Energy, Exergy, and Economic Investigation of the Effect of Nanoparticle Mixture Ratios on the Thermal Performance of Flat Plate Collectors Using Al2O3–ZnO Hybrid Nanofluid

Abstract

The study evaluated the effects of nanoparticle mixture ratios on the thermal performance of a flat plate collector (FPC) fitted with a torque stirrer operating with Al2O3–ZnO/water nanofluid. Al2O3 and ZnO nanoparticles with an average size of 29 and 70 nm, respectively, were used to synthesize Al2O3–ZnO/water nanofluid at 1∶1 (50% by volume Al2O3 and 50% by volume ZnO), 2∶1 (66.66% by volume Al2O3 and 33.34% by volume ZnO), and 1∶2 (33.34% by volume Al2O3 and 66.66% by volume ZnO) mixture ratios using a two-step synthesis method. Correlation models were developed for the specific heat capacity, thermal conductivity, and viscosity properties of the hybrid nanofluid based on experimentally obtained data. Meteorological data from Nicosia, Cyprus were used to develop a model to observe the effect of a range of temperatures, volume concentrations, and mass flow rates on the performance of the collector. An economic analysis was performed on the system to observe the cost implications of using the hybrid nanofluids to its efficiency gains. The results showed that the mixture ratio of the nanoparticles in the hybrid nanofluids affects both the thermal and exergetic performance of the collector. The thermal efficiency of the FPC increased with the mass flow rate. The highest efficiency recorded in the collector for all mixture ratios of the hybrid nanofluid was at a 0.1% volume concentration. Accounting for the work done by the torque stirrer, there was a net energy gain in the system; however, the economic analysis showed that nanofluids are more beneficial when used in large-scale installations.