Experimental analysis of thermal performance of direct absorption parabolic trough collector integrating water based nanofluids for sustainable environment applications

Integration of nanofluids with solar collectors to enhance collector's thermal performance stands out as one of the most effective techniques owning to nanofluids favorable thermo-physical properties. By improving the thermo-physical properties of heat transfer fluids, nanofluids enhance the efficiency of thermal systems by improving the thermal energy storage capacity. This experimental study serves as a novel comparison between water-based Al2O3 (Alumina) and Multi-walled Carbon Nanotubes (MWCNTs) nanofluids in such mass concentrations (0.1%, 0.2%, and 0.3%) at fixed mass flow rates of 0.012 kg/s and 0.024 kg/s to investigate the impact on the performance of Direct Absorption Parabolic Trough Collectors (DAPTC) under the arid climatic conditions of Pakistan. The peak thermal efficiencies were found to be 40%, 56% and 58% for distilled water (DW), Al2O3-water and CNTs-water nanofluids, respectively. Thermal efficiency of DAPTC was improved by 18% in comparison with the basefluid alone on account of increased surface area, thermal conductivity and overall heat transfer capabilities. The CNTs-water nanofluids were observed to be more thermal efficient Heat Transfer Fluids (HTFs) owing to the black color and comparatively lower specific heat capacity. These thermal efficient fluids are of great use in the thermal energy storage systems. In addition, the use of nanofluids for heating and cooling purposes in industries is preferable as operational and manufacturing costs can also be lowered by reducing the systems size.