Entropy analysis of the unsteady Darcian nanofluid flow in a cylindrical pipe with a porous wall

Abstract

This work examines the entropy generation of nanofluids flowing through a porous medium in a permeable pipe. Water-based suspensions with Cu, Al2O3 and TiO2 as nanoparticles are used as working fluids. These fluids have been found to have enhanced heat transfer characteristics which can be beneficial in various applications such as refrigeration, engine cooling and optimising heat transfer systems. The equations governing the flow system are formulated, and the solution is obtained using the Runge–Kutta–Fehlberg scheme. Results obtained in this flow regime provide unique insight into the flow quantities. Alumina-water is relatively efficient and performs much better regarding heat transfer efficiency and entropy minimisation. However, it exhibits the highest skin friction at the pipe wall. This result is more enhanced when the nanoparticles' solid volume fraction is increased. Irreversibility due to heat transfer is more pronounced and becomes dominant near the pipe wall when the nanoparticles' solid volume fraction is reduced.