Performance analysis of a minichannel-based solar collector using different nanofluids

Abstract

In this paper, an analytical analysis has been performed to evaluate the performance of a minichannel-based solar collector using four different nanofluids including Cu/water, Al2O3/water, TiO2/water, and SiO2/water. The analysis of first and second laws is conducted for turbulent flow by considering the constant mass flow rate of nanofluid. The results are presented for volume fractions up to 4% and nanoparticle size of 25nm where the inner diameter of the risers of flat plate collector is assumed to be 2mm. Analysis of the first law of thermodynamics reveals that Al2O3/water nanofluids show the highest heat transfer coefficient in the tubes while the lowest value belongs to SiO2/water nanofluids. The highest outlet temperature is provided by Cu/water nanofluids, and after that TiO2/water, Al2O3/water, and SiO2/water nanofluids are in ranks of second to fourth. The results of second law analysis elucidate that Cu/water nanofluid produces the lowest entropy generation among the nanofluids. It is found that although the effective thermal conductivity of TiO2/water nanofluids is less than Al2O3/water nanofluids, but the entropy generation of TiO2/water is lower than Al2O3/water. Finally, some recommendations are given for future studies on the applications of nanofluids in solar collectors.