Influence of Nano Fluid and Receiver Tube Shape Modification on the Performance of Solar Parabolic Trough Collector with Closed System

Solar energy is one of the cleaner forms of renewable energy resources which achieve the need of people in the field of thermal energy. The parabolic trough solar collector is one of the most efficient and it has been studied widely. Direct absorption solar collector is a new technique used recently in harvesting solar energy. In this study, non-circulated Nano-Fluid (N-F) is used to absorb the solar radiation through a glass wall in parabolic solar collector closed system. In this study N-F is pure water with nano copper oxide. The nanoparticles used were 32 nm copper oxide particles with concentration of 0.05 %. The absorbed heat was directly transferred to circulated water flowing inside a copper tube submerged in the N-F. In addition to the absorption of solar radiation from the N-F, the heat transfer flowing through the walls was made into the water. There were two shapes for the copper tube of the receivers, the first was helical and the second was straight and they have the same surface area. A study of the effect of changing the volumetric flow rate and temperature of the inlet fluid on the efficiency of the new configuration was performed. The results show that Helical Tube (HT) has efficiency more than Straight Tube (ST) especially when using N-F. It is also found that N-F in direct absorption system with direct heat exchange improves the performance of solar collector. In addition, direct heat exchange within the solar receiver has reduced the overall thermal resistance of the solar collector system. The increase in the volumetric flow rate increased the Reynolds number.