No abstract

One of the main problems that limit the extensive use of photovoltaic (PV) systems is the increase in the temperature of PV panels. Overheating of a PV module decreases the performance of the output power by 0.4% to 0.5% per 1°C over its rated temperature that in most cases is 25°C. An effective way of improving electrical performance (power output and efficiency) and reducing the rate of thermal degradation of a PV module is to reduce the operating temperature of the PV surface by a cooling medium. To achieve this, nanofluids can be considered as a potentially effective solution for cooling. In this study, two types of nanofluids, namely Al2O3 and TiO2 water‐based mixture of different volume flow rates and concentrations (0.01%, 0.05%, and 0.1%) by weight, were used. Also, three PV panels were cooled simultaneously using nanofluids, water, and natural air, respectively. Results showed that nanofluids for cooling enhanced heat transfer rate much better than water and natural air. Best results were achieved for TiO2 nanofluids at the considered concentration (0.1 wt%). Nanofluid cooling of turbulent flows for such an application has not been investigated before. These results represent the first application of nanofluid cooling in the turbulent flow regimes and in outdoor conditions including real solar irradiation.

Different volume concentrations (1.2, 0.6, 0.3 wt%) of Fe3O4/water nanofluids and for different Reynolds number (Re) varying from 2180 to 9160 were used experimentally. The aim of work is to study the effect of applying various magnetic field intensity 15.1, 30.3, 45.5 mT on heat transfer enhancement in a horizontal pipe heated with constant heating flux of 420 W. Results showed that Nusselt number (Nu) increases with increasing Re for the nanofluids and water regardless the presence or absence of the magnetic field. Also, higher values were obtained than water. The average increase in Nu for Fe3O4-nanofluids is 16.7% relative to water when the magnetic field is not applied. However, the average increase in heat transfer coefficient and Nusselt number are 9.4%, 26.1%, 31.3% and 8.8%, 13.1%, and 23.9% in the presence of magnetic field [Formula: see text] compared to the absence of magnetic field and base fluid water, respectively. Furthermore, pressure drop increases with the increase of Reynolds number and magnetic field strength. It can be concluded that the magnetic field has a big effect on the thermal transfer performance of Fe3O4/water nanofluid when compared with the thermal motion of magnetic nanoparticles. Finally, it is found that the performance factor is above unity in the presence and absence of magnetic field strength. This means that Nusselt number enhancement is higher than friction changes, which indicates the applicability of the heated pipe in the improvement of heat transfer. These results can be useful for enhancing heat transfer in many engineering applications such as heat exchangers, medical devices, and electronic devices.