Energy, exergy, and hydrodynamic performance of a spiral heat exchanger: Process intensification by a nanofluid containing different particle shapes

Abstract

The energy, exergy, and hydrodynamic characteristics of employing a boehmite alumina nanofluid inside a spiral heat exchanger are investigated through CFD analysis regarding five different nanoparticle shapes. The numerical simulations are performed at four different volume fractions ranging from 0 to 0.04. It is found that utilizing the nanofluid at a higher volume fraction enhances the heat exchange amount, overall heat transfer coefficient (U), and effectiveness. It is unveiled that the highest rise in the U at the constant Reynolds number (Re) is about 25.4%, while this value at the constant pumping power (W˙) is 6.35%. Additionally, concerning the thermal efficiency viewpoint, it is proposed to use the platelet-shaped nanoparticles at the constant Re. The oblate spheroid-shaped nanoparticles are suggested considering the energy efficiency perspective. Based on the second law of thermodynamics, the platelet-shaped particles demonstrate the best performance at the invariant Re, while at the constant W˙, the oblate spheroid-shaped nanoparticles are recommended. The thermal irreversibility of the nanofluid in the case of constant Re only reduces using the oblate spheroid-shaped nanoparticles. The smallest exergy destruction in the case of constant Ẇ belongs to the blade-shaped nanoparticles.