Numerical simulation of nanofluid in central tube of solar collector by two-phase mixture approach

In this study, a new idea was proposed to enhance the direct absorption of radiation by the nanofluid by incorporating a central absorber copper tube. Copper oxide (CuO) nanoparticles were used as the nanofluid with mass percentages of 0.05%, 0.055%, and 0.01% by weight, mixed with an oil-based fluid. The absorption coefficients were varied in the range of 10, 40, and 100. The performance of the collector was compared to experimental and numerical data from other literature. Based on the results, the presence of the central copper tube inside the absorber tube of the collector led to higher radiation absorption under the same conditions compared to the nanofluid alone. In the case of the highest nanofluid composition (0.055% by weight), the thermal efficiency increased by up to 7% compared to a standard direct absorption collector.For an absorption coefficient of 10, the proposed collector exhibited the largest difference in output temperature compared to the usual volumetric absorption collector (DATPSC), with a temperature difference of approximately 23 K. To obtain more accurate results, the fluid domain in the parabolic collector with the new configuration was numerically investigated using ANSYS software.