Numerical analysis of heat transfer in flat-plate solar collector with nanofluids

Heat transfer aspects of a typical flat-plate solar collector utilizing water-based nanofluids as the working fluid were analyzed numerically. Water-based nanofluids of various compositions containing metallic Al2O3 and Cu nanoparticles with volume fractions ranging from 1% to 5% were examined, and the effects of the nanofluids on the heat transfer were quantified. Relevant parameters such as the heat flux, the Reynolds number, and the collector tilt angle were calculated and compared to each other at different boundary conditions. The flat-plat solar collector geometry was simplified, and only a fluid carrying pipe with an absorber surface was chosen as a numerical model with a particular attention to symmetry, instead of taking the entire collector geometry. The numerical model was controlled and confirmed by applying it to similar studies existing in the pertinent literature. All numerical solutions were carried out by using a commercial finite volume software package called ANSYS Fluent. Two schemes of the heat transfer taking place between the fluid and the surrounding surface were employed in the analysis. One is the mixed convection and the other is the forced convection. Both convection schemes were performed under the same boundary conditions to better understand the effects of the convection. The results show that the nanofluids increase the heat transfer rate ranging from 1% to 8%, when compared to water as a working fluid. The mixed convection was compared to the forced convection to understand the effects of the natural convection. It can be seen from the results that the natural convection effects are too important to be neglected. Keywords: Flat-Plate Solar Collector, Nanofluid, Finite Volume Method, Mixed Convection, Forced Convection, Natural Convection Effects