Thermal performance evaluation of a nanofluid-based flat-plate solar collector: An experimental study and analytical modeling

The thermal performance of a flat-plate solar collector (FPSC) is investigated experimentally and analytically. The studied nanofluid is SiO2/deionized water with volumetric concentration up to 0.6% and nanoparticles diameter of 20-30nm. The tests and also the modeling are performed based on ASHRAE standard and compared with each other to validate the developed model. The dynamic model is based on the energy balance in a control volume. The system of derived equations is solved by employing an implicit finite difference scheme. Moreover, the thermal conductivity and viscosity of SiO2 nanofluid have been investigated thoroughly. The measurement findings indicate that silica nanoparticles, despite their low thermal conductivity, have a great potential for improving the thermal performance of FPSC. Analyzing the characteristic parameters of solar collector efficiency reveals that the effect of nanoparticles on the performance improvement is more pronounced at higher values of reduced temperature. The thermal efficiency, working fluid outlet temperature and also absorber plate temperature of the modeling have been confirmed with experimental verification. A satisfactory agreement has been achieved between the results. The maximum percentage of deviation for working fluid outlet temperature and collector absorber plate temperature is 0.7% and 3.7%, respectively.