Entropy and heat transfer investigation of Casson–Maxwell, Casson–Jeffrey, and Casson–Oldroyd-B binary nanofluids in a parabolic trough solar collector: a comparative study

In this paper, we compared copper-engine oil Casson–Maxwell, Casson–Jeffrey, and Casson–Oldroyd-B binary nanofluids in a parabolic trough solar collector. Using appropriate similarity variables, the partial differential equations governing nanofluid flow were converted into ordinary differential equations. The resulting nonlinear systems were solved using the shooting method. The numerical results were presented in graphical and tabular forms. We investigated the effects of different parameters controlling the flow on the velocity, temperature, entropy generation, skin friction, and local Nusselt number of the nanofluids. Overall, the Casson–Maxwell and Casson–Jeffrey nanofluid models had better efficiency than the Casson–Oldroyd-B nanofluid model.