Thermal and chemical reaction performance analyses of solar thermochemical volumetric receiver/reactor with nanofluid

Abstract

In this paper, a novel solar thermochemical volumetric receiver/reactor with nanofluid is proposed. Thermal and chemical performance analyses of the volumetric receiver/reactor are numerically investigated and compared with those of the conventional surface receiver/reactor. A two-dimensional axisymmetric heat and mass transfer model coupled with reaction kinetics is developed to predict the temperature distribution and reactant conversion ratio. The effects of particle characteristics including size and volume fraction and solar irradiation intensity are discussed. The results indicate that for the nanofluid with a volume fraction greater than 0.005, an optical path depth of 0.015 m is sufficient to absorb almost 100% of the incident solar energy. The volume weighted average temperature of the volumetric receiver/reactor with a volume fraction of 0.05 and particle diameter of 10 nm can reach 506.0 K which is about 8.8 K higher than that of the surface receiver/reactor leading to a 5.2% increase of the outlet methanol conversion ratio from 56.9% to 62.1% under a typical operating condition. The methanol conversion ratio increases with the reduction of nanoparticle size and the increment of the volume fraction and solar irradiation intensity. The thermochemical efficiency has a maximum value of 48.9% when solar irradiation intensity is 600 W/m2.