Evaluation of Thermophysical Properties and Thermal Performance of Amine-Functionalized Graphene Oxide/Deep Eutectic Solvent Nanofluids as Heat-Transfer Media for Desalination Systems

Abstract

The study mainly focuses on the synthesis and characterization of amine-functionalized graphene oxide (GO-NH2) nanoparticles. It also reports the thermal properties and stability analysis of deep eutectic solvent (DES)- and GO-NH2- based nanofluids. DES is composed of diphenyl ether as the hydrogen bond acceptor and DL-menthol as the hydrogen bond donor in the molar ratio 1:1. The nanofluid was prepared by a two-step method where two different concentrations of functionalized graphene nanofluids, namely, 0.0033 volume fraction (NF1) and 0.0101 volume fraction (NF2), were reported. XRD and FTIR analyses were used to validate the nanoparticle’s identity. Additionally, the morphology and composition of GO-NH2 nanoparticles were investigated using FESEM, FETEM, EDS, and Raman analyses. After that, the stability of the nanofluids was assessed using ζ potential measurements. The ζ potential measurements revealed increased stability, indicating that no agglomeration occurred in the DES-based nanofluid. Excellent thermal conductivity enhancement was observed at a higher temperature for the GO-NH2 nanofluid. The density and viscosity of the base fluid and nanofluid decreased with an increase in temperature from 25 to 85 °C. Further, the specific heat capacity of the nanofluids also increased with the increase in temperature and volume fractions of the nanofluid. Thermogravimetric analysis was also performed to evaluate the thermal degradation of the nanofluid under a nitrogen atmosphere. The nanofluid was used in brine recirculation multistage flash desalination where the gained output ratio of less than 10 was obtained through ASPEN simulation.