Assessment of a heat pipe solar collector with nanofluids.

This research was designed to experimentally study the influence of using three metal oxide nanofluids at different high flow rates with various mass concentration of nanoparticles as the working fluid, on the thermal efficiency and pumping power of heat pipe solar collector (HPSC). The volume flow rate of the working fluid was 5, 8, 11, and 14 L/min. Also, mass concentration of nanoparticles was 0.5 and 1.167 g/L. Co-precipitation technique was employed to prepare CuO, AlO, and MgO nanoparticles. The optical and structural characterization of the nanostructure were considered by using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and UV-visible analysis. The thermal performance of the HPSC using metal oxide nanofluids and water was compared with the volume flow rate that varied from 5 to 14 L/min. It was observed that nanofluids improved the collector efficiency between 9 and 20% compared with deionized water. The present results revealed that the maximum efficiency was found to be 83% for a mass concentration of 1.167 g/L of CuO nanofluids and volume flow rate of 14 L/min. The HPSC efficiency shows better improvement with the increasing mass concentration of metal oxide nanoparticles and volume flow rate. Also, the increase rate of the pumping power and pressure drop is less than 0.9% for all of the nanofluids that were used as the working fluids. Results showed that the metal oxide nanofluids are appropriate for increasing the efficiency of HPSC.