Performance of an agitated helical coil heat exchanger using Al2O3/water nanofluid

•The performance of coil heat exchanger is evaluated using Al2O3/water nanofluid.•Energy savings are determined when the nanofluid is used as heating medium.•Percentage energy savings are more in laminar and turbulent flow compared to transition flow.•Highest energy savings of 10.65% have been obtained. The performance of an agitated helical coil heat exchanger using Al2O3/water nanofluid has been evaluated in terms of the energy consumed to heat another fluid. The comparison has been made when nanofluid and base fluid (water) are used as heating medium. The studies have been carried out using Al2O3/water nanofluid of different concentrations, flow rates, stirrer speeds and shell-side fluid (heating medium) temperatures. It has been observed that, energy savings are more in laminar and turbulent conditions of flow than transition regime, and percentage savings increase with increase in nanoparticle concentration. Higher stirrer speed and shell-side fluid temperature also resulted in more energy savings. In addition, use of nanofluid resulted in heating the coil-side fluid (water) to higher outlet temperature. Maximum energy savings of 10.65% have been obtained in the presentstudy.