Thermal performance, embodied energy and environmental CO2 emissions analyses for double pipe U-bend heat exchanger working with MWCNT/water nanofluid

Abstract

The thermal performance, embodied energy, and environmental CO2 emissions are evaluated experimentally for 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.