Investigation of factors influencing the performance of nanofluid-based direct absorption solar collector using taguchi method

Abstract

The performance of nanofluid-based solar collector depends on different factors like nanoparticle material, base fluid, mass fraction of nanoparticles, height of the collector, length of the collector, incident solar flux, mass flow rate of the nanofluid in the collector. In order to quantify the effect of nanoparticle material, optical properties of different nanofluids (different nanoparticles dispersed in DI water) were measured using spectrophotometer. After studying the optical signatures of the nanofluids, solar-weighted absorptivity of the nanofluids was calculated to evaluate the efficient nanoparticle material for harnessing solar irradiation. It has been found that amorphous carbon nanoparticles-based fluid has highest absorptivity at low mass fractions and is suitable for harnessing solar energy. Further, the performance of nanofluid-based solar collector has been investigated numerically using amorphous carbon nanoparticles. For the purposes of this analysis, a twodimensional steady-state heat transfer model has been developed for a collector in which the nanofluid flows horizontally and is heated with normally incident solar irradiation. During the analysis carried out in this study, five factors were chosen (height of the collector, nanofluid mass flow rate, solar irradiation incident flux, nanoparticle mass fraction, and length of the collector). The influence of variation in these five factors on the overall performance of the solar collector (i.e., outlet temperature) was analyzed using the Taguchi method. In order to carry to this analysis, the values of these five factors were varied at three levels. Based on these variations, the L18 standard orthogonal array was prepared, and the matrix containing the 18 sets of combinations was organized. The results showed that two factors (length of the collector, and the incident solar flux) exhibited a strong increasing trend, while one factor (nanoparticle mass fraction) exhibited an optimizing trend on the output (outlet collector temperature). Further, from the calculations it has been observed that 60 mg L-1 is an optimum mass fraction at which maximum collector efficiency can be achieved for the length of the collector (= 1 m), height of the collector (= 10 mm), incident flux (= 1000 W m-2 ), mass flow rate (= 0.010 kg s-1 ).