Thermal analysis of parabolic trough collector operating with mono and hybrid nanofluids

In this paper, the use of mono and hybrid nanofluids in parabolic trough collectors is investigated. The LS-2 PTC module is studied for operation with Syltherm 800 as the base fluid, while the examined nanofluids are the following: 3% Al2O3/Oil, 3% TiO2/Oil and 1.5% Al2O3-1.5% TiO2/Oil. As it is obvious, in all the cases the total volumetric nanoparticle concertation has the same value in order to perform a suitable comparison. The analysis is conducted for turbulent flow conditions with a flow rate equal to 150 l/min, a value which leads to sufficient thermal performance results. The solar collector is investigated for inlet temperatures from 300 K to 650 K in order to cover a great range of possible operating temperature levels. According to the final results, the thermal efficiency enhancement for the hybrid nanofluid reaches up to 1.8%, while it is up to 0.7% with for mono nanofluids. This higher thermal efficiency enhancement is based on the great Nusselt number enhancement for the hybrid nanofluid case which is about 2.2 higher than the respective for operation with pure oil. The analysis is conducted with a developed thermal model in EES (Engineering Equation Solver) which is validated with literature results.