Experimental assessment of solar collector performance enhancement using a surfactant‐stabilized MWCNT –copper ( II ) oxide hybrid nanofluid

This experimental study evaluates the thermal and second‐law performance of a flat‐plate solar collector operated with CuO nanofluids and MWCNT–CuO hybrid nanofluids under actual outdoor conditions. The hybrid suspension was formulated using equal mass proportions of MWCNT and CuO nanoparticles and examined at concentrations of 0.2, 0.4, and 0.6 vol.%. Data were collected between 09:00 and 15:00 h to determine the heat‐transfer behavior, thermal efficiency, and exergy efficiency of the collector. Throughout the experimental period, the MWCNT–CuO hybrid nanofluid demonstrated better performance than both water and the corresponding CuO nanofluid. The maximum heat‐transfer coefficient of 368.5 W m −2 K −1 was achieved using the hybrid nanofluid at 0.6 vol.%. At the peak solar irradiance of 1076 W m −2 , the collector attained a thermal efficiency of 84% and an exergy efficiency of 3.1%. These values indicate a substantial enhancement compared with operation using water as the base fluid. The enhanced collector response can be associated with the complementary thermal and optical characteristics of MWCNTs and CuO nanoparticles, which could contribute to improved thermal transport and utilization of incident solar radiation. The improved collector response can be attributed to the complementary thermal and optical characteristics of MWCNTs and CuO nanoparticles, which facilitate more efficient thermal transport and increased utilization of incident solar radiation. The findings demonstrate that the MWCNT–CuO hybrid nanofluid, particularly at 0.6 vol.%, is a promising heat‐transfer medium for improving the thermal and thermodynamic performance of flat‐plate solar collectors under practical outdoor operating conditions.