Efficiency enhancement in a triangular solar flat plate collector by using Al2O3- water nanofluids: An experimental study

In this research, a flat plate solar collector with a triangular geometry, which is designed and built by the author and based on the ASHRAE93-2010 standard, has been experimentally studied. The triangular solar collector has no riser and has spiral tubes containing fluid from the inlet to the outlet of the collector. To study water and Al2O3-water nanofluid in concentrations of 0.1, 0.2 and 0.3% and different flow rates from 0.0063 to 0.0378 lit/s have been used, which has been studied experimentally based on environmental criteria such as temperature and radiation and effective thermal parameters such as concentration and flow. Studies show that the triangular solar collector, due to its stable geometry and due to the reduction of the tube length in relation to the area, has a suitable performance for water heaters and can also be used. Time constant for triangular solar collector was between 2.5-4.5 minutes in flow rate ranges. The average efficiency increase when using nanofluids instead of water was about 12.4% and the maximum efficiency obtained at a concentration of 0.3% and a flow rate of 0.0378 was more than 68.3%. Also, in measuring the pressure drop in the collector, it was found that the pressure drop was very small and less than 0.1 bar.