Simultaneous energy storage enhancement and pressure drop reduction in flat plate solar collectors using rotary pipes with nanofluid

Abstract

Abstract Flat plate solar collectors waste a massive part of the heat accumulated near the contact region, mainly due to poor thermal characteristics of working fluid. The demanding power for pumping the flow through the pipes seems a permanent concern in solar collectors. Also, active methods seem not to be applicable in such systems due to the external energy requirement and cost associated with it. An innovative and simple technique is considered here to eliminate such deficiencies all at once by equipping the flat plate collector with rotary absorber pipes and Fe3O4/water nanofluid. Results indicate that the applied method improves the convection mechanism in each pipe by mixing the accumulated heat in the whole flow regions and saves more available solar energy. It also reduces the pressure drop by preparing a slip flow condition inside the pipes, thereby reducing the consuming pumping power. Results also reveal that by dispersing 2% Fe3O4 in water and utilizing rotary pipes one can restore around 1.65% and 10.44% of the energy loss of the collector, respectively. In other words, additional energy of 120.16 W can be stored by equipping a flat plate solar collector with rotary tubes and Fe3O4/water nanofluid. Also, equipping the collector by both rotary pipes and nanofluid causes 5.83% and 3.21% enhancement in energy and exergy efficiencies, respectively. The reported results substantiate that the required power for operating the employed method can be provided by the collector itself, which makes the proposed technique more cost-effective.