Experimental and numerical analysis of convective heat transfer and entropy generation of graphene/water nanofluid in AEAOT heat exchanger

Abstract

Background:Effective utilization of nanofluid's potential and optimal heat exchanger design is paramount in addition to heat transfer enhancement. A novel alternate elliptical tube is fabricated, and graphene nanofluids are chosen to enhance the convective heat transfer characteristics. Methods:The experimental setup is validated with circular pipe results before conducting graphene nanofluid experiments. The finite volume method was adopted to conduct simulation results, and its validation was done with the experimental results. The results of numerical simulations are compared with experiments, and the obtained mean percentage error (MPE) is 1.17%, 8.71%, 8.05% and 8.85% for water, G0.05%, G0.1% and G0.2%, respectively. Experiments are conducted at different mass flow rates and inlet temperatures of nanofluid. Significant findings: The oval tube in an alternate direction improves the secondary flow region with a high swirl, leading to a smaller thermal boundary layer thickness. Nusselt number enhances as an average of 10.3%, 29.2% and 39.1% for graphene nanofluids prepared using weight concentrations 0.05%, 0.1% and 0.2%, respectively, at 80 °C. The effect of inlet temperature reveals heat transfer coefficient and Nusselt number increase and 1.57, 1.88, 2.16 times than water is observed for G0.05%, G0.1% and G0.2%, respectively. Pertinent to entropy generation, Bejan number (Be) decrease with graphene nanoparticle concentration; as inlet temperature increases, corresponding fluid friction irreversibilities are observed as 18.4%, 24.6% and 36.4% for G0.05%, G0.1% and G0.2% nanofluids, respectively. The present work caters for the importance of AEAOT design which prompts heat transfer enhancement; indeed, optimization of transition length and aspect ratio are essential to overcome the pressure loss cost.