Improving environmental performance of a direct absorption parabolic trough collector by using hybrid nanofluids

This study deals with the influence of hybrid nanofluids i.e., a mixture of Al2O3 and Multi-wall carbon nanotubes (MWCNTs) dispersed in water, on the environmental performance of a direct absorption parabolic trough collector. For this purpose, hybrid nanofluids in three volume concentrations i.e., 0.01%, 0.02%, and 0.04% were prepared and their optical properties were measured. Next, the nanofluids were used in the direct absorption parabolic trough collector (DAPTC) as a heat transfer fluid (HTF) to measure the effect of using hybrid nanofluids on its energy and environmental performances. Obtained data from the spectrometric experiment reveal that hybrid nanofluids have better optical properties than mono nanofluids and the base fluid, it would be suitable for use in the DAPTC in order to increasing the thermal performance. Using hybrid nanofluids with a volume fraction of 0.04% as the heat transfer fluid intensifies the maximum temperature difference parameter of the solar collector at 240.7%, 57.2%, and 8.2% compared to water, 0.04% alumina nanofluids, and 0.04% MWCNT nanofluids, respectively. Consequently, by using hybrid nanofluids, the thermal efficiency of the solar collector ameliorates by 197.1%, 69.2%, and 6.1% compared with cases in which water, alumina/water (0.04%), and MWCNT/water (0.04%) are used, respectively. The pressure drop in the absorber tube was gaged, and the results show that the increment of pressure drop for hybrid nanofluids can be negligible due to low volume fraction. Moreover, the saving of water along with other contaminants emissions such as CO2 was calculated for the nanofluid-based collector. The results reveal that using hybrid nanofluids instead of water leads to reductions in CO2 emission and water consumption as much as 450.33 kg and 2016.6 m(3) per collector, respectively.

Automated summary

The study demonstrates that hybrid nanofluids have better optical properties than mono nanofluids and can enhance the thermal efficiency of direct absorption parabolic trough collectors. By using hybrid nanofluids, significant improvements in reducing CO2 emissions and water consumption are achieved compared to using water as a heat transfer fluid.