Effect of graphene-based nanofluid on heat transfer performance of alternate elliptical axis oval tube heat exchanger

The comparative heat transfer analysis of alternative elliptical axis oval tube (AEAOT) carrying graphene/water-based nanofluids at various volumetric concentrations and operating conditions has been done. The investigation pertains to Reynolds number range, i.e., 100-2000 in AEAOT tube heat exchanger and the inlet temperature of nanofluid is varied from 40 to 70 degrees C. The outer pipe is allowed to flow water, inner pipe (AEAOT) carries nanofluid at different volumetric concentrations (0.02%, 0.04%, 0.06%, 0.08%, and 0.1%), and heat exchanger is subjected to both parallel and counter flow arrangements. The effect of pertinent parameters such as mass flow rate and fluid temperature on the performance of the AEAOT heat exchanger has been studied through numerical investigations. The presence of alternate oval tube enhances the axial vortices resulting in improving the heat transfer performance. Overall heat transfer coefficient is higher for counterflow arrangement, approximately 4.5% more than parallel flow. Moreover, the estimated non-dimensional heat transfer enhancement factor for parallel and counter is in the range of 2.68-2.17 to 2.59-2.06. It is concluded that heat transfer enhancement can be achieved with low concentrations of nanoparticles to avoid excessive pumping requirements in AEAOT heat exchanger.