Second law analysis of a nanofluid-based solar collector using experimental data

The present study deals with the entropy generation analysis of a flat-plate solar collector using SiO2/ethylene glycol-water nanofluids. For this purpose, available experimental data on the performance of a flat-plate solar collector are exploited for estimating the entropy generation in the system. Ethylene glycol-water (EG-water) and EG-water-based nanofluids having three different nanoparticle volume fractions including 0.5, 0.75, and 1 % are considered as the working fluids. The results are presented in terms of exergy efficiency, entropy generation parameter, and Bejan number for three different mass flow rates and various solar radiation intensities. It is found that when nanofluid concentration increases from 0 to 1 %, exergy efficiency enhances up to 62.7 % for a mass flow rate of 1 L min(-1), whereas the corresponding increases in mass flow rates of 1.75 and 2.5 L min(-1) are 45.2 and 39.7 %, respectively. The results also elucidate that entropy generation parameter, which is a function of entropy generation, ambient temperature, and solar radiation, reduces with increasing the nanofluid concentration.