Thermohydraulic optimization of artificial roughness in photovoltaic-thermal (PVT) system using genetic algorithm

The photovoltaic-thermal system is a solution for using solar energy to produce both electric and thermal power. In the present study, artificial curved roughness is used in the collector flow channel to investigate its effect on the performance of the system. The effect of artificial roughness characteristics, working fluid type and Reynolds number on thermohydraulic perfor-mance is investigated by numerical simulation and optimization of the system. The results show that the addition of artificial roughness in laminar and turbulent flow deteriorates and enhances the thermohydraulic performance of the system, respectively; so that the maximum performance improvement is achieved at the beginning of the considered range of the turbulent flow. The maximum thermohydraulic performance is related to geometry with a roughness angle of 30 degrees, a relative height of 0.04, and a relative pitch of 16. In addition, changing the working fluid from water to nanofluid, as well as increasing the flow rate, increases the system overall efficiency. For instance, using water-based Ag-MgO and CNT nanofluids in the Reynolds number of 10, the system overall efficiency is %64.74, %67.73, and %74.69, respectively. The results of multi -objective optimization based on genetic algorithm show that the best thermohydraulic perfor-mance, electrical and thermal efficiency are 1.203, %9.68, and %75.79, respectively, which are obtained in Reynolds number of 3537 for water-based CNT nanofluid. Also, the optimum Rey-nolds numbers using water and water-based Ag-MgO nanofluid are 4046 and 3936, respectively.