An experimental investigation of the effect of using non-Newtonian nanofluid-graphene oxide/aqueous solution of sodium carboxymethyl cellulose-on the performance of direct absorption solar collector

To improve the performance of direct absorption solar collectors (DASCs), high photo-thermal potential in nanofluids have always been of interest to researchers. Therefore, the present study mainly aimed to use graphene oxide nanofluids due to their high optical absorption capability and excellent dispersion stability. The novelty of this study is the investigation of the special effects of the optical properties of graphene oxide and the thermal potential of non-Newtonian shear-thinning nanofluids together to improve the photo-thermal conversion performance of the DASC model. For this purpose, Non-Newtonian and Newtonian nanofluids, involving graphene oxide nanoparticles, dispersed in sodium carboxymethyl cellulose and deionized water as base fluid, respectively, were prepared and experimentally tested. The flow rate and weight percentage along with incident radiation have been selected as test parameters for estimating the efficiency of the collector. The results showed that the efficiency improvement by increasing the weight percentage of nanoparticles in both nanofluids. Furthermore, by changing the base fluid from Newtonian to non-Newtonian, the reduction in efficiency at 0.01wt% is by (9.4-15.63) % and at 0.03wt% is by (19.84-26.46) %. Additionally, graphene oxide nanofluid sample (S3) was found appropriate for the designed DASC model due to its optimum efficiency and temperature rise rate.