Factors affecting the thermal performance of the flat plate solar collector using nanofluids: A review

Exploitation of solar energy is one of the most significant solutions for facing the current energy management dangers. Flat plate solar collector (FPSC) is one of the most important applications of solar energy in different domestic applications. The use of nanofluids in FPSCs, due to their superior thermo-physical properties, makes it an effective way to enhance the performance of FPSCs. This paper sequentially reviews the studies carried on metal, metal oxides, semiconductor crystalized oxides, and carbon based nanofluids used as heat transfer fluid (HTF) within FPSCs. Various parameters that affect thermal performance of the FPSC such as type of nanoparticle, nanoparticle concentration, nanoparticle size, and mass flow rate of the nanofluid are extensively analyzed in this review. The studies examine different types of single nanofluids or hybrid nanofluids with the FPSC at the same operating conditions are also discussed. Based on the results reviewed in this work, it is revealed that a significant improvement in energy and exergy efficiencies of the FPSC have been obtained by using carbon based nanofluids compared to metal oxides nanofluids under the same conditions. It is also found that the copper oxide nanofluid is the best amongst the metal oxides nanofluids as it improves the efficiency by 6.3–37.3% compared to conventional fluids when it is used with concentration varied from 0.025 to 2%, and mass flow rate ranges from 1 to 8.8 kg/min. A noteworthy observations, proportionalities, and future trends for each nanostructure type are also discussed with detailed and comparative approach.