Alireza Rahbari

Mixed convection analysis of variable heat source/sink on MHD Maxwell, Jeffrey, and Oldroyd-B nanofluids over a cone with convective conditions using Buongiorno’s model

This paper investigates the mixed convection of MHD Maxwell, Jeffery, and Oldroyd-B nanofluid models with heat source/sink over a cone geometry. The nonlinear ordinary differential equations are solved numerically by using Runge–Kutta-based shooting technique for transformed systems. Moreover, the non-homogenous Buongiorno’s model is employed, which accounts for both the impact of thermophoresis and Brownian motion of the nanofluids. The accuracy of the numerical data is obtained by comparison against the existed results in the literature. Furthermore, the effects of important physical parameters such as thermophoresis, Biot number, Brownian motion, and magnetic field parameters on the concentration, temperature, and velocity profiles are evaluated in this research. As the vital outcome of this research, it is revealed that the heat and mass transfer rates are more significant in Jeffery model than other two models Maxwell and Oldroyd-B nanofluid models.

Thermodynamic modelling and solar reactor design for syngas production through SCWG of algae

Conversion of algal biomass into value added products, such as liquid fuels, using solar-assisted supercritical water gasification (SCWG) offers a promising approach for clean fuel production. SCWG has significant advantages over conventional gasification in terms of flexibility of feedstock, faster intrinsic kinetics and lower char formation. A relatively unexplored avenue in SCWG is the use of non-renewable source of energy for driving the endothermic gasification. The use of concentrated solar thermal to provide the process heat is attractive, especially in the case of expensive feedstocks such as algae. This study attempts to identify the key parameters and constraints in designing a solar cavity receiver/reactor for on-sun SCWG of algal biomass. A tubular plug-flow reactor, operating at 24 MPa and 400-600 °C with a solar input of 20MWth is modelled. Solar energy is utilized to increase the temperature of the reaction medium (10 wt.% algae solution) from 400 to 605 °C and simultaneously drive the gasification. The model additionally incorporates material constraints based on the allowable stresses for a commercially available Ni-based alloy (Inconel 625), and exergy accounting for the cavity reactor. A parametric evaluation of the steady state performance and quantification of the losses through wall conduction, external radiation and convection, internal convection, frictional pressure drop, mixing and chemical irreversibility, is presented.Conversion of algal biomass into value added products, such as liquid fuels, using solar-assisted supercritical water gasification (SCWG) offers a promising approach for clean fuel production. SCWG has significant advantages over conventional gasification in terms of flexibility of feedstock, faster intrinsic kinetics and lower char formation. A relatively unexplored avenue in SCWG is the use of non-renewable source of energy for driving the endothermic gasification. The use of concentrated solar thermal to provide the process heat is attractive, especially in the case of expensive feedstocks such as algae. This study attempts to identify the key parameters and constraints in designing a solar cavity receiver/reactor for on-sun SCWG of algal biomass. A tubular plug-flow reactor, operating at 24 MPa and 400-600 °C with a solar input of 20MWth is modelled. Solar energy is utilized to increase the temperature of the reaction medium (10 wt.% algae solution) from 400 to 605 °C and simultaneously drive the gasi...