement of ZnO–ethylene glycol nanofluids was studied.

Nanofluids' physical properties were studied at different temperatures up to 70 °C.

2.5 wt.% ZnO nanofluids enhanced the heat transfer coefficient up to 30%.

Heat transfer may be deteriorated due to deposition at higher particle fractions.

Nanoparticles in different flow regimes have different effects on the pressure drop.