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 °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.