Numerical investigation on using of nanofluid in a water-cooled photovoltaic thermal system

Photovoltaic thermal collector or PV/T is a new hybrid technology that produces heat and electricity simultaneously. The objective of the current study is to evaluate the effects of utilizing nanofluid on the performance of PV/T system. The considered coolant fluids in the simulation are pure water, Ag-water nanofluid and Alumina-water nanofluid. The proposed model includes a water riser tube and an absorber plate to consider the conduction and convection heat transfer mechanisms. The numerical results were obtained using the computational fluid dynamics (CFD) by employing conjugate heat transfer. The effects of the nanoparticle volumetric concentration and inlet fluid velocity on the efficiency and heat transfer enhancement were simulated. In this paper, the Second Law analysis of a water-cooled PVT is also represented, based on results of simulations. The results show that the efficiencies (the first and second laws of thermodynamics) and heat transfer coefficient increase by increasing the nanoparticle volume fraction. The maximum increase percentage of heat transfer coefficient versus volume fraction for alumina-water and Ag-water nanofluid are 12% and 43%, respectively. Increasing the inlet fluid velocity improves the heat transfer performance of PV/T system. Increasing the heat transfer coefficient with respect to the inlet fluid velocity for alumina-water nanofluid at phi = 5% was in the range of 8-10%, in comparison to pure water. While this value for Ag-water nanofluid at the same volumetric fraction is significantly greater than alumina-water, which varies from 28 to 45%. For the purpose of validating the results of the presented method, a comparison study was carried out with the experimental results in the literature. The comparison shows an appropriate agreement with the results of the literature. (C) 2016 Elsevier Ltd. All rights reserved.