Investigation of energy performance in a U-shaped evacuated solar tube collector using oxide added nanoparticles through the emitter, absorber and transmittal environments via discrete ordinates radiation method

This work is a three-dimensional numerical study of a U-shaped evacuated tube solar collector employing different types of oxide nanofluids including water-Al2O3, water-CuO and water-TiO2 under the steady-state condition. The simulation is performed using the single-phase method for nanofluid modeling, the DO method for radiation modeling, incompressible and fluid flow laminar regime. The thermo-physical properties of the water are considered as a function of temperature ranging from 0 to 150 degrees C. The obtained results showed that increasing both length and diameter of the U-shaped tubes of the solar collector enhances its thermal efficiency. Moreover, it is found that using oxide nanofluids results in an enhancement in the collector thermal performance which using water-CuO nanofluid causes 13.8, 1.5 and 1.3% higher collector thermal efficiency in comparison with employing pure water, water-TiO2 and water-Al2O3 nanofluids, respectively. It is also observed that the working fluid heat capacity plays an important role in the thermal performance of the evacuated tube solar collector.