Two-phase simulation and environmental consideration of thermo-hydraulic behavior and entropy production of water/TiO2-SWCNT hybrid nanofluid in a U-shaped heat exchanger equipped with needle fins of different sizes

The significance of optimal fuel consumption is crucial due to the lack of energy resources and the need to preserve the environment. Also, it is unavoidable and toxic for nanoparticles to be released into the environment, as a result of their widespread use. In this study, performance evaluation criteria (PEC), and entropy production of a U-shaped tube heat exchanger with internal fins are numerically examined in the presence of hybrid nanofluid flow. The hybrid nanofluid is water/TiO2-SWCNT. The volume fraction of nanoparticles (φ) changes from 0 to 4% and the considered Reynolds numbers (Res) are 10000, 12500, 15000, 17500, and 20000. The height of needle fins is 1 and 1.25 mm. As Re and fin size are enhanced, the average Nusselt number (Nu) is intensified. For the fin size of 1.25 cm, the maximum enhancement in the PEC is 8.45% when φ is enhanced from 0 to 4% and Re=10000. For the fin size of 1cm, the maximum enhancement in thermal entropy production is equal to 81.5% as the Re is enhanced from 10000 to 20000 and φ=0%. Thermo- hydraulic analysis recommends using a U-shaped heat exchanger with a fin size of 1.25 cm. The use of nanofluid decreased energy consumption, emissions, and damage to the environment.