MWCNT/water nanofluid flow in a double pipe U-bend heat exchanger. The experiments were conducted at
different Reynolds number (3500–12000) and particle volume concentrations (0.05%–0.3%). The thermal
conductivity and viscosity are augmented by 15.27% and 9.15% at a temperature of 70 ◦C with respect to water
data. The Nusselt number, heat transfer coefficient, thermal performance factor are enhanced by 31.3%, 44.17%,
and 25.5% at a particle concentration of 0.3% and a Reynolds number of 10,005 over water data. The pressure
drop, pumping power, friction factor penalty are 17.05%, 15.96%, and 14.29%, at 0.3% particle concentration
and a Reynolds number of 10,005, compared to water. The effectiveness and number of transfer units are
increased by 2.49% and 2.75% at 0.3% particle concentration and a Reynolds number of 10,005 compared to
water data. The cost, weight, embodied energy, and CO2 emissions are analyzed based on the enhanced effectiveness
of the heat exchanger. The total embodied energy from the heat exchanger using water is 403.7 MJ and
it reduced to 393.1 MJ with 0.3% nanoparticle concentration. The heat exchanger cost is reduced to 61.46$ using
0.3 vol % of nanofluid whereas it is 63$ using water. The environmental CO2 emissions released from the heat
exchanger are reduced to 81 kg of CO2 using 0.3 vol % of nanofluid, whereas it is 83.3 kg of CO2 using water.