Effects of CuO/water nanofluid on the efficiency of a flat-plate solar collector

• For any particular working fluid, there is an optimum mass flow rate which maximizes the collector efficiency.
• The highest heat absorption by the collector occurs at different mass flow rates for water and CuO nonofluid.
• Nanoparticles often enhance the thermal characteristics of the base fluid.
• An optimum value of the mass flow rate may be obtained in each individual condition.

Solar water heating is an effective method for heat demands in domestic applications. Solar collector is a main component of any solar water heating system. In this work, the effect of CuO–water nanofluid, as the working fluid, on the performance and the efficiency of a flat-plate solar collector is investigated experimentally. The volume fraction of nanoparticles is set to 0.4% and the mean particle dimension is kept constant at 40 nm. The working fluid mass flow rate is varied from 1 to 3 kg/min. The experiments are conducted in Mashhad, Iran with the latitude of 36.19°. The experimental results reveal that utilizing the nanofluid increases the collector efficiency in comparison to water as an absorbing medium. The nanofluid with mass flow rate of 1 kg/min increases the collector efficiency about 21.8%. For any particular working fluid, there is an optimum mass flow rate which maximizes the collector efficiency. Adding nanoparticles to a base fluid produces a nanofluid which has enhanced thermal characteristics compared with its base fluid.