Effects of hybrid nanofluid mixture in plate heat exchangers

•Heat transfer and pressure drop of a hybrid nanofluid mixture were studied.•Heat transfer enhancement was observed for the hybrid nanofluid mixture.•A small pressure drop penalty was observed for the hybrid nanofluid mixture.

Heat transfer and pressure drop characteristics of a hybrid nanofluid mixture containing alumina nanoparticles and multi-walled carbon nanotubes (MWCNTs) were experimentally investigated in a chevron corrugated-plate heat exchanger. A MWCNT/water nanofluid with a volume concentration of 0.0111% and an Al2O3/water nanofluid with a volume concentration of 1.89% were mixed at a volume ratio of 1:2.5. A small amount of MWCNTs was added in order to increase the mixture thermal conductivity. Experiments with water used as both hot and cold fluids were carried out first to obtain a heat transfer correlation for fluids flowing in the chevron plate heat exchanger. The results of the nanofluid mixture were compared with those of the Al2O3/water nanofluid and water. Results show that the heat transfer coefficient of the hybrid nanofluid mixture is slightly larger than that of the Al2O3/water nanofluid and water, when comparison is based on the same flow velocity. The hybrid nanofluid mixture also exhibits the highest heat transfer coefficient at a given pumping power. The pressure drop of the hybrid nanofluid mixture is smaller than that of the Al2O3/water nanofluid and only slightly higher than that of water. Therefore, hybrid nanofluid mixtures might be promising in many heat transfer applications.