Investigating exergy destruction and entropy generation for flow of a new nanofluid containing graphene-silver nanocomposite in a micro heat exchanger considering viscous dissipation

The second law attributes including entropy generation, exergy destruction and second law efficiency for flow a novel nanofluid containing graphene nanoplatelets decorated with silver nanoparticles are investigated in a micro double-pipe heat exchanger. The effects of viscous dissipation are considered in the simulation. Frictional entropy generation intensifies with increase in Reynolds number and concentration. Moreover, with the concentration increment, thermal entropy generation rate increases. The frictional and thermal exergy destruction rates intensify in both tube and annulus sides by increasing either Reynolds number or concentration. The results show that the friction has a more significant role than heat transfer in exergy destruction occurred in the heat exchanger. By increasing the Reynolds number, contribution of the nanofluid side to the exergy destruction increases in comparison with that of the water side. In addition, the second law efficiency decreases by increasing either Reynolds number or concentration. (C) 2018 Elsevier B.V. All rights reserved.