Exergy distribution characteristics of solar-thermal dissociation of NiFe2O4 in a solar reactor

Abstract

Exergy is an efficient tool for evaluating the quality of energy, and it plays an important role in reducing irreversible losses, improving energy efficiencies, saving energy sources and reducing pollution emissions for energy utilization systems. This study furthered an investigation of exergy distribution characteristics of NiFe2O4 solar-thermal dissociation in the solar reactor using User Define Function (UDF) technique in Fluent. The analysis was based on the previous results including temperature, velocity and species concentration during the solar thermal dissociation of NiFe2O4 in a solar reactor. In addition, the effects of reactant particle diameter, particle flow rate and aperture gas temperature on the physical and chemical exergy distributions were also studied. The results showed that with the increasing in particle diameter, a lower physical exergy region gradually forms around the axial centerline in the solar reactor and the value of chemical exergy decreases sharply. Both the increasing in particle mass flow rate and aperture gas temperature reduce the low value of physical exergy distribution and increase the value of chemical exergy due to the high conversion rate. There is an increasing limitation for mass flow rate of particles and gas temperature. But the increasing limitation needs further investigation by considering coupling the effects of the above operating parameters. The results obtained from this study gave basic knowledge of exergy distribution characteristics for solar-thermal dissociation processes and found a theoretical basis for structural optimization of solar reactors.