The effect of using nanofluid flow into a porous channel in the CPVT under transient solar heat flux based on energy and exergy analysis

Concentrator photovoltaic thermal system is one of the heat and power generation systems that have received special attention in recent decades. In this paper, concentrator photovoltaic thermal cell with the effect of Al2O3 nanofluid flow in porous channel has been investigated under transient heat flux. The system is analyzed from energy and exergy viewpoint, and also the first and second laws of thermodynamics efficiencies are calculated. The governing equations are continuity, Brinkman momentum and energy conservation equations considering the transient solar flux using parabolic dish concentrator over a day in Mashhad city. The numerical modeling is based on the finite element method. The numerical results show that the Nusselt number, normalized temperature and electrical efficiency of the presented model have an acceptable agreement with experimental data. Efficiency of the photovoltaic cell increases with increasing the Reynolds number as the difference between the highest and the lowest efficiency value is 5% at 12 p.m. In addition, with increasing Reynolds number, the first law of thermodynamics efficiency increases due to porosity and permeability effects of the porous channel cooling. The maximum difference between highest and the lowest value for first law efficiency is 49.4% at Re = 110. The second law of thermodynamics efficiency decrease as Reynolds number increases as the highest value is 4.2% and the lowest is 2.8% at Re = 20 and Re = 10, respectively.