The Comparison of Thermal and Hydrodynamic Performance between Graphene Oxide and Alumina Nanofluids Operated in a Plate Heat Exchanger

The aim of this experimental study is to investigate the thermal and hydrodynamic performance of graphene oxide and alumina nanofluids with two types of nanoparticle shapes in a plate heat exchanger. The nanofluids with a weight fraction of 0.1% were prepared by dispersing nanoparticles in pure water via a probe ultrasonic apparatus and a vigorous mechanical mixer. Then, the thermo-physical properties of the nanofluids including thermal conductivity and viscosity were analyzed and compared. For the thermal test, a heating system including a brazed plate exchanger equipped with two pumps, two flowmeters, four thermometers, two storage tanks, and insulated steel tubes was set up. The flow rate of hot fluid (pure water) was fixed and the nanofluid was used as cold fluid to cool the hot fluid at flowrates of 1.5, 2, 2.5, 3, and 3.5 L/min. Thermal and hydrodynamic performance was investigated by calculating heat transfer rate, Nusselt number, friction coefficient, pressure drop, pumping power, and finally the performance coefficient criterion (the ratio of heat transfer obtained to pumping power consumed). In comparison with water, the highest enhancement in heat transfer was obtained at the lowest flow rate of graphene oxide and alumina nanofluids to the extent of 46% and 18 %, respectively. This study showed that the maximum performance index was related to the graphene oxide nanofluid at flowrates less than 2.5 L/min, while at flowrates higher than 2.5 L/min, the performance index of graphene oxide nanofluid showed a significant drop and was lower than alumina nanofluid.