Laminar convective heat transfer and viscous pressure loss of alumina–water and zirconia–water nanofluids

Laminar convective heat transfer and viscous pressure loss were investigated for alumina–water and zirconia–water nanofluids in a flow loop with a vertical heated tube. The heat transfer coefficients in the entrance region and in the fully developed region are found to increase by 17% and 27%, respectively, for alumina–water nanofluid at 6 vol % with respect to pure water. The zirconia–water nanofluid heat transfer coefficient increases by approximately 2% in the entrance region and 3% in the fully developed region at 1.32 vol %. The measured pressure loss for the nanofluids is in general much higher than for pure water. However, both the measured nanofluid heat transfer coefficient and pressure loss are in good agreement with the traditional model predictions for laminar flow, provided that the loading- and temperature-dependent thermophysical properties of the nanofluids are utilized in the evaluation of the dimensionless numbers. In other words, no abnormal heat transfer enhancement or pressure loss was observed within measurement errors.