Critical operating parameters of solar flat plate collectors using CuO nanoparticles of different volume fractions subjected to natural convection

A flat plate solar water heater is investigated for its efficiency when water and the copper oxide (CuO) of 20 nm size nanoparticles of varying volume fractions and their performance are studied. A solar water heater with a flat plate collector of dimensions 1 x 0.45 m(2) with 25 liter per day storage tank capacity, which works on the thermo-syphon principle, is fabricated. The collector is run with a base working fluid of deionized water and then with CuO nanoparticles for different volume fractions of 0.2% and 0.4% with a surfactant to study the collector's efficiency. The surfactant used in cetyltrimethylammonium bromide of 1% in working fluid. The rise in temperature and the collector efficiency is compared for different volume fractions of CuO nanoparticles in the collector. The mixing of nanoparticles thus improves the efficiency of the collector. The experimental result shows that the collector with a 0.4% volume fraction of CuO with water as a working fluid has the maximum rise in temperature and efficiency compared with that of 0.2% and water. During the test, CuO without surfactant showed a slight decrement in heat transfer due to the agglomeration. The collector efficiency for 0.4% volume fraction achieves 63.28%, for 0.2% is 61.58%, and for water 54.15%. The overall efficiency was increased by up to 9.1% compared with base conventional fluid water for lower volume fractions of CuO nanoparticles for a smaller collector area.