computational analysis of hybrid nanofluid flow in a double-tube heat exchanger: a numerical study

The heat transfer improvement and the increase of heat exchangers’ efficiency represent a very important issue in the energy field. many research projects have focused on the use of fluids with high thermal conductivity such as nanofluids. in this case, hybrid nanofluids, are a new class of nanofluids with good heat transfer characteristics. the present work falls within this framework and involves a numerical study to examine the influence of two oil-based hybrid nanofluids, al2o3-mwcnt and mgo-mwcnt, with different volume concentrations and inlet flow rates. more to the point, the impact of different nanoparticle ratio and the location of hybrid nanofluid in a laminar flow of two-pipe counter-current heat exchanger have been investigated. in virtue of which, the results illustrate that increasing the volume concentration of nanoparticles and the flow rate of the hybrid nanofluid has a positive impact on improving the heat transfer rate. therefore, the improvement in heat transfer rate reached 77.8% for al2o3-mwcnt/oil hybrid nanofluid and 59.5% for mgo-mwcnt/oil hybrid nanofluid. similarly, the study has also revealed that the preferred nanoparticles ratio for al2o3-mwcnt/oil hybrid nanofluid is in the order of (25:75) and its circulation in the inner tube as a hot fluid makes it possible to improve the thermal performance of the considered two-tube heat exchanger to a greater advantage.