investigating the thermal performance of a nano-fluid based flat - plate solar collector

Solar thermal energy is a renewable, convenient source and environmentally benign energy resource. flat-plate solar collectors are the most common and cost-effective devices for exploiting and converting solar energy into heat and transfer the heat to a medium. however, the efficiency of these systems is not favorable due to the poor thermo-physical properties of working fluid. using nano-fluid is proposed as an efficient method in order to improve the heat transfer properties of the working fluid. adding nanoparticles to base fluid, leads to enhancement in thermal properties of working fluid. thermo-physical properties of base fluid depend on several parameters including particle concentration and size. in this study, the effect of these parameters is theoretically investigated on the thermal performance of a flat-plate solar collector. in addition, the collector efficiency is evaluated for different shapes of the cross-section of the riser pipe. it is observed that increase in nanoparticle volume fraction, enhances the efficiency of a flat-plate collector and the maximum obtained value was approximately 80%. reversely, particle size increase from 20 nm to 80 nm, causes more than 3% reduction in the efficiency. in addition, for different shapes of the pipe cross-section, including circle, square, and triangle; circular cross sections leads to the highest efficiency in a flat-plate solar collector