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.