Thermal performance of a nanofluid-based flat plate solar collector: A transient numerical study

• Published in: Applied thermal engineering 2018-02, Vol.130, p.395-407
• Main Authors: Genc, Alper Mete, Ezan, Mehmet Akif, Turgut, Alpaslan
• Format: Article
• Language: English
• Subjects: Al2O3; Aluminum oxide; Critical flow; Energy efficiency; Energy harvesting; Flat plates; Flat-plate; Mass flow rate; Nanofluids; Numerical analysis; Photovoltaic cells; Reynolds number; Solar collector; Solar collectors; Solar radiation; Studies; Thermodynamic efficiency; Thermophysical properties; Transient analysis; Transient heat transfer; Working fluids
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2017.10.166

•Transient behavior of nanofluid based flat plate solar collector was studied.•Nanofluid increased the outlet temperature by 7.20% compared with water.•Efficiency of the FPSC increases with increasing mass flow rate.•Nanofluid is more effective on the collector efficiency at below 0.016 kg/s.•Transient analyses provide the determination of thermal inertia of FPSC components. Flat plate solar collectors (FPSCs) are commonly used devices to convert solar radiation into useful heat for a variety of thermal applications. Due to the lower thermal efficiencies of these systems, recently, nanofluids are suggested to be used in FPSCs as the working fluid to enhance their energy harvesting potential. This study introduces a transient heat transfer approach for determining the thermal inertia of each component such as glass, trapped air, absorber and working fluid for nanofluid based flat plate solar collectors. The analyses were carried out with water and three different volumetric concentrations of Al2O3 nanoparticles as 1%, 2% and 3%. Mass flow rate of the heat transfer fluid is varied in a wide range, between 0.004 and 0.06 kg/s, to demonstrate the effect of thermophysical properties at different flow Reynolds numbers. The results indicate that the maximum increase of the outlet temperature is obtained by 7.20% at 0.004 kg/s and 3% (vol.) mass flow rate and volumetric concentration, respectively, in July. On the other hand, the highest thermal efficiency is obtained as 83.90% at 0.06 kg/s mass flow rate for 1% (vol.) in October. It is worthy of note that nanofluids can increase the thermal efficiency of the FPSCs at lower flow rates and beyond a critical flow rate the base fluid becomes effective working fluid. For the current study, the critical flow rate is determined to be 0.016 kg/s.